I think one of the German mags measured similarly. If you look at the plate structure, it is basically the same as an Emission Labs 520B tube, just slightly bigger. I was able to do this comparison because I had the C3 and the Horning SATI amp, which uses 520Bs, at the same time I have also owned the Amare Musica Entropy Diamond that used the Emission Labs 1605 triode (its bigger than the 520B) but sadly, this amp didn't really sound very good, despite being all DHT (the input tube was a 20B DHT from Emission labs). That was one of the bigger disappointments I have owned recently.
SET amp owners thread
- Thread starter bonzo75
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@morricab
I tried once with Duo Omegas the micro SET of 1 W, barely bigger than a match box.
No problem with driving Duos
I will PM you the list of upgraded items in my C3.
I tried once with Duo Omegas the micro SET of 1 W, barely bigger than a match box.
No problem with driving Duos
I will PM you the list of upgraded items in my C3.
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Tube amps vary but are often less than that if they employ feedback.
The Harmon Kardon Citation 2 from 65 years ago was 0.5% at full power. Futterman's OTLs from the early 1960s were 0.05%. The Dynaco ST-70 was rated 0.025%.
Most SETs, owing to zero feedback, are 10% THD at full power (clipping). The Jack Elliano's Ultrapath circuit allowed about half that. Sometimes you see lower distortion in the specs, which is often the amp specced at a lower power rating below clipping.
Can you provide specific empirical measurement statistics for specific amplifiers … Or is this merely generalising once again ?
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It would be interesting to see the spec across 20 differently better know manufacturer of SET and highlight the distortion levels.
With which output tube? You realize that this has the biggest effect on how much power can be generated with a given distortion level? What would you do with THD data? Do you think you can assess the sound quality based on that number?
If you want to know more about the new MTA (Multiplied Transconductance Amplifier) by Frank Blöhbaum, you have to pay and read this article. Briefly described, you give a triode the distortion values of a modern transistor without destroying the character of the triode. For example, at full power 0.05%thd.
Article Linear Audio Vol. 6 & 8.
www.linearaudio.net
A little teaser boosted 6sn7
P.S
Blöhbaum Gm 70 SE tube amp 54 Watt at high end munich took longer to find the photo ...sorry.
Article Linear Audio Vol. 6 & 8.
Linear Audio Volumes | Linear Audio
P.S
Blöhbaum Gm 70 SE tube amp 54 Watt at high end munich took longer to find the photo ...sorry.
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300b in ideal circumstances
2A3 in ideal circumstances
211 in ideal circumstances
type 45 in ideal circumstances
You'll see that the power tube by itself is making about 5% THD at full power. Any driver and Voltage amplifier will of course add more distortion since there is no feedback. Usually such tubes like the 6SN7 don't have a distortion spec in the same way that power tubes do. This does not include contributions from the output transformer.
So any SET amp circuit is going to have more distortion than merely that of the power tubes. 10% is a very common value- this is just at clipping, when the sine waveform is bumping into the amplifier's limits. Stereophile does not like to show distortion above 1% so most zero feedback tube amps are no-where near clipping in their measurements FWIW.
So my comment is a generalization; based on having designed such amps, knowing the actual numbers the designer is up against (such as the tube specs above) and also from having seen how some amps are rated, which is to say I've seen exaggerated power figures and the like. If you look at these tube specs and then look at the power claimed by some manufacturers, along with the distortion (if they even make that claim) its easy to see the numbers don't always add (or multiply) up. So now you have a tool; for example if you see a 5-Watt 2A3 amp boasting 5% at full power, you know by looking at the specs that something isn't right.
In the 1950s, David Hafler was awarded a patent for his Ultra Linear concept wile working for Acrosound. Landford-Smith did some measurements of distortion and showed that UL is actually lower than either pentode or triode operation:
https://pearl-hifi.com/06_Lit_Archive/02_PEARL_Arch/Vol_01/Sec_02/081_Ultra-linear_Amps_w_Refs.pdf
Its possible to operate a pentode in class A, single-ended UL operation and obtain lower distortion numbers with no feedback. As the patent shows, there is a particular tap percentage for optimal operation. To bypass the patent, other amp companies (including Dynaco where Hafler was employed after Acrosound) deliberately set the tap percentage slightly off, which has become tradition (IOW, everyone does that nowadays despite the patent being long expired). If the tap percentage is set correctly you obtain curves that allow for more linear operation. FWIW this gets you similar sound quality and lower distortion for a lot less money as most pentode tubes tend to be cheaper than most triodes.
You can also reduce distortion by things like the Ultrapath. But on looking at SET amp websites, I don't see a lot of mention of that technique. This leads me to believe its not being used that much. So yeah, 10% at full power before clipping is pretty close to most SETs.
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