The Radford STA Series Of Amplifiers: The Most Modern Of Vintage Hi-Fi Amplifiers?

Despite being a “modern” pentode design, does the Radford STA series of vacuum tube audio amplifiers claim to fame as a great vintage hi-fi amp is its “classic” vacuum tube sound? 

By: Ringo Bones 

When I got seriously into hi-fi during the Clinton Administration, any audio gear older than Chelsea Clinton is already considered “vintage hi-fi”, even back then, whether original or reissue, Radford’s STA series of stereo audio hi-fi amplifiers were already considered vintage classics. When Arthur Hedley Radford established Radford Electronics in 1946 and marketed his first hi-fi amp in 1959, little did he know back then that his very products will soon become very sought-after vintage hi-fi classics that they currently are now?

It was the Series Two amplifiers, soon to change into the Series Three range comprising of two monoblocks – the MA15 and the MA25 plus two stereo versions – the STA15 and STA25 -  and the matching SC22 preamplifier (available for around UK£32 back in 1964-65) that put Radford on the map. Famed for its good sound quality and considered a perfect match for Radford’s STA series of audio amplifiers when it comes to vinyl LP replay, the preamp’s exemplar vinyl LP replay performance was primarily due of its avoidance of the use of steep-cut rumble / subsonic filters. Steep-cut rumble / subsonic filters tend to be disliked by audio purists because the benefits of steep-cut filters in terms of vinyl record warp suppression is often easily offset by audible phase and group-delay distortion they introduced, messing up with the percussive transients of a recorded drum kit. Group-delay distortion is also the primary reason why older CD players suck in comparison to good entry level vinyl record replay equipment. 

The Radford STA15 and STA25 series of audio amplifiers – as well as their monoblock siblings – employ a variation of the classic Philips / Mullard 5-20 circuit with the first stage utilizing a high-gain EF86 RF pentode preamplifier vacuum tube that feeds into a 6U8 (ECF82) dual triode / dual pentode vacuum tube as a phase splitter to drive a pair of EL34 power pentode vacuum tubes in push-pull mode. The output transformers use ultra linear connection. Sound wise, the bass are a bit unruly by solid-state audio amplifier standards but the midrange sound quality could give lesser single-ended triode designs a run for their money.  

If you are asking why the second-hand prices of Radford STA15 and STA25 have skyrocketed way ahead of their Blue-Book inflation adjusted figures can be traced to a crucial point back in hi-fi history. Back in 1975, hi-fi journalist Martin Colloms set up a major blind listening test of 18 hi-fi audio power amplifiers for a long since defunk UK hi-fi magazine called Hi-Fi For Pleasure. Back in 1975, the transistor amplifier (well, the better designed ones, anyway) was already well accepted by audiophiles. Prices of the review samples ranged from US$300 to US$3,000 – about equivalent to US$1,200 to US$12,000 in today’s money. The auditioning sessions were graced by the presence of many hi-fi industry leaders, among them Spencer Hughes of Spendor, Julian Vereker of Naim, Philip Swift of Audiolab, Alan Harris of retailer Audio T., Bob Stuart of Meridian and John Wright of IMF now TDL in UK. 

On the suggestion of Alan Harris – a serious vacuum tube audio amplifier fan – Martin Colloms introduced a ringer to those tests: an “ancient” (over 10 years old) 25-watt per channel vacuum tube audio amplifier, the Radford STA25 Mk. III, worth perhaps US$100 on the used market back in 1975. Colloms used a selection of master tapes as the source. When the results of the blind test were analyzed, the vacuum tube Radford had come on top despite showing the poorest measured performance in comparison to “more modern” solid-state audio amplifier designs. Needless to say, the Radford’s second-hand value soared after the review was published. Based on what we know now, it might be due to the Radford’s use of very small amounts of negative feedback which its design is around less than 20 decibels worth as opposed to a typical solid-state audio amplifier design which needed at least 46 decibels of negative feedback or it will burst into oscillation. 

Due to their recently achieved “cult status” and growing demand from high fidelity audio enthusiasts, a limited run of the Radford STA25 vacuum tube audio amplifiers were released to the market in England back in 1984 to 1985. With the high fidelity vacuum tube audio amplifier revival becoming newsworthy by the early 1980s – and despite of the increasing vacuum tube scarcity in America during the Reagan Administration – all it took was a lot of nagging to get the then semi-retired Arthur Radford to permit his former employee, John Widgery of Woodside Electronics, to oversee the run of 100 individual units of the Radford STA25s. These amplifiers were designated Mk. IVs and painted gloss black with gold trim to distinguish them from the battleship gray originals. Each of these came with a certificate of authenticity signed by Arthur Radford himself. After his death back in November 21, 1993, the 100 lucky owners of the Limited Edition Radford STA25 Mk. IVs saw their treasures appreciate in value in high fidelity audio collector circles. 

