Tuesday, December 5, 2017

Does Power Supply Electrolytic Capacitors Have a Finite Lifespan?

They may last forever in so-called “textbook conditions”, but do capacitors used in real-world situations really have a finite lifespan?

By: Ringo Bones

The topic of capacitor mortality entered the conversation radar of my audiobuddies late last year when Sunfire founder Bob Carver voiced his concern after many of his Tracking Downconverter / PWM power supply equipped power amps “flooded” the online second hand market. And given a majority of these are from the mid to late 1990s and on average are 20 years old – or a bit older, Carver cautions the potential buyer to first service and / or troubleshoot these amps, especially check the power supply capacitors since given the pulse-width-modulation type power supply nature of these amps, the main electrolytic capacitors have a theoretically much shorter lifespan than power amps using conventional linear power supplies. Another power amp that’s very popular in the online second-hand market is the Musical Fidelity A1, which requires a careful main power supply capacitor examination since it runs hot at 50 to 65 degrees Celsius and the inside where the capacitor lies could get much hotter.

The power amplifier’s overall layout and operational temperature plays a very important part on the “mortality” of its main power supply filter capacitors since the leakage current of insulators and consequently all capacitor types, increases with temperature due to Arrhenius’s Law. The power dissipated in a capacitor subject to alternating current stress or ripple is a product of effective series resistance and RMS current. The effective series resistance and impedance of capacitors are both dependent on which frequency they operate and hence must be ascertained at the relevant frequencies. Assuming sinusoidal waveforms – as in a typical linear power supply – RMS current can be easily determined. With other waveforms – as in those Bob Carver power amplifier designs equipped with Tracking Downconverter / pulse width modulation type power supplies, the only accurate method requires the use of the Fourier analysis of the capacitor voltage waveform to determine the frequency components and hence permit calculation of the current for each harmonic involved. For those preferring to avoid the complications of Fourier analysis, a workable rule-of-thumb is to check the temperature rise of the capacitor case. If less than 5 degrees Celsius above the ambient temperature of inside the power amp’s casing of say 55 degrees Celsius maximum, leave well alone; if greater (as in hotter) – investigate immediately.

The normal failure mode of aluminum electrolytic capacitors is gradual parametric degradation after years of operation. But I’ve noticed to cool running power amp designs whose insides are only 3 to 5 degrees Celsius higher than the ambient room temperature, the main power supply electrolytic filter capacitors seem to measure within its parameters after 25 years of regular operation –i.e. 4 to 5 hours a day being played; Whereas for other capacitor types, normal failure mode is by short circuit. This parametric degradation results from the finite volume of electrolyte and the consumption of available oxygen.

The leakage current of normal capacitor operation consumes minute quantities of oxygen from the electrolyte, releasing a corresponding amount of hydrogen which is either reabsorbed in the electrolyte or escapes to the atmosphere. Excess quantities of gas result if: 1) the said capacitor is subjected to DC voltages way beyond its rated capacity. 2) The capacitor used in power supply filtering is subjected to alternating current for several minutes perhaps due to a short circuited rectifier diode and the power supply fuse not blowing. 3) The DC bias is externally reversed by circuit action and / or alternatively internal reverse DC bias due to excessive ripple or discharge currents. 4) Series or parallel connected capacitor banks not having suitable voltage or current sharing provisions.

When considering capacitor failures, it is essential to remember that all electrolytic capacitors comprise of two polarized capacitors back-to-back connected in series. This is implicit in the construction methods, both for polar and non-polar devices, which differ only in effective working voltage of the two capacitors. So if that Rubycon Black Gate electrolytic capacitor you installed in your power amp back in 1988 sill makes your low-power solid state design sound as if it is a single-ended triode tube amp, then it consider yourself lucky and keep it in place.  

Monday, May 16, 2016

Can Graphene Semiconductors Make Future Solid State Audio Power Amps Sound Like Vacuum Tube Amps?

