Single-Ended Triode (SET) Amplifier Revolution of the 1990s. Did it really happen? Was it Successful?
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I have measured with a analogue oscilloscope as well, but the Fluke I normally use is just a digital multimeter with a minimal sensitivity of 0.5mV AC.
Any hum will be from the amplifier, not the heater/filament of the triode. If the filament is powered correctly by the amplifier then there should be next to zero hum anyway. Filament hum is dependant on the amplifier design, in particular the filament circuit and whether its AC or DC supplying the filament. If your 300B amplifier is prone to hum then it probably has AC feeding the filaments, in which case there should be a hum bucker circuit in the amplifier, where you can adjust or buck the hum out to acceptable levels. This is far from ideal because as the tube ages the hum can reappear and then it requires further adjustment. FWIW we had an 300B amplifier here a few months back with a pair of the latest production WE 300B's, but one of them was very noisy. It was not a hum, but a rustling noise that was present while the amplifier was on. The owner sent the 300Bs back and the noisy one was replaced by WE. With todays circuits it is possible to have zero hum (50Hz or 100Hz) on any DHT based amplifier.
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Graham, mildly off topic I know, but what did you think of the new prod WE 300B? I run an AirTight ATM300B w/ WE 300Bs about 1996 production (when I bought it from Arturo at AXISS), RCA red-letter 12BH7s, orig GL Genalex B749s and a c. 1940s RCA 5U4G rectifier. Just curious, respect your ears...
Indeed, the hum is at such a low level that most speakers with less than say 106dB sensitivity will not hear it at all. And yes, turning the hum bucker can cause the hum to increase or decrease. But with the other 300Bs, some tubes are not so stable and one needs to adjust the hum bucker from time to time. With the WE300B, I have not noticed this. The 300B heaters are fed with AC. People have debated the merits of AC vs. DC heating for DHTs for a long time, but purists tend to stick to AC.
Indeed they have. Trouble is that triodes like the 300B are extremely sensitive of filament voltage and current. Even 2% to 3% (mostly below 5 volts in the case of a 300B) will have a significant degradation on the audio performance. Most of the 300B amps I have had through my workshop over the years have never made 5 volts. Most are around 4 volts and because they are AC heated they cannot be adjusted or corrected to make 5 volts. This is made worse due to the filaments of most 300B's not being the same. Example: the WE 300 draws 1.2 amps, others like the EML 300B (WE copy) draws 1.3 amps (actually its a little more). The EML 300B-XLS draws 1.5 amps (also its a little more and nearer to 1.6 to 1.7 amps) which means the filament voltage will be much lower due to the increased current draw (increasing the current draw means the voltage drops). In most cases very few audiophiles rarely hear the full capability of the 300B for this very reason.
Regarding hum and high efficiency speakers: First we have to look at the speaker. Quoting an efficiency and amplifier hum is meaning less if the speaker doesn't do the whole frequency range, as in 20Hz - 20KHz (+/-3dB). Many high efficiency loudspeakers don't go low enough for the hum to be a significant problem so its not heard, or if it is heard it is of such a lower level as not to be noticed. Example: the Cube Nenuphar has a bass spec of 28Hz - 18kHz (-6db) meaning that at 28Hz the sound is -6dB down. So the 50/60Hz will probably not be heard. However, with the introduction of full range horns about 25 years ago, most with powered subs or active bass horns, means that amplifier hum can be a huge issue. This is especially true with SET amplifiers which are directly connected to the powered subs/basshorns, as the amplifier hum will be amplified and EQ'ed by the subs/basshorns down to about 20Hz, and this will be audible in the listening environment.
From a UK perspective - I think in the late 80's early 90's Peter Qvotrup intoduced the KSL/AUDIO Note Ongaku. BAck then £34,000 using snell horns, fronted by the Voyd reference using a Helius Cyalene. I know HiFi Choice and What HiFi in the UK went gaga over them. It popularised the notion that if things don't measure well it means nowt in terms of musicality. I've not heard this famous audio chain. Valve amps became significantly more commercially available such as Audio Innovations too. Remember until then the Krell KSA's were seen to be the holy grail of audio driving Aprogee Scintilla's - IMHO still an astonishing combo.
Actually, Bé Yamamura was the first to bring SET amplifiers to the UK prior to Audio Innovations and Audionote Japan. These found their way to Radlett Audio and Abbot Audio in the mid 1980's. Bé is an extremely well thought of designer in Japan. Back in the day, if he wrote a technical article in a Japanese HiFi magazine, about 6 Japanese companies would produce their version of his design. The RS Labs tonearm is an example of this. Also, Snell didn't make horns. You are probably referring to the Snell Type A speaker which was a very large box design with a 3 way driver system (86dB) and for its day it was highly regarded.