The Svetlana 811 Power Triode: The Future Of Single Ended Triode Audio Amplifiers?

Despite the “technology” dating back to 1928, does the 811 power triode vacuum tube represent the “future” of single-ended triode audio amplifiers?

By: Ringo Bones 

 

To those old enough to remember first hand, the second half of the 1990s could be described as “very disconcerting” times for the consumer electronics industry because during the 1995 Winter Consumer Electronics Show, a number of veteran vacuum tube manufacturers led by Western Electric announced that they would be remanufacturing their line of vacuum tubes for the high fidelity audio market. And this was a time almost 50 years after Shockley, Bardeen and Brattain invented the transistor at Bell Labs! 

Forget that single ended triodes are a late 1920s technology, major consumer electronics manufacturers familiar to the general public – i.e. Sony and Bose – has yet to manufacture an affordable and widely  available domestic hi-fi audio amplifier that sounds as good or better than a single ended zero feedback audio amplifier utilizing 300B directly heated power triodes. Given that the 300B is so “underpowered” when it comes to hi-fi loudspeakers commonly available in “stereo shops” around the world, would a more powerful version of the 300B – but sounds just as good – represent the future of single ended triode audio amplifiers?   

Enter the 811 power triode vacuum tube which was developed by a St. Petersburg, Russia based vacuum tube manufacturer named Svetlana specifically for the high fidelity audio market of the 1990s. It was – and still is – an interesting new design being a modern high-tech vacuum tube specifically designed for high fidelity audio. The 811 has an anode dissipation of 65watts and a maximum anode voltage of 800V making it usefully beefier than a 300B vacuum tube, if a bit below the ratings of a 211 or 845. The 811 power triode vacuum tube stands nearly 6–in. high overall and has a maximum bulb diameter of just over 2-in. 

Svetlana has given the 811 power triode a thoriated tungsten filament which, they say, is much more resistant to overload in comparison to those vacuum tubes with oxide coatings. The 811 is a directly heated vacuum tube – there is no cathode – so it has a “soft glow” during its operation. Steadier emission over time from the filament gives a more stable sound, too. Internal parts are supported by ceramic insulators and mica supports brace the electrode structure against the glass to minimize microphony. 

A white ceramic base is used to enhance appearance and matching ceramic vacuum tube holder is available. Two types of 811 are available, low mu (3.5) and high mu (10) and with a standard 6.3V heater and a low price of just 30 US dollars (here in S-E Asia), the 811 looks to be a great value. The low mu version sinks more current and is more suitable for low-ish voltage working (say 450V) to stay within the voltage limit of electrolytic capacitors. The higher mu suits higher power supply voltages where it should prove a little more linear and it is also easier to drive allowing you to use a “better sounding” driver preamplifier tube like the ECC82 / CV181 instead of the 6SN7. On a price versus power handling basis, the new Svetlana 811 power triode looks untouchable and should become popular in the DIY audio scene.

Can the 8417 Vacuum Tube Ever Be Resurrected?

Despite the return of the formerly extinct vacuum tubes – like the 7591A vacuum tube – during the late 1990s, can the 8417 vacuum tube be ever resurrected for the benefit of 21^st Century audiophiles? 

By: Ringo Bones 

If you are “fortunate” enough to have started do-it-yourself high fidelity audio during the 1980s, you might find it disconcerting – especially for American DIY hi-fi audio enthusiasts – that it was the “modern” vacuum tubes - like the 7591A power pentode and 8417 beam power tetrode vacuum tubes - that became extinct, especially during the Reagan Administration. But given that the 7591A power pentode eventually got reintroduced by Electro-Harmonix during the late 1990s thanks to Jazz electric guitarists in the former Warsaw Pact countries, is there any hope for the 8417 vacuum tube to be resurrected? 

