Some audio purist still claim that solid-state amplification is not truly hi-fi in comparison to it’s thermionic / vacuum tube counterpart, is there a reason behind this?
By: Ringo Bones
During the start of the 1970s, the solid-state transistor-based audio power amplifier started to make the price of high-powered hi-fi amplifiers – i.e. over 50-watts – much more affordable. But many hardcore audiophiles complained that transistor-based audio power amplifier didn’t sound as musical as their thermionic / vacuum tube-based counterparts. Even newer MOSFET devices – whose characteristic curves resembles that of a pentode tube – still didn’t sound quite as musical in comparison to their thermionic brethren during their rollout near the end of the 1970s. But is there a reason – hopefully a scientifically verifiable one – that explains why solid-state amplification (transistors and MOSFETS) don’t sound as good as their vacuum tube counterparts?
Back in the summer of 1997, a French amplifier manufacturer – Lavardin Technologies – announced that they have discovered why solid-state amplification didn’t sound as musical as their vacuum tube-based competition. They called the phenomena “Memory Distortion” which Laverdin Technologies describes it during 1997 as “the greatest discovery in analogue audio design in the previous twenty years”. Memory distortion, Lavardin Technologies says, is responsible for the shrillness and mechanical-sounding artifacts identified in solid-state amplifiers. Unfortunately in the intervening years, my “richer” audio-buddies can only listen to Lavardin Technologies’ amplifiers in hi-fi shows because they are so prohibitively expensive when compared to vacuum tube-based amplifiers of similar power output and features. But they swear that Lavardin Technologies' low-powered integrated amps do sound like they use vacuum tubes as power output devices.
Fast-forward in 2009 when one of my audio-buddies managed to purchase one used – although still very costly – one of those Lavardin Technologies integrated amplifier. It is the 30-watt Lavardin IS Reference which sells for almost 4,000 US dollars when brand new. He got one for a shade under 2,000 US dollars, and say’s its all worth it because the single-pair of transistors used in this integrated amp will last for thousands of years when properly used. And they do sound like vacuum tube amps – vacuum tube amps that could drive speakers with tricky impedance curves. Albeit only within their “meager” 30-watt rating. But despite of the obvious overpricing in electronics engineering terms, why do these amps sound so good?
Given our sample no longer has the company’s warranty and my audio-buddy was generous enough – albeit up to a point – to allow our local hi-fi association a peak inside the innards of Lavardin’s famed integrated amps. A look inside might make every “mainstream” electronic engineers accuse of Lavardin Technologies of recto-cranial inversion. Those mainstream folks usually accuse everyone of encasing the circuits of their designs in some kind of black goop in the name of copyright protection, as suffering from recto-cranial inversion. But these has been proven – probably since the 1980s – that it could improve the sound quality by controlling spurious vibrations from affecting the sensitive circuit layout.
Lavardin did divulge the reason why tubes sound better than transistors, which they used to their advantage in making their solid-state amplifiers sound as good as tubes. It was probably the consensus view of quantum physicists who looked into the differences in operation of vacuum tubes and solid-state devices during the 1990s. According to their findings – though it has been noted in every post World War II vacuum tube-based electronic textbook in existence – which start at the basic fundamental differences between vacuum tubes and solid-state devices.
In a vacuum tube any particular electron – i.e. strictly speaking the electron’s wave function – travels through free space, influenced only by the electric fields caused by the various electrodes in the electron’s wave function’s path within the confines of the tube. The control grid’s field hold’s back a proportional number of electrons from the total number of electrons emitted by the cathode, in which a change in grid voltage change’s it’s field and thereby varies the total number of electrons reaching the anode and hence the resulting anode current.
The velocity of an electron by the time it reaches the anode after being accelerated by the anode’s field is truly mind-boggling. As an example, a tube with a typical anode voltage of 450-volts, the electrons will hit the anode at approximately 28 million miles per hour or about 4% the speed of light – which is around 670 million miles per hour in vacuum. Thus the reason for the vacuum tube’s somewhat high-temperature operation. The electrons which make it past grid are the same ones which – a tiny fraction of a second later – appear at the anode and becomes the signal that drives the load.
In a solid-state device – transistors, MOSFETS, and specially including wire – the electrons have a very hard time traversing the entire length of their intended path. In the solid-state domain, electrons have to fight their way through millions of random fields caused by the atoms in the substrate material – usually at 0.001 meters per second. In which calling it a snail’s pace would be an understatement in comparison to an electron’s speed traveled though a typical vacuum tube. Furthermore, it is not the actual electrons which carry the signal, but the influence one electron on it’s neighbors. The message or signal gets carried akin to a “Chinese Whisper” albeit only with less degradation of the signal – hopefully.
This quantum-mechanical explanation of the radical difference between vacuum tubes and solid-state devices is the claim used by Lavardin in explaining how they minimized memory distortion in their solid-state amplifier designs. According to them, memory distortion has to do with the way musical signals have to slog their way through silicon – akin to being stuck in the mud. Transistors hold previous signals in memory – as in the electron’s wave function. And these “residual memories” or remnants of an electron’s previous state - maybe a few tiny fractions of a second before distort the new incoming signals. The musical signals can’t flee the silicon fast enough. But is this explanation sufficient from a scientific standpoint? After all, if “memory distortion” is about timing errors – assuming that the phenomenon is real in the first place – then why is it that there are several, albeit almost unrelated, ways of eliminating the symptoms caused by memory distortion.
James Henriot of Whest Audio also managed to do the same feat of making solid-state amplifiers more musical by eliminating “analog-domain jitter” via his Whest dap.10 processor. Which most users testify that the Whest dap.10 processor improves their already well-sorted CD playback system’s sound quality by making it sound like a big analog open-reel tape, the one often used in better recording studios. I’ve heard this only in hi-fi shows, but my impression of this product seems like it makes your typical solid-state integrated amp sound like a good vacuum tube amp.
While a Frenchman named Yves-Bernard André of YBA also manages to do the same with his solid-state integrated designs by using various techniques holistically to eliminate the symptoms that make solid-state amplifiers sound “inferior” to their vacuum tube counterparts. From using synthetic diamond powder to damp the circuit boards to the resonance control of every component used. Not to mention minimizing to the absolute minimum the inherent hystersis distortion caused by a transistor’s ferromagnetic enclosure. Even though YBA products – as with most French integrated amps - are typically priced way above a typical hi-fi enthusiast is willing to pay, Yves-Bernard André’s holistic approach to designing his solid-state based audio components seems to have removed the symptoms of what we know of as memory distortion.
LFD Mistral MOSFET-based integrated amplifiers also managed to eliminate the symptoms of memory distortion through attention in circuit layout. By orienting the resistors of their LFD Mistral integrated amps in phase on the master board. The resistors on both channels are identically oriented which they believe – and some owners of LFD Mistral integrated amps – is important to stereo imaging. So does the orientation of the wiring and the fuses. Unfortunately, this attention to detail in parts layout doesn’t lend itself well to mass production machinery used in making mobile / cellular phones and i-Pods. But the resulting product is nonetheless spectacular. LFD Mistral integrated amplifiers are often compared to single-ended triode amplifiers in terms of sound quality.
So what does this all mean? Well, it seems like the holistic tweaking techniques utilized by Yves-Bernard André and the LFD Mistral does seem to improve the sound quality of your typical solid-state audio gear – even ones using integrated circuit IC amplifiers. While the Lavardin Technologies may be on to something in explaining the phenomenon of memory distortion, James Henriot’s forays into analog-domain jitter will probably need the collaboration of other scientist with access to the very state of the art testing gear to explore further the phenomena of analog-domain jitter. Who knows that it might result in better and cheaper laptops and mobile phones ten years from now? Maybe memory distortion is just a symptom of bad circuit layout in the production of solid-state gear. Often easily solved via enclosing critical parts in a faraday cage - or by the use of exotic and boutique capacitors like Rubycon Black Gates or Philips-sourced French Blue capacitors.
Wednesday, October 28, 2009
Tuesday, September 22, 2009
Is the BBE Sonic Maximizer Hi-Fi?
Manufactured during the mid 1980s supposedly as a means to “transcend” the limitations of hi-fi speakers at that time, does the BBE Sonic Maximizer qualifies back then – and now – as hi-fi?
By: Ringo Bones
Now (as in 2009) derided by hardcore audiophiles and “soulful” electric guitar players, I did remember during my high-school days – i.e. the mid 1980s – that a black box with the letters BBE was both revered and coveted in domestic hi-fi circles in my neck of the woods. To the uninitiated – and those who have already forgotten – here’s a refresher of that used to be wonderful black-box known as the BBE Sonic Maximizer.
