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In Reply to: RE: recommendations for an SET integrated amp posted by saki70 on April 28, 2017 at 04:52:57
I made an error - I meant Single Ended Pentode with regards to the OTO. It basically just gives the OTO more power - as there is no comparison to a lower power version - I can't make a comparison.
With parallel (two tubes) versus (one) it is basically doubling the power. The pitfalls mentioned below I suspect depend largely on who is doing the designing and how good they are at avoiding pitfalls.
Parallel versions over more power (double?) and seem to add some more stability and control of bass drivers. For instance I am not much of a fan of the 300B as I find them quite weak willed (Hong Kong dealer calls them "lady amps") which implies they are nice for singer at a piano kind of stuff but fall apart on demanding material - the parallel 300b IME does not.
This is very true of the Empress 2A3 which actually bowled me over with its seemingly bottomless pit of power bass and drive. When I was playing Split the Atom with pelting trance bass lines - I had to shake my head that this was 7-8 watts on relatively modest sensitivity speakers.
The one tube stereo amp version (name escapes me) couldn't really do it (though it might on 100dB sensitive speakers. I didn't hear any sonic advantages with the single tube versions. Whether there is with other brands I can't say.
But I think AN probably does SET amplifiers as good as SET amplifiers can be done and because they make so many amps - you can actually audition 1 and 2 tube versions of the same amp. Single 300B, Parallel 300b, Single 2a3, parallel 2A3 and I believe also 45.
You really have to decide. I really like the AN Empress - to me it's the best value for the dollar amplifier that Audio Note makes. But I also know others who greatly prefer the 211 or 45. So it goes.
You wrote..."Paralleled tubes produce greater power and simplify transformer winding somewhat. They are also harder to drive (increased Miller C), place more demands on power supply and cathode bypass design (larger C required for equivalent performance). Moreover, they introduce the variable of trying to match the two tubes as they age - no two tubes perfectly match and that situation is likely to worsen with age."
Can you explain why the paralleled tubes , aging at different rates , would affect the final output ?
Thank you .
Audio Note amplifiers all autobias. I have not heard anyone say there were any of these problems with any Audio Note amplifiers. Can't speak to lesser designs using lesser quality parts.
You may want to direct the question at 91derlust or indeed send an e-mail to Audio Note asking them about tube drift in a parallel designs to see if this is an area of weakness.
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