Upgrading specific components in a tube amplifier

Upgrading parts can certainly be worthwhile, and can be audible, but what you prefer is always subjective. Be aware that some caps take some time to burn in, and don’t always sound better immediately.

For me, recent mods started with adding a VTA board to my Dyna 70s. In addition to a different driver stage, those mods also beefed up the power supply. At the same time, I upgraded the coupling caps, resistors, and internal wire. It’s tough to be certain what contributed to specific changes, but the whole amp sounded better across the board to me. Switching to a solid state rectifier followed.

Tube rolling can lead to some significant audible changes too, and while not usually inexpensive, they don’t typically involve any modification, assuming the amp will accept the tubes types you try, so it’s easy to experiment if you’re willing to obtain the tubes.

Lastly, my tube amps are now bi-amped, have an inline high pass filter before the amps, and only power the midbass and tweeters from ~ 60hz up. The woofers go through an active low pass crossover and are powered by a SS amp below 60hz. Relieving the smallish tube amps of the responsibility of powering larger woofers in the lowest octaves most definitely led to improved clarity, and in my case was relatively easy and affordable to do.

Once again thank you very much for taking your time to write so thorough responses to my inquiry. 

 

Are you doing it because you want to have fun and enjoy the hobby?  Are you making a repair and it is an opportunity to possibly improve a short coming? Are you dissatified with the piece of equipment?  [Would it be cheaper to sell the gear and invest the money (including what you might spend on parts and labor) into something better.  Can you afford to write off the investment in the equipment you are modifying?  (Somethimes it can be real hard to sell modified equipment.)]  

Relevant and necessary reflections that I believe one should carefully consider oneself before proceeding with these major adjustments.

Figure out which resistors and caps you're looking to upgrade, post the values and where they are in the circuit, and current brand, and you'll get some good recommendations.

As I mentioned I'm considering Yamamoto Sound Craft VT-52. It is supposed to be an astonishing amplifier made of high quality craftsmanship.

After reading the article of switching components here and there, I started wondering how that would work on a Yamamoto amplifier. II have a pair of Audio Note speakers, entry-level, although they may be upgraded to AN SPe/HE very soon. Then I started to play with the thought of changing bits of Yamamoto to Audio Note components (capacitors, resistors and perhaps tube sockets as I heard Yamamotos aren't the best) to see if you could improve the amplifier a tiny bit. Perhaps it could also promote synergy with my speakers, who knows... 

The intent is not to have a Yamamoto amplifier that becomes a clone of Audio Note but rather, identify if there are components within the Yamamoto circuit that could be improved. 

Having overhauled a vintage tube amp from the chasis down, I would say the 3 most noticeable component improvements were the big smoothing caps, any  old wax caps and  the big one... tubes!  It was obvious when it happened but it took me 4 years to find a good strong set of vintage Japanese tubes for a vintage Japanese amp. And no doubt a british built amp would sound best with tubes made in the UK of that era also. 

Many of you mention tube rolling and I can't wait to indulge in this exciting activity, even though it seems it won't be as cheap as somebody claims. The Yamamoto amplifier I'm looking at uses the exotic and rare VT-52. 

Perhaps I should try to restate my question and present it in a hypothetical way.

If I were to switch resistors to Audio Note Silver Tantalum/Niobium 2 watt, change the output capacitors to Audio Note silver foil capacitors and change the tube sockets to Audio Note aluminium/steatite bases in a Yamamoto amplifier. Would it have significant changes to the presentation of the music? Please bear in mind this is a thought experiment. 

@carlsbad2 Thanks for the detailed information in your posts. What’s your answer to the other question the OP asked:

In your experience, do such modifications lead to noticeable improvements in sound quality?

I don’t see that you’ve relayed what you’ve found noticeable and I think this is a key trigger point for the OP (and others). Given your technical expertise, I’d love to learn about your subjective impressions of, say, how much a capacitor or other change leads to improvements which can be heard.