The letters BBE stands for Barcus-Berry Entertainment Incorporated – later called BBE Sound Inc. when they’re “iconic” black-box / audio processor that became widely used and endorsed by Heavy Metal musicians during the “Hair Metal” era of the late 1980s and early 1990s. The company is located at Huntington Beach, California. Around the middle of the 1980s, BBE Sonic Maximizers began to be widely used for audio recording, motion picture sound tracks, TV and radio broadcasting, and motion picture theatre sound systems. According to the audio processor’s creators, BBE Sonic Maximizers were primarily designed to improve the sonic clarity of virtually any reproduced sound by correcting / compensating for phase and amplitude distortions produced as your typical power amplifier drives a typical loudspeaker system.
My first hand experience of this device was back in 1987 when a rich high-school classmate with similar musical tastes as me got one from his dad while working in the US. It was the Barcus-Berry BBE Model 2002 signal processor, which sold around 500 US dollars at the time. The BBE signal processor was meant to be installed between the signal source(s) – we only had a cassette tape deck and a Technics Quartz Synth tuner at the time – and the power amplifier.
Though my memories of that particular BBE Sonic Maximizer was now somewhat hazy, I can still vividly remember that we often played a track called Digital Bitch by W.A.S.P. (We Are Sexual Perverts?) at the time - Unforgettable because Chris Holmes, Blackie Lawless and the rest of the band probably foresaw the rise of Paris Hilton and her famous antics on the Internet. And as one of the few Heavy Metal bands who gained a strong following in the Punk community – my high-school classmate was actually into Punk / New Wave at the time – W.A.S.P. gained fame (or is it notoriety?) in both camps. Rumor has it that W.A.S.P. were “discovered” by Ed McMahon during the first season of Star Search.
From my present perspective – being my present hi-fi set-up is composed mainly of Electro-Harmonix vacuum tube-equipped and high-speed wide-band solid state exotica. All I can say is that the BBE Sonic Maximizer is nothing more than a “lazy-EQ”. I mean it is just an adjustable Loudness controller on steroids – though I am not denying that it is not useful. Given that at the time, we can rarely crank up our hi-fi sets to “unamplified / no PA system” garage band sound levels. Those rare occations when we can play as loud as possible during my high-school days is usually reserved for band practice.
When you can only play your hi-fi below the actual sound pressure level the music was originally recorded, Loudness and other EQ / tone controls to compensate the Fletcher-Munson Equal Loudness Contour Curves inherent to how our ears perceive airborne sound. To my ears – back then as it is now (2009) – BBE Sonic Maximizers boosts the bass and treble frequencies of the audio signal, depending on how much it’s “process” knob is being cranked.
First impressions on using the BBE Sonic Maximizer usually results in “clarity” – i.e. the boosting of the high-frequency signals usually around 2-KHz to 3-KHz upwards. And this is why many novice hi-fi enthusiasts during the early 1990s who can only afford mass market mini component boom boxes to listen to their copies of Smells Like Teen Spirit by Nirvana became concerned over “tweeter failure”. Especially when the tweeters of their BBE-equipped boom boxes (which became commonly widespread around 1992) heats up when playing the iconic “Seattle Grunge” album that features very distorted electric guitar sound with boosted high-frequencies.
Due to its endorsement and use by top musicians, like Megadeth and Skid Row – guitarists Dave “The Snake” Sabo and Scotti Hill were known to use one - during the early 1990s. The folks at BBE Sound Inc. created a BBE Sonic Maximizer plug-in for PC-based recording, which started to gain popularity during the late 1990s. For domestic hi-fi use, the BBE Sonic Maximizer works very well with budget cassette tape decks that don’t carry the Nakamichi badge to make them sound more “natural”. BBE Sonic Maximizers also works very well to "improve" (...or is that to flatter?) the “sound quality” of FM stations that are seriously addicted to those OPTIMOD compressors. And data reduced digital music downloads like MP3s. But if it is up to me, I would rather use the vacuum tube-based Pultec Model EQP-1R studio equalizer. This vintage studio equalizer - probably dating back to The Beatles era Abbey Road Studios - has 12RX7 and 12RU7 preamplifier vacuum tubes that can put to shame the BBE in sound quality terms.
Unfortunately, BBE Sonic Maximizers are an anathema to vacuum tube hi-fi aficionados and “soulful” electric guitar players because they tend to make their gear sound like cheap solid state. Like a brand new 10,000-watt audio power amplifier with a manufacturer’s suggested retail price of 200 US dollars. Surprisingly, BBE Sonic Maximizers can often be found in pawnshops or other establishments that sell pre-owned music gear somewhere between 50 to 100 US dollars. So it is somewhat a cost-effective way for the curious and uninitiated to experiment – or experience first-hand - what this BBE audio processing brouhaha is all about.
By: Ringo Bones
Now (as in 2009) derided by hardcore audiophiles and “soulful” electric guitar players, I did remember during my high-school days – i.e. the mid 1980s – that a black box with the letters BBE was both revered and coveted in domestic hi-fi circles in my neck of the woods. To the uninitiated – and those who have already forgotten – here’s a refresher of that used to be wonderful black-box known as the BBE Sonic Maximizer.
The letters BBE stands for Barcus-Berry Entertainment Incorporated – later called BBE Sound Inc. when they’re “iconic” black-box / audio processor that became widely used and endorsed by Heavy Metal musicians during the “Hair Metal” era of the late 1980s and early 1990s. The company is located at Huntington Beach, California. Around the middle of the 1980s, BBE Sonic Maximizers began to be widely used for audio recording, motion picture sound tracks, TV and radio broadcasting, and motion picture theatre sound systems. According to the audio processor’s creators, BBE Sonic Maximizers were primarily designed to improve the sonic clarity of virtually any reproduced sound by correcting / compensating for phase and amplitude distortions produced as your typical power amplifier drives a typical loudspeaker system.
My first hand experience of this device was back in 1987 when a rich high-school classmate with similar musical tastes as me got one from his dad while working in the US. It was the Barcus-Berry BBE Model 2002 signal processor, which sold around 500 US dollars at the time. The BBE signal processor was meant to be installed between the signal source(s) – we only had a cassette tape deck and a Technics Quartz Synth tuner at the time – and the power amplifier.
Though my memories of that particular BBE Sonic Maximizer was now somewhat hazy, I can still vividly remember that we often played a track called Digital Bitch by W.A.S.P. (We Are Sexual Perverts?) at the time - Unforgettable because Chris Holmes, Blackie Lawless and the rest of the band probably foresaw the rise of Paris Hilton and her famous antics on the Internet. And as one of the few Heavy Metal bands who gained a strong following in the Punk community – my high-school classmate was actually into Punk / New Wave at the time – W.A.S.P. gained fame (or is it notoriety?) in both camps. Rumor has it that W.A.S.P. were “discovered” by Ed McMahon during the first season of Star Search.
From my present perspective – being my present hi-fi set-up is composed mainly of Electro-Harmonix vacuum tube-equipped and high-speed wide-band solid state exotica. All I can say is that the BBE Sonic Maximizer is nothing more than a “lazy-EQ”. I mean it is just an adjustable Loudness controller on steroids – though I am not denying that it is not useful. Given that at the time, we can rarely crank up our hi-fi sets to “unamplified / no PA system” garage band sound levels. Those rare occations when we can play as loud as possible during my high-school days is usually reserved for band practice.
When you can only play your hi-fi below the actual sound pressure level the music was originally recorded, Loudness and other EQ / tone controls to compensate the Fletcher-Munson Equal Loudness Contour Curves inherent to how our ears perceive airborne sound. To my ears – back then as it is now (2009) – BBE Sonic Maximizers boosts the bass and treble frequencies of the audio signal, depending on how much it’s “process” knob is being cranked.
First impressions on using the BBE Sonic Maximizer usually results in “clarity” – i.e. the boosting of the high-frequency signals usually around 2-KHz to 3-KHz upwards. And this is why many novice hi-fi enthusiasts during the early 1990s who can only afford mass market mini component boom boxes to listen to their copies of Smells Like Teen Spirit by Nirvana became concerned over “tweeter failure”. Especially when the tweeters of their BBE-equipped boom boxes (which became commonly widespread around 1992) heats up when playing the iconic “Seattle Grunge” album that features very distorted electric guitar sound with boosted high-frequencies.
Due to its endorsement and use by top musicians, like Megadeth and Skid Row – guitarists Dave “The Snake” Sabo and Scotti Hill were known to use one - during the early 1990s. The folks at BBE Sound Inc. created a BBE Sonic Maximizer plug-in for PC-based recording, which started to gain popularity during the late 1990s. For domestic hi-fi use, the BBE Sonic Maximizer works very well with budget cassette tape decks that don’t carry the Nakamichi badge to make them sound more “natural”. BBE Sonic Maximizers also works very well to "improve" (...or is that to flatter?) the “sound quality” of FM stations that are seriously addicted to those OPTIMOD compressors. And data reduced digital music downloads like MP3s. But if it is up to me, I would rather use the vacuum tube-based Pultec Model EQP-1R studio equalizer. This vintage studio equalizer - probably dating back to The Beatles era Abbey Road Studios - has 12RX7 and 12RU7 preamplifier vacuum tubes that can put to shame the BBE in sound quality terms.