Historically speaking, the 8417 beam power tetrode is for intents and purposes a “modern” vacuum tube because not only it was the last ones to be developed and marketed during the latter half of the Golden Age Of Stereo back in 1963 before solid state devices of similar capabilities became commercially viable years later but also like every solid state audio amplification the 8417 vacuum tube is designed to work with various degrees of negative feedback in its operation. During its early days, the 8417 vacuum tube is described as a “cavity anode” type specifically designed for the Fisher SA-1000 audio amplifier.

The 8417 vacuum tube has a rated anode dissipation of 35-watts RMS that results in a 100-watt RMS output in push-pull AB1 fixed bias configuration that results in an audio amplifier using a pair of the tubes. Even though it first gained popularity in the Dynaco Mark III amplifier during the early 1970s, it was Quicksilver Audio that brought the 8417 vacuum tube to worldwide fame back in 1981 when the former founder and owner of Quicksilver Audio Mike Sanders began selling the Quicksilver MS 190 stereo amplifier. 

The Philips 8417 Mono Amplifiers were later developed in 1984 to bring that great vacuum tube sound to the average consumer. Harry Pearson of The Absolute Sound magazine published a positive review of the amplifier during that time. Philips managed to manufacture the amplifier until 1998 before manufacturing their batches of the 8417 vacuum tube became no longer economically viable at the tail end of the 1980s. Quicksilver kept manufacturing their versions of the 8417 vacuum tube amplifier well into the 1990s to take advantage of the 1990s era Hi-Fi Renaissance despite of the output tube becoming virtually extinct at that time.      

Given that the 8417 beam power tetrode vacuum tube has no “modern” equivalent – i.e. post Soviet Russian and post Warsaw-pact manufactured equivalents – various replacement schemes for the output tubes of 8417 equipped audio amplifiers were proposed. Owners of Dynaco Mark III amps that use 8417 beam power tetrodes can be “rebiased” to use the more plentiful and still manufactured 6550 vacuum tube, but unfortunately the Dynaco Mark III’s output transformers are primarily optimized for the 8417. Too bad nobody manufactured electric guitar amplifiers that used the 8417 vacuum tubes during the 1960s because if one company did, Electro-Harmonix would be remanufacturing their very own 8417 beam power tetrode vacuum tube back in the late 1990s. 

When buying new old stock – or NOS – 8417 beam power tetrode vacuum tubes, Sylvania are considered the best brand and is relatively widely available, while General Electric and RCA manufactured ones too with varying quality and some batches are prone to grid overheating in long hi-fi listening sessions. It’s best to consider buying General Electric and RCA 8417 vacuum tubes only when they are those of “specifically manufactured for the U.S. Air Force types” – i.e. reinforced anode military specification  mil spec  types. 

Is Live Music Really Better Than Hi-Fi?

The debate between live and recorded music has been opening countless cans of worms since the first affordable Victrola was launched, but is live music really better than hi-fi in this day and age? 

By: Ringo Bones 

Staunch supporters of touring musicians may have Napster creator Shawn Fanning to thank because ever since that time, the only way for “rockstars” to earn ungodly amounts of money is via touring and doing live concerts. But has hi-fi audio technology really advanced to a point since that time that a well set-up hi-fi rig this day and age can now rival the sound quality of a live music concert? Sadly, like all things in the real world, the “concept” of a live music concert wholly depends upon your perspective. 

Sometimes, I do find it strange on how most “hi-fi” journalists that are vehement critics of how different hi-fi music and live music – Classical or rock – are had never played live on stage during the last 20 years or so, never mind within their whole lifetime. Remember that scene in the Bruce Willis and Kim Basinger movie titled Too Hot To Handle - or was it Blind Date back in 1987? - when the two of them witnessed a “live-in-the-recording-studio” performance of Jazz guitar legend Stanley Jordan? Well, that’s my idea of live musical performance that our hi-fi rigs no matter how expensive still can’t touch though we’re getting there closer everyday but most tenured hi-fi journalist this day and age conveniently overlooks. 

By the nature of the beast, hi-fi journalists, more often than not, tend not to talk about the hard realities of being a touring musician – never mind a “roadie”. Remember that incident during the Extremist tour back in 1992 where Joe Satriani’s trusty electric guitar amps – i.e. Soldano heads and a 1969 era 100-watt Marshall amplifier were stolen in lieu to being transported from their touring truck to the stage? Equipment theft incidences seem to be furthest from the minds of these “tenured hi-fi journalists” when it comes to comparing between live music and hi-fi. During that time, vacuum tube gear were getting scare during the Reagan years – imagine if it were the “hi-fi journalists” McIntosh amp that used 7591A vacuum tubes? Try finding a replacement in two weeks time, never mind waiting for Electro-Harmonix to manufacture one in eight years time. 