Given that electrons can travel more than 100 times faster in graphene than in copper, will the upcoming graphene based semiconductors make solid state amps sound like vacuum tube amps? 

By: Ringo Bones 

Though they’ve been identified as far back as 1947 as being 207 times stronger than steel and make electrons travel 100 times faster through them than through copper wires, the carbon allotrope graphene was only manufactured / synthesized in significant amounts back in the 1970s by Manchester University physicists Prof. Andrei Geim and Konstantin Novoselov which made them the recipient of the 2010 Nobel Physics Prize. But more recently, various methods to manufacture graphene in higher volumes and far lower costs than before have recently made them economically viable enough for semiconductor applications. Given faster electron flow / electron mobility and high tensile strength, could upcoming graphene semiconductors someday make solid state hi-fi amplifiers sound like their famed vacuum tube counterparts? 

During the 1990s many research articles were written about why hi-fi solid state power amplifiers sound different from their thermionic vacuum tube counterparts. But during the latter half of the 1990s, solid state integrated amplifiers that used “high electron mobility” semiconductors – i.e. solid state devices that used indium antimonide that are "blocked out" to protect the secret of their designs whose electron flow is up to 50 times that of copper wire and or power transistors enclosed in nonmagnetic packaging like TO-3 packaged 2N3055 NPN transistors in brass as opposed to the bog standard magnetic stainless steel. Even though these amps tend to be overpriced – average price between 3,000 to 5,000 US dollars each were their equivalent circuit counterparts using bog standard output devices tent to sell on average one-tenth of their price. Many audio engineers and hi-fi enthusiasts have wondered whether the difference in sound / timbre of solid state power amps and vacuum tube power amps is largely due to the speed of electrons travel through their output devices. 

Electrons and electromagnetic waves propagate in vacuum at a maximum speed of 299, 792, 458 meters per second – usually rounded to 3-million meters per second or more famously known as 186,000 miles per second or 670-million miles per hour. A 12-gauge copper wire carrying a 10-ampere DC current, the speed of the electrons traveling through it is about 80 centimeters per hour – or about 0.0002 meters per second. A current traveling through a silicon-based semiconductor is about the same. While a velocity of an electron by the time it reaches the anode after being accelerated by the anode’s field is truly mind boggling by comparison. For example a vacuum tube with a fairly typical anode voltage of 450-volt DC, the electrons will hit the anode at approximately 12-million meters per second or 28 million miles per hour.  

Remember those “overpriced” integrated amplifiers that use exotic high electron mobility solid state devices that sound like vacuum tube power amps? The average electron mobility rating of the active output devices that these amp use are 50 times that of typical silicon based output devices. Is electron mobility / electron speed the secret to better subjective sound quality? Well, electron flow in a typical indium antimonide semiconductor is around 0.01 meters per second and on graphene based semiconductors is 0.02 meters per second – quite a lot faster than a silicon semiconductor’s 0.0002 meters per second. Will high electron mobility spell improved subjective sound quality for upcoming graphene based solid state high fidelity audio amplifiers?

Sunday, April 10, 2016

Are Physical Digital Formats Better Than Digital Downloads?

From a sound quality perspective – are digitally downloaded music stored in solid state memory sounds inferior in comparison to their physical digital counterparts? 

By: Ringo Bones 

Ever since legal digital music downloads became a commercially viable reality that benefited both artists and record labels, it has been touted by environmentally concerned individuals as a “green” way of selling music around the world because this means that there are no shipping of CDs and other physical formats around the world that produce significant amounts of carbon dioxide emissions. Musical distribution carbon footprint would be limited to the power used by servers and PCs or other devices used to download the music and this could be much lower if those devices are powered by renewably-generated electricity. From an electronic engineering perspective, digital music stored in solid state memory has “supposedly” eliminated the problems of digital jitter in comparison to 120-centimeter CD or DVD discs played in a transport. But why is it that an increasing number of audiophiles have noticed that downloaded music, more often than not, sounded inferior in comparison to its physical counterparts?