Unfortunately, BBE Sonic Maximizers are an anathema to vacuum tube hi-fi aficionados and “soulful” electric guitar players because they tend to make their gear sound like cheap solid state. Like a brand new 10,000-watt audio power amplifier with a manufacturer’s suggested retail price of 200 US dollars. Surprisingly, BBE Sonic Maximizers can often be found in pawnshops or other establishments that sell pre-owned music gear somewhere between 50 to 100 US dollars. So it is somewhat a cost-effective way for the curious and uninitiated to experiment – or experience first-hand - what this BBE audio processing brouhaha is all about.
Monday, September 14, 2009
An Op-Amp IC For Your Hi-Fi Needs?
Given that they’ve been used successfully in a number of excellent sounding hi-fi applications, is there really a right op-amp for your audiophile needs out there?
By: Ringo Bones
Yes it’s true, there really is such a thing as an audiophile grade integrated circuit operational amplifier or IC op-amp. And most of them are not necessary manufactured by Analog Devices like the AD845 and AD843. Or those by Burr-Brown which their dual op-amps that are specified to be fast enough to handle the RF energy present in Red Book CD digital to analog conversion are often used in bridge configuration in left / right analog outputs.
The quest for finding the best off the shelf IC op-amp probably started during the early 1990s. When major CD player manufacturers discovered – either by theoretical introspection or trial and error – that those high-speed op-amps made their 500 US dollar or so CD players sound closer to entry-level audiophile grade vinyl LP replay.
From the electronic engineer’s design standpoint, high-speed op-amps are a necessity in Red Book specification CD players. Sufficient slew rate ratings are a necessity to handle the quite large amounts of ultrasonic requantization noise - which is an unfortunate by-product of converting your 16-bit 44.1-KHz digital data into a reasonably smooth analog waveform that could sufficiently past muster as music. In my experience with the most widely used up-market “hi-fi” op-amps – namely the LM318 and the LF356 – which have very different personalities when used in an audiophile context. Although I used audiophile grade ceramic IC sockets with silver connectors to allow me to easily replace both op-amps for comparison.
Over the years, my countless experiences with the high-slew rate (50 volts per microsecond) LM318 suggests that this IC op-amp is well suited to audiophiles who like to listen to Classical Music - Or wants to reproduce the recorded hall acoustic of an opera recording accurately played back in his or her listening room. It even enhances – or exaggerates – the Classical Music-like hall acoustics of some tracks of The Gathering’s “How To Measure A Planet?” album.
One drawback of the LM318 op-amp though is that it doesn’t like very much the “relatively” high-capacitance interconnects often used in entry-level solid-state audio gear. Like Monster Cable’s mellow sounding M850i interconnect often used to tame the harshness of cheap solid-state audio systems. Resulted in a high-pitched squealing sound on rare occasions (guaranteed more than once) during turn on. Although easily remedied by turning off and turning on again your entry-level solid-state amp.
Even though from a technical standpoint, the LF356 has a much lower slew rate rating (12 volts per microsecond) in comparison to the LM318, it does audiophile-oriented things that the LM318 can only aspire to. The very high input impedance – about 1 trillion ohms - of the JFET input stage of the LF356 allows it to have a bass response that Rock Music aficionados since the time of Elvis strive for. The LF356 is also capable of driving large capacitive loads – up to 10,000 picofarad or 0.01 microfarad – with ease. Which makes it more suitable for driving high-capacitance mellow sounding interconnects used in entry-level solid state gear.
Sound quality wise, it is as if the designer of the LF356 op-amp want it to sound like what recording engineer Andy Johns wants the first four album of Led Zeppelin to sound like – i.e. the “John Bonham snare sound”. The LF356 also sound as if it is the first op-amp with a very musically ideal loudness control. It defeats the Fletcher-Munson contour curve characteristic of the human ear that makes us less sensitive to the bass and treble frequencies when listening at reduced sound volume levels. With the LF356, you’ll get the full works whether you’re playing at 65dB or 95dB sound pressure levels - not unlike the sound of Electro-Harmonix versions of 12AX7 preamplifier tubes.
Surprisingly, the LF356 does room sound too - Although not like the Classical Music concert hall portrayed by the LM318. The room sound produced by the LF356 is the “normal” unadorned type – typical recording studio or just a spacious venue. The LF356 also has better low-level sound retrieval in comparison to the LM318 because the LM318 tends to exaggerate the dynamic range of CDs that are recorded without Tom Lord-Alge levels of compression. Like Lunachick’s Binge and Purge album which the LF356 still manages to retrieve low-level details that are played back even softer by its higher slew rate counterpart.
Both can still benefit from a well-regulated plus and minus 15 volt split supplies though, given the inherent RF corruption of our contemporary power lines. Despite both IC op-amps often rated with a power supply rejection ratio of over 100dB at 50 to 60-Hz AC. Boutique capacitors like Rubicon Black Gate capacitors or Philips sourced French Blue capacitors also help improve sound quality to no end.
So there you have it, two op-amps that I have extensive experience with that could past muster as being audiophile certifiable. Although it is somewhat over simplistic to conclude that one prefers Rock, while the other op-amp prefers Classical. The sound quality of one is sufficiently different from the other that it is worth noting. Although the LF356 also has a gorgeous presentation with Orchestral Classical Music recorded during the Golden Age of Stereo.
By: Ringo Bones
Yes it’s true, there really is such a thing as an audiophile grade integrated circuit operational amplifier or IC op-amp. And most of them are not necessary manufactured by Analog Devices like the AD845 and AD843. Or those by Burr-Brown which their dual op-amps that are specified to be fast enough to handle the RF energy present in Red Book CD digital to analog conversion are often used in bridge configuration in left / right analog outputs.
The quest for finding the best off the shelf IC op-amp probably started during the early 1990s. When major CD player manufacturers discovered – either by theoretical introspection or trial and error – that those high-speed op-amps made their 500 US dollar or so CD players sound closer to entry-level audiophile grade vinyl LP replay.
From the electronic engineer’s design standpoint, high-speed op-amps are a necessity in Red Book specification CD players. Sufficient slew rate ratings are a necessity to handle the quite large amounts of ultrasonic requantization noise - which is an unfortunate by-product of converting your 16-bit 44.1-KHz digital data into a reasonably smooth analog waveform that could sufficiently past muster as music. In my experience with the most widely used up-market “hi-fi” op-amps – namely the LM318 and the LF356 – which have very different personalities when used in an audiophile context. Although I used audiophile grade ceramic IC sockets with silver connectors to allow me to easily replace both op-amps for comparison.
Over the years, my countless experiences with the high-slew rate (50 volts per microsecond) LM318 suggests that this IC op-amp is well suited to audiophiles who like to listen to Classical Music - Or wants to reproduce the recorded hall acoustic of an opera recording accurately played back in his or her listening room. It even enhances – or exaggerates – the Classical Music-like hall acoustics of some tracks of The Gathering’s “How To Measure A Planet?” album.
One drawback of the LM318 op-amp though is that it doesn’t like very much the “relatively” high-capacitance interconnects often used in entry-level solid-state audio gear. Like Monster Cable’s mellow sounding M850i interconnect often used to tame the harshness of cheap solid-state audio systems. Resulted in a high-pitched squealing sound on rare occasions (guaranteed more than once) during turn on. Although easily remedied by turning off and turning on again your entry-level solid-state amp.
Even though from a technical standpoint, the LF356 has a much lower slew rate rating (12 volts per microsecond) in comparison to the LM318, it does audiophile-oriented things that the LM318 can only aspire to. The very high input impedance – about 1 trillion ohms - of the JFET input stage of the LF356 allows it to have a bass response that Rock Music aficionados since the time of Elvis strive for. The LF356 is also capable of driving large capacitive loads – up to 10,000 picofarad or 0.01 microfarad – with ease. Which makes it more suitable for driving high-capacitance mellow sounding interconnects used in entry-level solid state gear.
Sound quality wise, it is as if the designer of the LF356 op-amp want it to sound like what recording engineer Andy Johns wants the first four album of Led Zeppelin to sound like – i.e. the “John Bonham snare sound”. The LF356 also sound as if it is the first op-amp with a very musically ideal loudness control. It defeats the Fletcher-Munson contour curve characteristic of the human ear that makes us less sensitive to the bass and treble frequencies when listening at reduced sound volume levels. With the LF356, you’ll get the full works whether you’re playing at 65dB or 95dB sound pressure levels - not unlike the sound of Electro-Harmonix versions of 12AX7 preamplifier tubes.
Surprisingly, the LF356 does room sound too - Although not like the Classical Music concert hall portrayed by the LM318. The room sound produced by the LF356 is the “normal” unadorned type – typical recording studio or just a spacious venue. The LF356 also has better low-level sound retrieval in comparison to the LM318 because the LM318 tends to exaggerate the dynamic range of CDs that are recorded without Tom Lord-Alge levels of compression. Like Lunachick’s Binge and Purge album which the LF356 still manages to retrieve low-level details that are played back even softer by its higher slew rate counterpart.
