Question About Capacitor Upgrade in Tube Amp

I would also suggest that Dielectric Absorption (DA) is the most important measure for modding, because the other measures should have been considered in the design phase.

Nope. DA is not the most important by a long shot.

Of properties mentioned this far, left out are:

• Geometry, rolled or folded
• Lead material, length and attachment methods
• Foil material
• Foil inner / outer connection direction for DC blocking
• Microphonics
• Age

The properties you list are critical when using electrolytics, which are not (should not) be under consideration here.

OH, yes they should. Trying to clean up a marginal supply with a magic bullet is silly and rarely effective. A better supply can transform an amplifier.

Capacitor technology has improved immensely in recent years. More capacitance in smaller packages with reduction in ESR, ESL.

@ieales

Agreed that those properties have not been mentioned. But which of them do you consider more important than DA? You seem to have left that thought unfinished.

You say, "OH, yes they should." But my reading of the OP is that the question concerns coupling and bypass caps. Are you seriously suggesting bypassing with electrolytics?

Of course modern electrolytics are better, but that is not the question as I read it.

"On SET amps the key here is not just Caps, resistors and etc but the trannies are the keys elements which will make the amps sound best. "

Not on SET amps - on all music reproducing or generating equipment. Thats like saying "The key on binoculars is having a good lens!", as if cameras, microscopes, etc don’t need that either.

The second most important thing to keep in mind is don’t let anyone say to you, "I doubt this change will matter because of X Y Z position or capacitance etc". They dont know what you have to begin with, and the part may be so cheap it causes a lot of damage to the audio because of its physical nature. Replacing it with audio-grade may make a world of difference, no matter where in the circuit it is. A Leica lens may have 20 glass elements which serve a different purpose in the schematic, but if glass #14 or #4 is made out of ikea plastic, replacing it will naturally cause a huge improvement.

Recently I had my eyeglass lens replaced with a very high grade material for 2x the cost, and while the Rx was still slightly off, the overall experience of contrast, detail, color, distortion, was far superior. The optometrist thinks only in terms of his narrow view of measurements, getting the focus to land correctly, which is important. But won't usually talk to about the myriad of esoteric enhancements a better material brings, even with the wrong Rx. Audio in electronics is similar, hence why many systems dont measure well or are accurate, but present special qualities of music.

But my reading of the OP is that the question concerns coupling and bypass caps. Are you seriously suggesting bypassing with electrolytics?

BEFORE worrying about bypass or blocking caps, ALWAYS ensure the electrolytic PSU filter caps are up to snuff. Way too many tube amps have inadequate primary filter capacitance. Dropping the 120Hz by 10dB is far preferable to 100kHz by a couple.

Too often they are under voltage, too high ESR, too small, etc.

@ieales   Absolutely. Total agreement here. LC - LC forever!