Ever since the popularity of universal players that are able to play any 12-centimeter disc – whether it be 16-bit CDs, DVD-video, DVD-audio and Super Audio CDs – and digitally downloaded music via a USB slot, many budget conscious audiophiles, including me, had noticed that digitally downloaded music, even high resolution ones that are in FLAC (Free Lossless Audio Codec) format tend to sound inferior to their physical format. In my own experience, using a 150 US dollar Oppo universal player, physical Redbook 16-bit 44.1-KHz sampled CDs tend to sound better than their downloaded 24-bit 192-KHz FLAC encoded counterparts. The most common recordings that are usually available in both that can be compared side-by-side using a universal player are Miles Davis’ Kind of Blue album and Martin Taylor’s Spirit of Django album. 

To my ears, it seems as if the downloaded versions sounds as if it has the sound quality of a typical 100 US dollar CD player while the physical versions sounds as if it has the sound quality of a typical 500 US dollar CD player. And to Stereophile magazine leaders, most downloaded music played on universal players priced between 150 to 500 US dollars via its USB slot has a digital sound that Stereophile contributor Michael Fremer used to describe back in the 1990s as “everything gets flattened out – including dynamics. Given that solid state storage devices supposedly doesn’t have the digital jitter inherent in CD / DVD / SACD drives, why is it that digitally downloaded music – even hi-rez ones – sound inferior to their physical counterparts?  By the way, digitally downloaded music only started to sound as good as of better than their physical formats only after I’ve burned them into their requisite 12-centimeter recordable CD or DVD discs using a PC with Windows Media Player that can handle FLAC encoded music data.  

Monday, March 7, 2016

Amazing Synchronicities In Hi-Fi and AV?

Some of the other hi-fi and audio-video enthusiasts out there had been doing this for more than 20 years, but have you ever noticed the growing number of “amazing synchronicities”?

By: Ringo Bones 

About 20 or so years ago when serious hi-fi enthusiasts who are “mere mortals” can finally afford DVD players that can seamlessly hook-up into their hi-fi rigs. They began experimenting on what they’ve found out on the internet that if you start Pink Floyd’s Dark Side of the Moon album at just the right moment while watching The Wizard of Oz, amazing synchronicities occur between what’s on the screen and what’s heard in the lyrics and music. I and countless others who have tried it during the past 20 years swear that it works. Since then, this specific hi-fi phenomenon has since been dubbed “Amazing Synchronicities” and has ever since fostered various websites and discussion posts on the internet since the 21st Century began. When it comes to Pink Floyd’s Dark Side of the Moon album and The Wizard of Oz – “who knows witch is which….” Indeed. But did you know that there are other “startling coincidences” and “amazing synchronicities” that every hi-fi and AV enthusiasts can test out on their own systems? 

Pink Floyd’s Wish You Were Here and Blade Runner also eerily synchs up like a music video. And also at the end of Stanley Kubrick’s science fiction classic 2001: A Space Odyssey where a 22-minute sequence titled “Jupiter and Beyond the Infinite” eerily synchs up with Pink Floyd’s Echoes, which is also 22-minutes long. Although Kubrick’s original score in “Jupiter” is already as good as it is. My stumbled upon favorite on You Tube was a video reenactment of the September 16, 2007 Nisour Square Massacre – that notorious Blackwater Security Consulting’s unwarranted shooting of unarmed Iraqi civilians where Tori Amos’ Precious Things (track number 5 of her Little Earthquakes album) eerily syncs in with the carnage - although this piece has been since taken out from You Tube. Maybe the maker didn't pay Tori Amos royalties and got a cease and desist order. And I bet every hi-fi enthusiasts the world over had tried probably almost anything since 1995 after discovering their first “amazing synchronicities” between Pink Floyd’s Dark Side of the Moon album and The Wizard of Oz movie. 