Both can still benefit from a well-regulated plus and minus 15 volt split supplies though, given the inherent RF corruption of our contemporary power lines. Despite both IC op-amps often rated with a power supply rejection ratio of over 100dB at 50 to 60-Hz AC. Boutique capacitors like Rubicon Black Gate capacitors or Philips sourced French Blue capacitors also help improve sound quality to no end.
So there you have it, two op-amps that I have extensive experience with that could past muster as being audiophile certifiable. Although it is somewhat over simplistic to conclude that one prefers Rock, while the other op-amp prefers Classical. The sound quality of one is sufficiently different from the other that it is worth noting. Although the LF356 also has a gorgeous presentation with Orchestral Classical Music recorded during the Golden Age of Stereo.
Monday, September 7, 2009
Are Integrated Circuit Operational Amplifiers Hi-fi?
In the current fashion “revival” of vacuum tube and discrete transistor usage in the hi-fi scene, are audio designs that use integrated circuit op-amps still considered hi-fi?
By: Ringo Bones
Integrated circuit – or IC – op-amps have a myriad of advantages over their discrete component-based counterparts other than space. Like extremely high input impedance, high common mode rejection ratio and high power supply noise rejection ratio just to name a few all in a very compact package. But in terms of ultimate sound quality, many top designers in the hi-fi world find the sound quality of most IC op-amps wanting.
Richard Fryer, founder and owner of Spectral Audio – one of the top manufacturers of cutting edge solid-state audio gear, who as recently as 1998 still insist on using discrete circuitry. As opposed to integrated circuit chips much of the time. Fryer and his design team at Spectral Audio had found out over the years that for critical signal applications, integrated circuits – or IC chips to you and me – simply don’t meet their quality standards. Although he and his design team had been constantly evaluating new integrated circuits and, to everyone’s credit, the IC chips are getting better and better through the years. Still in the rigorous evaluations that the design team at Spectral Audio does these “improved” IC chips simply can’t pass the microphone feed accurately. There’s so much musical information and life that is lost – according to Fryer. Even with the most premium integrated-circuit amplifiers, these integrated circuit packages are just not up to Spectral Audio’s needs in critical signal applications.
Even though most audio designers in the hi-fi world still insist on using discrete components, there are those who are adventurous enough to use IC op-amps in their cutting edge audio designs. Ron Sutherland is one of those high-end audio gear designers who isn’t afraid to use IC op-amps in his almost 7,000 US dollar Sutherland PH-1 phono preamplifier. Maybe it is because Sutherland has a degree in both electrical engineering and physics that made him courageous enough to use a number of Analog Devices instrumentation integrated circuit op-amps on his somewhat “pricey” but very good sounding phono preamplifier.
Another upmarket high-end audio gear that uses IC op-amps is Reflection Audio Design’s 4,700 US dollar (550 US dollar extra for a phono stage) OM1 preamplifier. The OM1 preamplifier is a high-speed, super wide-bandwidth design based on very high slew rate IC op-amps rated at 2,000 volts per microsecond slew rate. It is purported to be flat to 2 megahertz and able to maintain an absolute phase of plus and minus 0.5 degrees across the audio bandwidth (20 Hz to 20,000 Hz). The OM1 preamp by Reflection Audio Design is a very pretty two-chassis affair – if you include the matching 1,550 US dollar battery unit – with a high level of attention to detail. Like the use of curved circuit traces to avoid high-frequency signal reflection.
There are also budget high-end audio designs that used IC op-amps. Like the Super Pas 4 i preamp kit which famed Dynaco tube amp tweaker Frank Van Alstine sold in the early 1990s. Though this preamplifier is somewhat unique because it is a tube and op-amp IC hybrid. Comprising of two 12AX7 tubes and two AD845 (AD843) FET input op-amps in the output stage. And it is surprisingly affordable – in high-end audio terms – at 595 US dollars back in 1993.
In my personal experience, op-amp IC chips – when used properly – can achieve excellent results sound quality wise. Sometimes I wonder why all brand-name boom boxes being flogged in the “high-street” can’t achieve excellent sound quality that matches even cheap DIY hi-fi that uses op-amp chips. Even DIY-ers had achieved excellent results with these lowly audio devices. Most of these serving as a gateway to the wild blue yonder of high-end audio. Next time, I’ll be discussing my experiences with the most touted op-amps for audio use, the LF356 and the high slew rate LM318 in a DIY hi-fi context – replete with unapologetic tweaks.
By: Ringo Bones
Integrated circuit – or IC – op-amps have a myriad of advantages over their discrete component-based counterparts other than space. Like extremely high input impedance, high common mode rejection ratio and high power supply noise rejection ratio just to name a few all in a very compact package. But in terms of ultimate sound quality, many top designers in the hi-fi world find the sound quality of most IC op-amps wanting.
Richard Fryer, founder and owner of Spectral Audio – one of the top manufacturers of cutting edge solid-state audio gear, who as recently as 1998 still insist on using discrete circuitry. As opposed to integrated circuit chips much of the time. Fryer and his design team at Spectral Audio had found out over the years that for critical signal applications, integrated circuits – or IC chips to you and me – simply don’t meet their quality standards. Although he and his design team had been constantly evaluating new integrated circuits and, to everyone’s credit, the IC chips are getting better and better through the years. Still in the rigorous evaluations that the design team at Spectral Audio does these “improved” IC chips simply can’t pass the microphone feed accurately. There’s so much musical information and life that is lost – according to Fryer. Even with the most premium integrated-circuit amplifiers, these integrated circuit packages are just not up to Spectral Audio’s needs in critical signal applications.
Even though most audio designers in the hi-fi world still insist on using discrete components, there are those who are adventurous enough to use IC op-amps in their cutting edge audio designs. Ron Sutherland is one of those high-end audio gear designers who isn’t afraid to use IC op-amps in his almost 7,000 US dollar Sutherland PH-1 phono preamplifier. Maybe it is because Sutherland has a degree in both electrical engineering and physics that made him courageous enough to use a number of Analog Devices instrumentation integrated circuit op-amps on his somewhat “pricey” but very good sounding phono preamplifier.
Another upmarket high-end audio gear that uses IC op-amps is Reflection Audio Design’s 4,700 US dollar (550 US dollar extra for a phono stage) OM1 preamplifier. The OM1 preamplifier is a high-speed, super wide-bandwidth design based on very high slew rate IC op-amps rated at 2,000 volts per microsecond slew rate. It is purported to be flat to 2 megahertz and able to maintain an absolute phase of plus and minus 0.5 degrees across the audio bandwidth (20 Hz to 20,000 Hz). The OM1 preamp by Reflection Audio Design is a very pretty two-chassis affair – if you include the matching 1,550 US dollar battery unit – with a high level of attention to detail. Like the use of curved circuit traces to avoid high-frequency signal reflection.
There are also budget high-end audio designs that used IC op-amps. Like the Super Pas 4 i preamp kit which famed Dynaco tube amp tweaker Frank Van Alstine sold in the early 1990s. Though this preamplifier is somewhat unique because it is a tube and op-amp IC hybrid. Comprising of two 12AX7 tubes and two AD845 (AD843) FET input op-amps in the output stage. And it is surprisingly affordable – in high-end audio terms – at 595 US dollars back in 1993.
In my personal experience, op-amp IC chips – when used properly – can achieve excellent results sound quality wise. Sometimes I wonder why all brand-name boom boxes being flogged in the “high-street” can’t achieve excellent sound quality that matches even cheap DIY hi-fi that uses op-amp chips. Even DIY-ers had achieved excellent results with these lowly audio devices. Most of these serving as a gateway to the wild blue yonder of high-end audio. Next time, I’ll be discussing my experiences with the most touted op-amps for audio use, the LF356 and the high slew rate LM318 in a DIY hi-fi context – replete with unapologetic tweaks.
Sunday, August 9, 2009
Does Cranking the Bias Current Make a Better Tube Amp?
Many swear that it improves high frequency performance, but does cranking up the bias current a sensible way to improve high frequency performance of your tube / valve amplifier?
By: Ringo Bones
This thorny issue started in my neck of the woods during the tube / valve amp revival of the mid-1990s. Where everyone with a still-working 6L6-equipped 1965 Fender twin of a EL34-equipped Marshall amplifier found out that these rock guitar workhorses can be made into very righteous hi-fi amps by jacking up the output tubes’ bias currents and connecting them to domestic hi-fi loudspeakers. And after the news arrived that a fresh batch of tubes / valves are only a plane ride away in neighboring Hong Kong, thus turning every tube-based guitar amp toting guitar hero wannabe curious about hi-fi into ad hoc tube / valve electronic experts almost overnight. The frenzy of everyone in my place born way after astronauts Armstrong and Aldrin first walked on the surface of the Moon scrambling in a Manhattan Project-like zeal to make their tube-based guitar amps do double duty as audiophile quality hi-fi amp-on-the-cheap. Is probably the most surreal manifestation of anachronism I will ever see in my entire life, but does the price of their blissful ignorance worth more than they bargained for?
