Question About Capacitor Upgrade in Tube Amp

Let’s begin with the fact that capacitors are among the most non-linear parts of any amplifier -- so any real improvement is worthwhile. I don’t know what the existing caps are so none of us have any basis to comment on the upgrade value specifically.

Let’s assume they are not the best.  Would be better if you said. Do you even know this to be true?

You discuss two types of capacitors: 1) coupling caps which block DC and allow two stages to to be linked, pass the music signal, but allow two different DC points to exist. These are directly in the signal path and a better cap means a better signal. 2) you discuss what is called a bypass capacitor on the power supply (B+ to ground). Broadly speaking we can think of capacitors (electrolytic primarily) that are efficient, with large capacity for their size, and cost, but are very nonlinear, especially as frequency rises. Alternatively there are various classes of capacitors that are the revers - large size, small value, but very linear and good sounding. Good design combines the two allowing one to provide capacitance and the others to provie linearity and efficiency at high frequencies. The best of these are film type capacitors (Mylar, or better yet poypropolene). Ceramic are also very good but have only tiny values or low voltages for the monolithic multilayer types (like << 50V).

You can pretty much know what will be the best sounding from one value: dialectic absorption. A Poly type is typically something like 100X to 1000X better than a "lytic.

As to whether they matter: yes. They make the power supply, well, supply, at high frequencies!

So get polyprop caps of >> whatever the applied voltage is (more is better, but gets $$ and big) and put them in. Poly caps are NOT polarized, but there is often a band that indicates the end to be grounded.

Justme.

So, in case that was too techie and long, yes replace them all (if the ones you already have there are poor, we have no idea really).  My two cents replace them with polypropolene films caps of the same or slightly higher voltage and the same capacitance (or more for the bypass).

Dont worry about brands.  Paper is long term unreliable.

ANY cap upgrade is useful, power supplies included.

In general, the type of capacitor is more important than brand. From cheapest (and least good) to best: metallized insulator, film and foil, air gap, vacuum. There is a good discussion of this in 'Art of Electronics.

Next most important are the materials: polypropylene, styrene, teflon (insulators); aluminum, tin, copper, silver (conductors).

Polypropylene is not as clear, teflon can be a little harsh. To my ears, styrene is just right. Conductors are not as important, although there are differences. Aluminum is prone to corrosion and can be a little harsh. Copper is expensive. I find tin to be a good compromise.

I mainly use air gap and vacuum caps for the most important components, such as RIAA compensation. For amps, I usually use styrene.

For brand, I use MIT or Relcap for signal path, Solen for power supply. Phono stage uses Solen teflon for the final power supply filter. Good luck!

YMMV

From my understanding the existing non-polarized caps are silver film. I do not think they are junk but for a reasonable cost certainly am willing to upgrade them.

So no love for the Mundorf Supreme SGO 1000VDC caps here? I had originally been thinking of those.

And thanks for the advice to replace all three of them.

The electrolytics are Nichicon so I will leave those be.

The small film caps that are put across the electrolytics, are bypass capacitors.

A small high quality bypass cap can greatly improve the SQ from the bigger electrolytic.

I recently recapped a tube amp and I put Myflex capacitors with great success.

Also recapped a Marantz 7T and because of space restrictions, used Audionote electrolytics with Myflex bypass capacitors on each one. Also sounds fantastic.

Deoending on how long you plan on keeping the amp, buy the best capacitors you can justify putting into it. They will make a difference. Humblehifi’s capacitor list has served me well in the past when deciding on what caps to use.

And ignore the comments about your amp not being worth the effort. It’ll be worth the effort. Anyone who has done a recap, either themselves or by a tech will tell you it’s worth it.