Saturday, February 13, 2016

Is Your Audio System Cat-Friendly?

While early high fidelity audio systems got notoriety for “scaring away the horses” – is your current audio set-up cat-friendly?

By: Ringo Bones 

Maybe we should blame cellist David Teie for this given that his Kickstarter funded research into feline-centric / species-appropriate music that recently got scientific verification by a recent independent study conducted by researchers at the University of Wisconsin and published in Applied Animal Behavior. Also, Teie’s Music for Cats compositions recently got scores of positive testimonials by early purchasers who tested Teie’s cat music recordings on their own cats noting that it actually had a relaxing effect on their own pets. 

Cello player David Teie comes from a long line of musicians, composers and professional instrumentalists. Since 2014, he has been the conductor and music director of Washington D.C.’s premier chamber orchestra – the Eclipse Chamber Orchestra – and currently serves on the faculty at the University of Maryland’s School of Music. Teie’s career has spanned performing as a soloist with the National Symphony Orchestra under Russian maestro Mstislav Rostropovich. And also as the acting principal cellist of the San Francisco Symphony where Teie performed as cellist on Metallica’s 1999 album S&M. His research has been published in the Royal Society Biology Letters and in Evolution of Emotional Communication. His invention of species-specific music was described by the New York Times as the number one idea of 2009. 

According to cellist David Teie, cats were our first choice because they’re widely kept as pets which allowed us to easily share music with them. Given that cats can hear audio frequencies way above the human hearing frequency limit of 20,000-Hz, can cats even appreciate those upper octaves of Teie’s music given that most entry-level audio systems have trouble playing at significant volume – never mind proper phase linearity – of audio signals above 20,000-Hz? 

With the relatively wide availability and relative affordability of audio components and recordings capable of producing cleanly audio signals above 20,000-Hz – i.e. 24-Bit 192-KHz sampled PCM DVD Audio files and Super Audio CD recordings that can produce notes above 100,000-Hz and some moving coil cartridges like the Dynavector 17D2MkII Karat Diamond whose shorter 1.7-mm diamond cantilever allow it to have a high-frequency extension above 100,000-Hz and diamond coated tweeters that can cleanly play 100,000 Hz or higher audio frequencies – then it is now relatively easy to upgrade your audio system that can produce sounds that even cats, dogs and even bats can clearly hear. 

Maybe it was due to the fact that he hanged out with Metallica for a relatively long time during rehearsals in comparison to us mere fans back in 1999 or whether he is already a Metallica fan back when bassist Cliff Burton was still alive that got me wondering how much Metallica was an influence to cellist David Teie upon hearing of Cozmo’s Air – one of the tracks of his Music for Cats – that it reminded me of the ambient into of Metallica’s Damage, Inc. – the last track on the Master of Puppets album. Well, at least Teie managed to make his “cat music” also interesting to hear for us human music lovers which will probably give Pet Sounds a whole new meaning to audiophiles around the world. 

Monday, February 1, 2016

Transmission Line Loudspeakers: The Ultimate Domestic Hi-Fi Loudspeakers?

Given its ability to produce unbelievable amounts of bass for its size, are transmission line loudspeakers qualify as the ultimate domestic hi-fi loudspeakers?