11 years ago (in 1998), I was in the process of fulfilling my personal tour-de-force of constructing a Black Face Fender Champ on steroids. It was a single-ended guitar amp based on the Russian GM70 transmitter tube / valve that I found for sale rather cheaply – 2 for 15 US dollars – in a garage sale. This rather “gigantic tube” has an anode dissipation of 250 watts and requires a power supply of 1,500 volts DC. The only “substantially expensive” parts of my Black Face Fender Champ on steroids was an output transformer by Audio Note that can handle the GM70’s 1,500 volt DC power supply brought used from an “disenfranchised” hobbyist for about 50 US dollars. And a Japanese-sourced OEM Leslie-type organ speaker cab from the 1970s being heavily discounted by our local flea market because no one ever bought it since it went on display back in 1979. The flea market’s storekeeper very gladly sold it to me for about 20 US dollars. Luckily the other components required for my project amp had been lying around in my spare equipment trunk. It wasn’t long before someone in my neighborhood haggled me to part with it for about 1,000 US dollars.
At the time this was a very good deal because I’ve only probably spent about 250 to 300 US dollars creating my ultimate guitar amp, plus I desperately needed the money to bribe into a lucrative government job to pad my résumé. Sadly the new owner began cranking up the output tube’s bias current to accentuate the Black Face Fender Champ on steroids’ very beautiful high-frequency timbre. Allowing the big tube to fail 7 months later. Coming to his senses, he backed up the bias to normal and the “spare” GM70 tube still played to this day (2009).
By their very nature, tube-based electric guitar amplifiers don’t work particularly well as uncompromising audiophile-grade domestic hi-fi amplifiers. Especially if the musically-inclined user discovers the “virtues” of reducing the negative feedback levels of his or her electric guitar tube amp as a hi-fi amp set-up. Though zero-feedback tube / valve amplifiers are well known for retrieving the subtle nuances of the acoustic environment of recorded music, redesigning your guitar amp’s negative feedback to zero could destroy the tweeters of your domestic hi-fi loudspeakers. Especially since an overwhelming majority of guitar amplifiers output transformers are not purposefully wound to work in a zero negative feedback tube-based amplification circuitry. Let alone designed using a Fast Fourier Transform.
EL34 equipped Marshall amps are the most often tweaked by this method to adopt them for domestic hi-fi use. Most of these types have an H.T. of about 440 volts DC when measured between the plate (pin 3) and the cathode (pin 8) of the EL84 tube / valve. Most EL34 push-pull power amplifiers are fitted with access pins / ports where you can insert the + and – test terminals of your voltmeter / multi-tester / multi-meter to allow you to adjust the bias current of each tube. Usually this is composed of a high-wattage 10-ohm resistor – usually designated as Rs and is connected from the pin 8 of a particular EL34 to the circuit ground. When you attach your voltmeter at this test point, it is effectively in parallel to an internal 10-ohm resistor or the Rs resistor.
Setting your voltmeter / multi-tester to the 1-volt range, if the voltage reading across this point is 500-millivolts or ½ volt, you can use ohms law to compute for the bias current of the particular tube you are measuring – i.e. current = voltage / resistance. Which at 500-millivolts / 10-ohms = 50mA or 50-milliamperes of standing current or bias current. Using this data, you can now compute the EL34 tube’s power dissipation in the amp you are testing. Using Ohm’s law formula to obtain power P=IV or P = 50mA multiplied by 440 volts = 23 watts, which will be the power dissipation of the EL34 tube as used in the particular amplifier design you are measuring. Though the voltage of the H.T. and the resistance value of the Rs resistor could deviate by as much as 10% during normal use.
From a design standpoint, the EL34 tube / valve and its derivatives – like the 6L6, KT77, KT88, 5881, 6550, 6CA7 tubes – were rated by their original manufacturers during the “Golden Age of Stereo” for a maximum anode dissipation of 25 watts and exceeding this rating will drastically shorten tube / valve life. This is so because the excess heat generated by exceeding the tube’s anode dissipation will cause the anode to release what is known as occluded gas, which damages the delicate cathode coating reducing electron emission. Some types of EL34 tubes / valves – especially ones manufactured in Eastern Block countries and China during the 1980s – may also have a low emission to start with and cranking up the quiescent bias current / standing current could cause the tube / valve to saturate on peaks / high-level signals, causing distortion.
Many veteran tube / valve amplifier designers suggest that if you are after extended output tube life, you shouldn’t run EL34-type tubes at over 20 watts of total anode dissipation to lessen the heat generated inside the tube / valve. Unfortunately, cranking up the bias current on these types of tubes usually results in an “improvement” of their high frequency response – i.e. a subjectively much louder high-frequency sound output. Which can be addictive when it comes to tube amps because of their really sweet and grain-free presentation of high-frequency audio information. Some are even known to crank up the quiescent bias currents of the tubes of their EL34s up to 85mA, making the tubes less likely to last more than eight months when use at an average of eight hours a week.
If you want to make the high-frequency response of your tube-based electric guitar amp “seem” louder, do what Queensrÿche does during the late 1980s. Replace the 12-inch Celestion speakers of your Marshall cabs with JBLs. Or if you can afford them 15-inch Leslie-derived organ speakers equipped with a whizzer cone similar to the one used by Jimi Hendrix when he recorded Little Wing in the studio back in 1967.
For those with a more thorough knowledge in tube / valve-based electronics, another method of increasing the high-frequency output of your tube-based electric guitar amplifier is to modify the preamplifier section. The majority of tube-based guitar amps being sold today still use the “conventional” 12AX7-based double-triode phase splitters in their preamplifier sections. The problem with the conventional double-triode phase-splitter is it’s high input capacitance caused by the Miller Effect. This causes high-frequency loading on the input (12AX7-based?) tube and reduces bandwidth, making it very difficult to use appreciable amounts of negative feedback - especially with 6L6 Beam Power Tetrode and EL34 Pentode output tube designs – without instability due to the phase shifts incurred. By the way, negative feedback is a necessity when extracting the maximum output power obtainable of relatively “modern” output power tubes like the 6L6 and the EL34.
Low noise R.F. pentode preamplifier tubes can be used as a better phase splitter in the preamplifier section of tube-based electric guitar amps because a pentode has a very low input capacitance and high gain due to the shielding effect of the screen grid. This means that the capacitance loading on the input tube (12AX7) is greatly reduced, increasing bandwidth and decreasing troublesome phase shifts.
Or if you want the ability to experiment lowering the negative feedback of your electric guitar amp or operating the output power section in triode mode without your amplifier breaking into spurious oscillation. Which could destroy tweeters when you used your tube-based guitar amp as an ad hoc hi-fi tube amp, then use beefier preamplifier tubes like the 5687 tube. The 5687 tube can dissipate 4 watts, it’s dead linear, needs less drive current, and has a low output impedance. Making it able to be used as a driver stage of an inter-stage transformer (Does this remind you of the AN214 driving the inter-stage transformer of an MJ2955-based transformer-coupled booster amp?). If you go with this redesign route, the output tubes of your guitar amp could be configured in self-biased or auto bias mode due to the secondary winding of the driver / inter-stage transformer as opposed to their de rigueur fixed bias configuration.
Auto bias has the advantage of providing automatic compensation of tube variability characteristics, so tube matching and individual bias adjustment will no longer be necessary. Though matched pairs of tubes are still desirable. Auto bias gives that sweet, easy sound tubes possess. Fixed bias gives more power, but a harder sound. In my experience, output tubes of auto-bias configured tube amplifiers tend to last forever. My neighbor’s 300B-based auto-bias amp still uses tubes that he purchased back in 1996 without any degradation in sound quality.
Another way of retaining the de rigueur double-triode preamplifier – i.e. 12AX7 tube-based preamplifier – of your guitar amp is by selecting an output tube designed with a higher mu or a high mu version. I have tried this in the past and it does work but it needs power supply / H.T. circuit modification of your guitar amp. The advantage of this route is that high-mu version of your typical output power tube – like the EL34 and 6L6 – are easier to drive, thus retaining the 12AX7 pre-amp tubes. The caveats include complete redesign of the power supply since high-mu tubes require higher supply voltages than the 450 volts DC needed by your typical output power tube / valve. Some of them needs the power supply / H.T. voltage to be raised to 1,500 volts DC in order to enjoy the maximum benefits of high-mu power tubes. Which can be a problem since power supply capacitors capable of handling 1,500 volts DC are somewhat rare, plus the output transformer needs to be changed to a type that can handle such voltage or your loudspeaker will be turned into a dazzling pyrotechnics display.
