Your journey with lower-watt tube amps -- Can a kit be good enough?

Hi @atmasphere ,

 Power supplies of all vintage tube amplifiers from 50-60x look so miserable with such small capacitors.  It is especially true for stereo amplifiers when PS is used for both channels in parallel without any separation. I can say for sure such a PS will not work for a SET amplifier without feedback even if it is just 2 watt power.   

How does it work in all these vintage amplifiers? Does feedback make them less sensitive to PS or the reason is the push-pull topology?

@alexberger Do some of these vintage amps use a choke in the power supply?

Hi @invalid ,

Yes most of vintage amplifiers use chokes in power supply.

But they use very small capacitors in B+.

The issue with small capacitors is not the 120Hz noise from AC , but voltage stability during playing of load and complex music.

Nice blog post on SETs recently, here.

A few excerpts. It’s not a long post and worth a read:

"The SET’s very existence calls into question fundamental beliefs and assumptions we routinely make about technical performance, sound quality, and the correlation between them. These amplifiers expose a crack in the edifice of audio engineering theory that is based on the conviction that an amplifier can be judged by its technical specifications or measured performance....

This paradox arises because the technical measurements that attempt to quantify amplifier sound are simply inadequate and incomplete....Predicting an amplifier’s sound quality or judging it to be good or bad based on existing criteria is like looking at a few still images from a movie and then attempting to discern from those static photos the movie’s plot, characterizations, dramatic arc, and meaning.

The SET exposes the fact that certain aspects of amplifier performance are not quantified by the traditional measurement arsenal....

Some will suggest that listeners are merely responding to the SET’s euphonic distortion—that the SET sounds good because of its distortion rather than despite it. There’s no question that the largely second-harmonic distortion component of an SET is much more sonically benign than the upper-order distortion components of Class AB solid-state amplifiers. But a first-rate SET amplifier’s magical qualities go far beyond this simplistic interpretation. The SET’s resolution of inner detail that, singularly, conjures up a strikingly vivid picture of the instrument creating the sound is certainly not merely a euphonic second-harmonic distortion artifact....

This essay is neither a renunciation of all amplifiers other than SETs nor an evangelical campaign for the world to embrace the single-ended-triode amplifier. SETs are limited in the loudspeakers they can drive, exhibit other practical drawbacks, and are certainly not for every listener...."

https://www.theabsolutesound.com/articles/the-single-ended-triode-paradox/

I've long agreed with Harley after having been through virtually all classes of amplifiers, both tube and SS. Virtually certain most of those amps measured better than the SET's I've owned, yet none provided the immediacy, the resolution, transparency, and the micro dynamics of my SET's.

I posit at least part of this quandary is a function of low parts count in SET. SET doesn't have to negotiate multiples of caps, resistors, transistors, what have you, and if point to point wired no circuit board. I can hear sound quality differences with a changing out a single resistor, cap or hook up wire, this goes to show how transparent these amps are. I used to have to change out multiples of these items in other amps to exact a change in sound quality. This suggests a signal passing through a less circuitous route is less changed/affected/contaminated, in other words more pure to the source.