By: Ringo Bones

As of late, there has been discussion on how come hi-fi audio designer Arthur Radford’s electronics – especially his EL34 based audio power amplifiers like the Radford STA25 - get more recognition in comparison to his transmission line loudspeakers which despite being manufactured 50 or so years ago can still manage to hold its own in a side-by-side comparison to more recently manufactured hi-fi loudspeakers. Arthur Radford did a lot of work, both theoretical and practical, on transmission line loudspeaker design during the 1960s.The Radford Studio 90 which was also sold in the U.S. in kit form during the late 1960s as the Audionics TL90 – a ¼ wavelength 3-way transmission line loudspeaker equipped with Radford sourced drivers and crossover circuit. The Radford Studio 90 was the first commercially manufactured hi-fi transmission line loudspeaker based on A.R. Bailey’s papers and there are even larger models based on the same design. Even though they were a bit pricey when they first entered the market, enough of them were sold in the United States to establish a “cult following” of this legendary loudspeakers. Despite their excellent subjective sound quality, why are transmission line loudspeakers relatively rare in comparison to competing designs? But first, here’s an introduction on the theoretical and practical principles of transmission line loudspeakers. 

Then and now, designers of closed-box / acoustic suspension and vented / bass reflex loudspeaker systems have long been able to make heavy use of computers, while transmission line systems had been designed by cut-and-try methods. Transmission line loudspeaker systems are more complicated to design because of their inherent distributed-parameter nature. By way of comparison, sealed / acoustic suspension and vented / bass reflex loudspeaker systems can be treated as a much simpler, lumped-parameter acoustic systems. Also, there is still a dearth of research literature regarding transmission line loudspeaker design to guide the prospective designer. But to those adventurous enough, they should check out Quick & Easy Transmission Line Speaker Design by Larry D. Sharp and those “white papers” published online by John Wright of TDL. 

Transmission line loudspeakers are known for their deep, powerful bass and the way they grip a room, filling it with a full scale performance. But they have their downsides too, notably the difficulty of tuning the line, which appears to be the blackest of arts in the audio engineering world. A practical transmission line has two main effects that are advantageous to loudspeaker design. Firstly, the sound venting from the end of a quarter-wavelength transmission line is 90-degrees out of phase with the signal from the back of the cone which drives the line, which itself is 180-degrees out of phase with the front radiation. This ensures that sound radiation at lower frequencies is progressively moving into phase and it will add, rather than subtract, to the forward low frequency response. Also a practical transmission line loudspeaker is lined with acoustic felt and wool, so that a majority of upper bass and midrange energy is absorbed before it reaches the end of the line and the outside world. Lower frequency bass energy gets through, making low bass apparent. In electrical engineering terms, a transmission line port is a low pass filter with a 270-degrees plus phase shift. 

An area where transmission line loudspeakers receive criticism is midrange coloration. To overcome this, various transmission line loudspeaker designers over the years adapted a number of sensible design features. If the transmission line vent length is made exactly ¼-wavelength in length, it tends to act like a tuned pipe which introduces coloration. Making the transmission line slightly shorter, a technique later adapted by John Wright of TDL during the late 1960s, reduces this coloration without adversely affecting bass quality.
In some transmission line loudspeaker designs where the line is folded quickly behind the cone, the strongly reflected sound wave from the cabinet wall can give that “clatter-type” coloration in the midrange. For this reason, in newer transmission line loudspeaker designs, the rear wall of the cabinet is kept as far back as possible and fitted with a generous covering of soft, absorbent carpet felt. 

One great thing about a transmission line loudspeaker is that once the cabinet dimensions have been optimized and fixed, it can be subtly tuned to give the bass quality you want in your listening room just by altering the amount and density of long hair wool in the line. This makes transmission line loudspeakers extremely versatile for home constructors, which combined with their subjective performance explains why they’ve been making a comeback since the 1990s hi-fi boom. 

Another great advantage, or possibly the greatest advantage, of transmission line loudspeakers – and probably why they’ve returned during the 1990s in conjunction with the zero negative feedback single-ended-triode audio amplification Renaissance of the period - is their highly damped impedance curve. Impedance varies little across the entire audio spectrum – especially in the upper bass and lower midrange region in comparison with vented / bass reflex and closed box / acoustic suspension loudspeakers. This makes transmission line loudspeakers much, much easier to drive with zero negative feedback single-ended triode audio amplifiers and other low feedback vacuum tube audio amplifier designs.