Though if you change the choke / inductor filtering the 12AX7 pre-amp tubes to one with a higher inductance – therefore higher DC resistance to lower the incoming voltage supplying the pre-amp tubes, the 12AX7 tubes will be fed with a highly-filtered H.T. DC voltage whose hum is now vanishingly low. Another caveat of this design route is that the output impedance of your guitar amp will now be higher than before – i.e. reduced damping factor – which your amplifiers tonality will be readily be affected by a loudspeaker with a widely-varying impedance curve across the audio band. Although guitar amplifiers that uses minimal amounts of negative feedback and high output impedance are known for their excellent musical performance, so you could probably design an electric guitar amplifier that could double as an excellent sounding domestic hi-fi audio amplifier using this route.
By: Ringo Bones
This thorny issue started in my neck of the woods during the tube / valve amp revival of the mid-1990s. Where everyone with a still-working 6L6-equipped 1965 Fender twin of a EL34-equipped Marshall amplifier found out that these rock guitar workhorses can be made into very righteous hi-fi amps by jacking up the output tubes’ bias currents and connecting them to domestic hi-fi loudspeakers. And after the news arrived that a fresh batch of tubes / valves are only a plane ride away in neighboring Hong Kong, thus turning every tube-based guitar amp toting guitar hero wannabe curious about hi-fi into ad hoc tube / valve electronic experts almost overnight. The frenzy of everyone in my place born way after astronauts Armstrong and Aldrin first walked on the surface of the Moon scrambling in a Manhattan Project-like zeal to make their tube-based guitar amps do double duty as audiophile quality hi-fi amp-on-the-cheap. Is probably the most surreal manifestation of anachronism I will ever see in my entire life, but does the price of their blissful ignorance worth more than they bargained for?
11 years ago (in 1998), I was in the process of fulfilling my personal tour-de-force of constructing a Black Face Fender Champ on steroids. It was a single-ended guitar amp based on the Russian GM70 transmitter tube / valve that I found for sale rather cheaply – 2 for 15 US dollars – in a garage sale. This rather “gigantic tube” has an anode dissipation of 250 watts and requires a power supply of 1,500 volts DC. The only “substantially expensive” parts of my Black Face Fender Champ on steroids was an output transformer by Audio Note that can handle the GM70’s 1,500 volt DC power supply brought used from an “disenfranchised” hobbyist for about 50 US dollars. And a Japanese-sourced OEM Leslie-type organ speaker cab from the 1970s being heavily discounted by our local flea market because no one ever bought it since it went on display back in 1979. The flea market’s storekeeper very gladly sold it to me for about 20 US dollars. Luckily the other components required for my project amp had been lying around in my spare equipment trunk. It wasn’t long before someone in my neighborhood haggled me to part with it for about 1,000 US dollars.
At the time this was a very good deal because I’ve only probably spent about 250 to 300 US dollars creating my ultimate guitar amp, plus I desperately needed the money to bribe into a lucrative government job to pad my résumé. Sadly the new owner began cranking up the output tube’s bias current to accentuate the Black Face Fender Champ on steroids’ very beautiful high-frequency timbre. Allowing the big tube to fail 7 months later. Coming to his senses, he backed up the bias to normal and the “spare” GM70 tube still played to this day (2009).
By their very nature, tube-based electric guitar amplifiers don’t work particularly well as uncompromising audiophile-grade domestic hi-fi amplifiers. Especially if the musically-inclined user discovers the “virtues” of reducing the negative feedback levels of his or her electric guitar tube amp as a hi-fi amp set-up. Though zero-feedback tube / valve amplifiers are well known for retrieving the subtle nuances of the acoustic environment of recorded music, redesigning your guitar amp’s negative feedback to zero could destroy the tweeters of your domestic hi-fi loudspeakers. Especially since an overwhelming majority of guitar amplifiers output transformers are not purposefully wound to work in a zero negative feedback tube-based amplification circuitry. Let alone designed using a Fast Fourier Transform.
EL34 equipped Marshall amps are the most often tweaked by this method to adopt them for domestic hi-fi use. Most of these types have an H.T. of about 440 volts DC when measured between the plate (pin 3) and the cathode (pin 8) of the EL84 tube / valve. Most EL34 push-pull power amplifiers are fitted with access pins / ports where you can insert the + and – test terminals of your voltmeter / multi-tester / multi-meter to allow you to adjust the bias current of each tube. Usually this is composed of a high-wattage 10-ohm resistor – usually designated as Rs and is connected from the pin 8 of a particular EL34 to the circuit ground. When you attach your voltmeter at this test point, it is effectively in parallel to an internal 10-ohm resistor or the Rs resistor.
Setting your voltmeter / multi-tester to the 1-volt range, if the voltage reading across this point is 500-millivolts or ½ volt, you can use ohms law to compute for the bias current of the particular tube you are measuring – i.e. current = voltage / resistance. Which at 500-millivolts / 10-ohms = 50mA or 50-milliamperes of standing current or bias current. Using this data, you can now compute the EL34 tube’s power dissipation in the amp you are testing. Using Ohm’s law formula to obtain power P=IV or P = 50mA multiplied by 440 volts = 23 watts, which will be the power dissipation of the EL34 tube as used in the particular amplifier design you are measuring. Though the voltage of the H.T. and the resistance value of the Rs resistor could deviate by as much as 10% during normal use.
From a design standpoint, the EL34 tube / valve and its derivatives – like the 6L6, KT77, KT88, 5881, 6550, 6CA7 tubes – were rated by their original manufacturers during the “Golden Age of Stereo” for a maximum anode dissipation of 25 watts and exceeding this rating will drastically shorten tube / valve life. This is so because the excess heat generated by exceeding the tube’s anode dissipation will cause the anode to release what is known as occluded gas, which damages the delicate cathode coating reducing electron emission. Some types of EL34 tubes / valves – especially ones manufactured in Eastern Block countries and China during the 1980s – may also have a low emission to start with and cranking up the quiescent bias current / standing current could cause the tube / valve to saturate on peaks / high-level signals, causing distortion.
Many veteran tube / valve amplifier designers suggest that if you are after extended output tube life, you shouldn’t run EL34-type tubes at over 20 watts of total anode dissipation to lessen the heat generated inside the tube / valve. Unfortunately, cranking up the bias current on these types of tubes usually results in an “improvement” of their high frequency response – i.e. a subjectively much louder high-frequency sound output. Which can be addictive when it comes to tube amps because of their really sweet and grain-free presentation of high-frequency audio information. Some are even known to crank up the quiescent bias currents of the tubes of their EL34s up to 85mA, making the tubes less likely to last more than eight months when use at an average of eight hours a week.
If you want to make the high-frequency response of your tube-based electric guitar amp “seem” louder, do what Queensrÿche does during the late 1980s. Replace the 12-inch Celestion speakers of your Marshall cabs with JBLs. Or if you can afford them 15-inch Leslie-derived organ speakers equipped with a whizzer cone similar to the one used by Jimi Hendrix when he recorded Little Wing in the studio back in 1967.
For those with a more thorough knowledge in tube / valve-based electronics, another method of increasing the high-frequency output of your tube-based electric guitar amplifier is to modify the preamplifier section. The majority of tube-based guitar amps being sold today still use the “conventional” 12AX7-based double-triode phase splitters in their preamplifier sections. The problem with the conventional double-triode phase-splitter is it’s high input capacitance caused by the Miller Effect. This causes high-frequency loading on the input (12AX7-based?) tube and reduces bandwidth, making it very difficult to use appreciable amounts of negative feedback - especially with 6L6 Beam Power Tetrode and EL34 Pentode output tube designs – without instability due to the phase shifts incurred. By the way, negative feedback is a necessity when extracting the maximum output power obtainable of relatively “modern” output power tubes like the 6L6 and the EL34.
Low noise R.F. pentode preamplifier tubes can be used as a better phase splitter in the preamplifier section of tube-based electric guitar amps because a pentode has a very low input capacitance and high gain due to the shielding effect of the screen grid. This means that the capacitance loading on the input tube (12AX7) is greatly reduced, increasing bandwidth and decreasing troublesome phase shifts.
Or if you want the ability to experiment lowering the negative feedback of your electric guitar amp or operating the output power section in triode mode without your amplifier breaking into spurious oscillation. Which could destroy tweeters when you used your tube-based guitar amp as an ad hoc hi-fi tube amp, then use beefier preamplifier tubes like the 5687 tube. The 5687 tube can dissipate 4 watts, it’s dead linear, needs less drive current, and has a low output impedance. Making it able to be used as a driver stage of an inter-stage transformer (Does this remind you of the AN214 driving the inter-stage transformer of an MJ2955-based transformer-coupled booster amp?). If you go with this redesign route, the output tubes of your guitar amp could be configured in self-biased or auto bias mode due to the secondary winding of the driver / inter-stage transformer as opposed to their de rigueur fixed bias configuration.