I aver to ur better understanding- I am going from my knowledge as a consumer at the time as a poor student who amassed a hifimag collection. From what I recall audio note and audio innovations were widely promoted - as to the Snell horns - my bad - I always thought it was a horn - so thanks
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Every time I’ve heard one they sound wonderful and musical - that said I’m not a fan. I’m not sure it’s fair to call them a fad given that their topology has withstood the test of time since about amps were first made in 1912 by Lee de Forest (less of a fad than cables and fuses - )
Just for information: I imported the original AirTight ATM300B into the UK about 20 years ago along with the other AirTight amplifiers so I know all their amps quite well.
Regarding the new WE 300B's: well I guess like all new products that come to fruition, either from a new design, or a new production factory, it is always best to leave it for a period of time before purchasing, just to make sure the production batches and quality control issues have all been addressed, and in this case, the tubes are good and reliable. I have several pairs of the last production (dated around 2000) and these were very good indeed. I also recently had a new pair from the current production, well the ones that came out about this time last year (2021). Unfortunately one of these WE 300B's had a serious noise issue, so it had to go back to WE. Western Electric replaced it FOC with another new one and now both appear to be noise free. In the mean time I had to supply a pair of EML 300B's, the WE copy, to replace the WE version, as I have found the EML to be good and also reliable. Currently, I have not heard enough of the new WE 300B version to say if it is better or worse than the previous generation. In theory they should be identical, all I can do is to report back when I have had more experience with the newer WE version.
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Way less a fad than any tweaks
The triode came in 1907 and as you say Lee de Forest established various iterations of amps working with the triode valves from around 1912 and triode based amps have persisted (at varying levels of market share) among all the various topologies of amps right through to the present day so it’s hardly a fad. I’d figure the building resurgence in single ended triodes since the 90s and continuing growth over these last three decades seems to me much more of a lasting renaissance.
All the differing types of amps aren’t for everyone. Each changes our experience or perhaps tilts or shapes the focus of our listening and for me it all just points to differences of preference and our wanting different balances in states of being within our experiences in listening.
Transistors came to us initially in the 60’s and began to dominate in the 70’s and then fast switching mosfets and switching amps came to the mix in the mid 80’s. I’ve lived with all fundamental types (with the exception of class d amps) and use SET when I’m primarily interested in engaging in a very direct and immediate connection with music… these days I listen via SET unless I’m wanting music as background to work or as background for partying. The best dance rig I have still has SET amp driving the music but much exposed high voltage big direct heated triodes and alcohol and dancing can be a rather hectic and volatile party mix lol
A return to SET for some just is seeking a different (and for me what I experience as a more direct) kind of relationship with music and sound. But it’s different for all of us and just about preferences. Perhaps moving towards different gear is just a part of each of us evolving and changing our relationship with the phenomenon in listening and music and then in shaping all the varying expectations we develop within these listening experiences.
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It makes me happy to know that you have a dance party rig
It makes me completely happy as well… I worked in nightclubs in my earlier days and my family owned some as well and when we were younger various hotels and bars… and then there was the dance scene in the 80’s and 90’s… the body may have a bit less stamina but still the dance demons hold some sway.It makes me happy to know that you have a dance party rig
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No fad, people are judging with their ears and many are finding more "truth" in the SET amplification.
All you need is an 80’s mullet haircut from the front short and serious - from the side party at the weekend
Just before the lockdowns began a while back we got together for a reunion of a band with a mate I went to high school with who played in a pub band that played music by The Cure, The Smiths and The Clash… loved that, was joyful and wild to be able to go back to that time.
Late to this thread I realize, but as a recent member and long time SET listener, I can safely say that the “SET revolution” was successful as per my personal experience. In the late ‘90s, after looking for a simple sound system to replace my NAD driven Thiel speaker system I lucked upon a pair of mono Korneff 45 Tube driven amps. As these things go I started with a Sony CD Walkman feeding the Korneff into a set of bookshelf speakers. I still have the Korneffs but they now feed into a set of Beauhorn Virtuoso with Lowther drivers. I moved from the Walkman eventually to an Audio Note digital end and a Spiral Groove TT. In all of these changes I’ve kept the Korneff 45 monos in the system. Perhaps there’s another 45 amplifier out there that will bring the music closer but I haven’t been looking, just listening.
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