Sound quality wise, rock bands that top my own sound quality list during their live performances tend to be the older ones – as in The Grateful Dead and Pink Floyd. But form the location – as in perspective - in the audience where I and most of us can no longer the direct sound of the unamplified drum set and most of what we hear is the concert PA system, I’ll stick with my home hi-fi rig thank you. From 500 feet from the stage, the last Pink Floyd concert I’ve been to back in 2002 has the PA system’s sound quality just slightly worse than a Denon PMA-350SE amplifier or a Rotel RA970BX amp connected to a Tannoy Westminster loudspeakers being fed from a 1995 era Linn Sondek turntable. 

Whatever Happened To Hi-Fi Gunshot / Gunfire Recordings?

Though the last time I saw one being displayed in my neighborhood’s record store, Miami Vice’s first season was just about to end, but are there any technical difficulties in making “audiophile” gunshot / gunfire recordings?

By: Ringo Bones 

Weird fact – even though sound effect CD’s featuring gunfire / gunshot recordings of widely varying sound quality are “more or less” are still stocked in most record stores around the world, not one of them claimed to be of audiophile or even of “hi-fi” quality. Politics aside, are there really technical difficulties in recording true “audiophile quality” gunshot / gunfire recordings that sound like the real thing when played in a well set-up hi-fi system? 

Maybe 1990s era Madison Avenue hi-fi admen overlooked the hype and potential big money of advertising an audio product that has the seal-of-approval by either Mikhail Kalashnikov or Eugene Stoner as being able to reproduce the sound of either an AK-47 or an M-16 assault rifle in full auto mode with the timbre of the actual acoustic event. And, believe-it-or-not, the topic of how your hi-fi rig replicates the sound of a modern assault rifle firing 5.56-mm X 45-mm NATO rounds can generate “howls of derision” in either Twitter or Pinterest despite the howler being unable to fully articulate their derisions in an erudite manner using 140-characters or less. 

Even though there are quite a “handful” of movies that got the gunshot recording right, like that “zombie apocalypse movie” 28 Days later where Cilian Murphy stars in, most gunshot / gunfire Foley – i.e. sound effects – used in movies are, timbre wise, far removed from the real thing. But are there truly “technical issues” that hamper in the creation of truly “audiophile quality” gunshot / gunfire recordings? 

Recent figures of peak decibel sound pressure levels of most small arms widely used in most Hollywood action moves are as follows: small rifle = 140 to 145 dB SPL, medium rifle = 157 to 160 dB SPL, large rifle = 160 to 174 dB SPL, shotgun = 152 to 166 dB SPL, small pistol = 150 to 157 dB SPL, large pistol = 158 to 174 dB SPL. Most microphones are capable of recording sounds up to 130 dB SPL – but only with its built-in L-pad switched in when recording jet-engine level sounds, but in practice, most microphones commonly used in music studio recording sessions tend to distort badly when recording sounds above 110 dB SPL – even with peaks lasting just several milliseconds. And L-pads have a tendency to add an overall “grunginess” that makes most recorded gunshot sound effects sound “less-than-audiophile”. 

Back in 2005, an episode of Discovery Channel’s Future Weapons were doing an episode on a new squad automatic weapon that uses 7.62-mm X 51-mm rounds instead of the older M-249 SAW that uses 5.56-mm X 45-mm rounds (I think it was M240L or the Mk 48) where presenter Richard Machowicz suddenly pointed out that they’ve just busted the diaphragm of their tubed ribbon microphone when recording the sound of the weapon. This highlighting the technical difficulties of recording sound pressure levels several orders of magnitude louder than a heavy metal rock concert. 

When it comes to recording live acoustic events these days – either music or ambient sounds – it always more often than not boils down to a compromise of choosing between a condenser microphone and a tubed microphone. Condenser microphones are known for their openness and more air while tubed microphones have a nice EQ sound without resorting to using too much EQ during final mix-down that could result in unwanted phase shifts that makes the recorded sound acquire an unnatural electronic timbre. Stereophile’s recording-engineer-in-residence John Atkinson overcame this inherent live recording limitation during the 1990s with his “time-aligned microphones” that combines the air and openness of condenser microphones with that you-are-there timbre of tubed microphones, but I don’t think he’ll be recording audiophile quality gunshot / gunfire recordings anytime soon.