Auto bias has the advantage of providing automatic compensation of tube variability characteristics, so tube matching and individual bias adjustment will no longer be necessary. Though matched pairs of tubes are still desirable. Auto bias gives that sweet, easy sound tubes possess. Fixed bias gives more power, but a harder sound. In my experience, output tubes of auto-bias configured tube amplifiers tend to last forever. My neighbor’s 300B-based auto-bias amp still uses tubes that he purchased back in 1996 without any degradation in sound quality.
Another way of retaining the de rigueur double-triode preamplifier – i.e. 12AX7 tube-based preamplifier – of your guitar amp is by selecting an output tube designed with a higher mu or a high mu version. I have tried this in the past and it does work but it needs power supply / H.T. circuit modification of your guitar amp. The advantage of this route is that high-mu version of your typical output power tube – like the EL34 and 6L6 – are easier to drive, thus retaining the 12AX7 pre-amp tubes. The caveats include complete redesign of the power supply since high-mu tubes require higher supply voltages than the 450 volts DC needed by your typical output power tube / valve. Some of them needs the power supply / H.T. voltage to be raised to 1,500 volts DC in order to enjoy the maximum benefits of high-mu power tubes. Which can be a problem since power supply capacitors capable of handling 1,500 volts DC are somewhat rare, plus the output transformer needs to be changed to a type that can handle such voltage or your loudspeaker will be turned into a dazzling pyrotechnics display.
Though if you change the choke / inductor filtering the 12AX7 pre-amp tubes to one with a higher inductance – therefore higher DC resistance to lower the incoming voltage supplying the pre-amp tubes, the 12AX7 tubes will be fed with a highly-filtered H.T. DC voltage whose hum is now vanishingly low. Another caveat of this design route is that the output impedance of your guitar amp will now be higher than before – i.e. reduced damping factor – which your amplifiers tonality will be readily be affected by a loudspeaker with a widely-varying impedance curve across the audio band. Although guitar amplifiers that uses minimal amounts of negative feedback and high output impedance are known for their excellent musical performance, so you could probably design an electric guitar amplifier that could double as an excellent sounding domestic hi-fi audio amplifier using this route.
Tuesday, July 21, 2009
The Flat Earth Ideology
Superseded during the 1990s owing to the increasing popularity of vintage low-powered tube amps and very sensitive loudspeakers, is the Flat Earth ideology a vital part of audiophile history?
By: Ringo Bones
Back in the middle of the 1980s, a prominent audiophile sect staunchly believes that the only boxes – i.e. loudspeakers – to have at the end of a righteous audio system should have the word "Linn" written at the back. This somewhat “extremist” hi-fi ideology was aided by enthusiastic hi-fi dealers of the period who are also audiophiles. Not to mention a certain since-defunct periodical / hi-fi magazine called The Flat Response. Thus allowing the hi-fi maker Linn to harbor the ideology that the first priority of a loudspeaker should be the way it played rhythms and the current long-standing global audiophile community’s perception of what is the British Sound was born. Though a Thomas Dolby song from the period titled “Flat Earth” is often played through these systems, reinforcing the need of spot-on rhythm and timing when playing eighties-era synthesizer-based music, but countless others probably use theirs to unravel the rhythmic complexity of Iron Maiden’s The Number of the Beast album.
The most uncompromising embodiment of this hi-fi ideology was the Kan, a tiny box manufactured by Linn. Equipped with treble and mid drivers similar to that used in Linn’s flagship brand the behemoth-sized Isobarik loudspeakers. Back around the middle of the 1980s, the Linn Kans was capable very captivating performance. These loudspeakers sounded extremely fast and extremely tight, with an “uncanny” ability to disappear into their own soundstage. Linn’s bigger – and more efficient – loudspeaker models never convincingly displayed the ability of the smaller Kan’s hi-fi slight-of-hand.
The Kan also has a profoundly fussy approach to matching ancillary components, ironically the little speaker’s “soul-mate” is an equally fussy solid-state power amplifier made by Naim called the NAIT that produced only 30 watts into an eight-ohm load. But during that era in the 1980s, the little Kan – if you wanted more than a squeak from these relatively inefficient speakers - was often paired up to a large muscular solid-state full complementary direct coupled amplifier with a power output of around 80 to 100 watts into an eight-ohm load. The hi-fi community’s renewed obsession with flea-powered tube / valve amps and Maytag washing machine-sized horn loudspeakers were still a decade away.
On the front-end side of things, Flat Earth systems didn’t like inferior source components. CD players circa 1983 was excruciatingly painful-sounding when played through the Kans, plus the early CD’s still suboptimally designed output filters produced so much rhythmic and timing anomalies that it negates the idea of having a Flat Earth system in the first place. Meaning in those days, it was Linn’s pre-braced plinth Valhalla LP12 with LVX+ and Basik cartridge, a Roksan Xerxes, or nothing.
The “dark side” of the Flat Earth ideology is that it made every audiophile – especially in merry old England – harbor the belief that tube / valve amps (especially low-powered ones) from the Golden Age of Stereo were deemed obsolete during the go-go eighties. The Flat Response hi-fi magazine didn’t helped matters either because reviewers of the Flat Earth disposition showed scant knowledge and interest when it comes to the science – and art – of loudspeaker matching. Using quintessentially 1980s era hard to drive loudspeakers with which most tube amplifiers played through them had to struggle. Maybe it was the sound of Leak Stereo 20s wheezing and groaning under the load of a pair of Linn Saras that many Flat Earth-leaning audiophiles conclude that tube amplifiers are now – in the mid 1980s – obsolete. Thus benefiting hordes of East Asian vintage audio enthusiasts.
By: Ringo Bones
Back in the middle of the 1980s, a prominent audiophile sect staunchly believes that the only boxes – i.e. loudspeakers – to have at the end of a righteous audio system should have the word "Linn" written at the back. This somewhat “extremist” hi-fi ideology was aided by enthusiastic hi-fi dealers of the period who are also audiophiles. Not to mention a certain since-defunct periodical / hi-fi magazine called The Flat Response. Thus allowing the hi-fi maker Linn to harbor the ideology that the first priority of a loudspeaker should be the way it played rhythms and the current long-standing global audiophile community’s perception of what is the British Sound was born. Though a Thomas Dolby song from the period titled “Flat Earth” is often played through these systems, reinforcing the need of spot-on rhythm and timing when playing eighties-era synthesizer-based music, but countless others probably use theirs to unravel the rhythmic complexity of Iron Maiden’s The Number of the Beast album.
The most uncompromising embodiment of this hi-fi ideology was the Kan, a tiny box manufactured by Linn. Equipped with treble and mid drivers similar to that used in Linn’s flagship brand the behemoth-sized Isobarik loudspeakers. Back around the middle of the 1980s, the Linn Kans was capable very captivating performance. These loudspeakers sounded extremely fast and extremely tight, with an “uncanny” ability to disappear into their own soundstage. Linn’s bigger – and more efficient – loudspeaker models never convincingly displayed the ability of the smaller Kan’s hi-fi slight-of-hand.
The Kan also has a profoundly fussy approach to matching ancillary components, ironically the little speaker’s “soul-mate” is an equally fussy solid-state power amplifier made by Naim called the NAIT that produced only 30 watts into an eight-ohm load. But during that era in the 1980s, the little Kan – if you wanted more than a squeak from these relatively inefficient speakers - was often paired up to a large muscular solid-state full complementary direct coupled amplifier with a power output of around 80 to 100 watts into an eight-ohm load. The hi-fi community’s renewed obsession with flea-powered tube / valve amps and Maytag washing machine-sized horn loudspeakers were still a decade away.
On the front-end side of things, Flat Earth systems didn’t like inferior source components. CD players circa 1983 was excruciatingly painful-sounding when played through the Kans, plus the early CD’s still suboptimally designed output filters produced so much rhythmic and timing anomalies that it negates the idea of having a Flat Earth system in the first place. Meaning in those days, it was Linn’s pre-braced plinth Valhalla LP12 with LVX+ and Basik cartridge, a Roksan Xerxes, or nothing.
The “dark side” of the Flat Earth ideology is that it made every audiophile – especially in merry old England – harbor the belief that tube / valve amps (especially low-powered ones) from the Golden Age of Stereo were deemed obsolete during the go-go eighties. The Flat Response hi-fi magazine didn’t helped matters either because reviewers of the Flat Earth disposition showed scant knowledge and interest when it comes to the science – and art – of loudspeaker matching. Using quintessentially 1980s era hard to drive loudspeakers with which most tube amplifiers played through them had to struggle. Maybe it was the sound of Leak Stereo 20s wheezing and groaning under the load of a pair of Linn Saras that many Flat Earth-leaning audiophiles conclude that tube amplifiers are now – in the mid 1980s – obsolete. Thus benefiting hordes of East Asian vintage audio enthusiasts.
Thursday, July 9, 2009
Vintage Audio Gear: More Hype Than Hi-Fi?
Given that the laws of progress dictates that the latest technology is surely better than yesterday’s, are some audiophile’s obsession with old / vintage audio gear beyond common sense?
By: Ringo Bones
Since the 1970s, people who buy aggressively marketed 500 dollar audio gear then listen to them with 10,000 dollar audio analyzers had been ridiculing us audiophiles who buy reasonably-priced audio gear of several years vintage then listen to it with our own two ears. Sadly, this vulgar act of “bullying” resulted in a minor – albeit tragic – disaster of vintage audio gear being diverted into the Far Eastern markets. This “disaster” affected mostly American and West European audiophiles and it took twenty years – more or less – to mitigate.
It is safe to point the blame at mainstream consumer electronic manufacturers who probably discovered during the 1970s that audio gear that measures perfectly on the test bench is far cheaper to manufacture than a really good sounding one that measures slightly worse. Thus, the mainstream consumer electronic manufacturers began aggressively marketing their latest audio gear – especially audio amplifiers – based on specs like total harmonic distortion, power output, etc. instead of ultimate sound quality and / or musicality.
During the 1980s vintage audio gear – especially vacuum tube-based audio amplifiers – began to skyrocket in price, especially in America where vintage audio gear manufactured during the Golden Age of Stereo began to appear in garage sales and weekend swap meets. It is not just trusty tube-based receivers, like the venerable Fisher 500-C that gained sacred cow status. Not to mention McIntosh tube-based audio gear. Even vacuum tubes, especially new old stock (NOS) versions of 12AX7 pre-amp tubes, Western Electric 300B tubes, KT-66, KT-88, EL-34 output tubes. And even the 7591A output tubes used in the Fisher 500-C receiver began to skyrocket in price soon after because American electronic manufacturers find that it is not economically viable - during the Reagan Administration - to manufacture vacuum tubes in quantities that would only cater audiophiles and electric guitar players. Exotic capacitors, like Sprague Vitamin Q paper-in-oil capacitors, also followed suit into cult status. Add to that the inherent unreliability of tubes manufactured in t People's Republic of China during the 1980s when compared to NOS American types - thus producing the Perfect Storm of "criminal pricing" of vintage audio gear from the Golden Age of Stereo.
Sadly, your typical Far Eastern vintage audio enthusiast had been busy swallowing up these under-appreciated aspects of Americana – if you’re willing to believe the hype in the hi-fi press anyway. Not just American-made vintage audio gear, even tube-based ham radios and electronic test equipment had already become hot collector items in Japan and other affluent parts of the Orient. Maybe there are plans in Japan for a musical based on the movie Frequency. You know, that move where James Caviezel’s character managed to contact his father played by Dennis Quaid using a tube-based ham radio 30 years in the past due to a freak solar storm.
But in reality, not everyone in Japan is a vintage audio enthusiast. Only those who have the time, money, and living space to indulge – and enjoy – choose vintage audio gear as their hobby. Because a typical pre-global credit crunch salaried employee in Japan who earns a middling income usually lives in a cramped 425 square-foot apartment. Thus very unlikely to invest – and indulge – in a vintage stereo system that costs more that a third of his annual salary and takes up most – if not all – of the space in his living quarters. So PX25 tube amps and 1950s-era Tannoy horn loaded speakers are out of the question.
The good news is that from a financial perspective, indulgence in vintage audio gear is no longer comparable in cost to a two-week working vacation in the International Space Station like it did during the 1980s – it is much, much cheaper now. Not to mention the availability of solid-state amps that sound just as good as tube-based amps since the mid 1990s – well, good enough if you consider the retail price anyway. But the primary reason why vintage audio gear had become a way less expensive hobby during the 21st Century is that some well-meaning folks and manufacturing firms have restarted making vintage audio gear and their associated parts – not to mention better-sounding audiophile-grade compatible replacement equivalent parts – at very reasonable prices. Like the Electro-Harmonix version of the 7591A output tubes by Sovtek of Russia so that everyone can restore their Fisher 500-C receiver without having to spend family car prices.
Looks like 2009 is going to be a very good time for the vintage audio enthusiasts. Unless some speculative swine starts to create hype over discontinued and rare solid-state components, like the AN214 IC amplifier, or the XR2206 Monolithic Function Generator IC and its related kit. And the bad news is that it has already begun because since 2001, the AN214 IC – if you can still manage to find one – was being sold at prices above what a Telefunken 12AX7 pre-amp tube used to sell. Maybe you should hold on to that Sansui AU-a707DR integrated amplifier before selling it to this Sunday’s garage sale.
By: Ringo Bones
Since the 1970s, people who buy aggressively marketed 500 dollar audio gear then listen to them with 10,000 dollar audio analyzers had been ridiculing us audiophiles who buy reasonably-priced audio gear of several years vintage then listen to it with our own two ears. Sadly, this vulgar act of “bullying” resulted in a minor – albeit tragic – disaster of vintage audio gear being diverted into the Far Eastern markets. This “disaster” affected mostly American and West European audiophiles and it took twenty years – more or less – to mitigate.
It is safe to point the blame at mainstream consumer electronic manufacturers who probably discovered during the 1970s that audio gear that measures perfectly on the test bench is far cheaper to manufacture than a really good sounding one that measures slightly worse. Thus, the mainstream consumer electronic manufacturers began aggressively marketing their latest audio gear – especially audio amplifiers – based on specs like total harmonic distortion, power output, etc. instead of ultimate sound quality and / or musicality.
During the 1980s vintage audio gear – especially vacuum tube-based audio amplifiers – began to skyrocket in price, especially in America where vintage audio gear manufactured during the Golden Age of Stereo began to appear in garage sales and weekend swap meets. It is not just trusty tube-based receivers, like the venerable Fisher 500-C that gained sacred cow status. Not to mention McIntosh tube-based audio gear. Even vacuum tubes, especially new old stock (NOS) versions of 12AX7 pre-amp tubes, Western Electric 300B tubes, KT-66, KT-88, EL-34 output tubes. And even the 7591A output tubes used in the Fisher 500-C receiver began to skyrocket in price soon after because American electronic manufacturers find that it is not economically viable - during the Reagan Administration - to manufacture vacuum tubes in quantities that would only cater audiophiles and electric guitar players. Exotic capacitors, like Sprague Vitamin Q paper-in-oil capacitors, also followed suit into cult status. Add to that the inherent unreliability of tubes manufactured in t People's Republic of China during the 1980s when compared to NOS American types - thus producing the Perfect Storm of "criminal pricing" of vintage audio gear from the Golden Age of Stereo.
Sadly, your typical Far Eastern vintage audio enthusiast had been busy swallowing up these under-appreciated aspects of Americana – if you’re willing to believe the hype in the hi-fi press anyway. Not just American-made vintage audio gear, even tube-based ham radios and electronic test equipment had already become hot collector items in Japan and other affluent parts of the Orient. Maybe there are plans in Japan for a musical based on the movie Frequency. You know, that move where James Caviezel’s character managed to contact his father played by Dennis Quaid using a tube-based ham radio 30 years in the past due to a freak solar storm.
But in reality, not everyone in Japan is a vintage audio enthusiast. Only those who have the time, money, and living space to indulge – and enjoy – choose vintage audio gear as their hobby. Because a typical pre-global credit crunch salaried employee in Japan who earns a middling income usually lives in a cramped 425 square-foot apartment. Thus very unlikely to invest – and indulge – in a vintage stereo system that costs more that a third of his annual salary and takes up most – if not all – of the space in his living quarters. So PX25 tube amps and 1950s-era Tannoy horn loaded speakers are out of the question.
The good news is that from a financial perspective, indulgence in vintage audio gear is no longer comparable in cost to a two-week working vacation in the International Space Station like it did during the 1980s – it is much, much cheaper now. Not to mention the availability of solid-state amps that sound just as good as tube-based amps since the mid 1990s – well, good enough if you consider the retail price anyway. But the primary reason why vintage audio gear had become a way less expensive hobby during the 21st Century is that some well-meaning folks and manufacturing firms have restarted making vintage audio gear and their associated parts – not to mention better-sounding audiophile-grade compatible replacement equivalent parts – at very reasonable prices. Like the Electro-Harmonix version of the 7591A output tubes by Sovtek of Russia so that everyone can restore their Fisher 500-C receiver without having to spend family car prices.
Looks like 2009 is going to be a very good time for the vintage audio enthusiasts. Unless some speculative swine starts to create hype over discontinued and rare solid-state components, like the AN214 IC amplifier, or the XR2206 Monolithic Function Generator IC and its related kit. And the bad news is that it has already begun because since 2001, the AN214 IC – if you can still manage to find one – was being sold at prices above what a Telefunken 12AX7 pre-amp tube used to sell. Maybe you should hold on to that Sansui AU-a707DR integrated amplifier before selling it to this Sunday’s garage sale.
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