Question About Capacitor Upgrade in Tube Amp


I am preparing to do a coupling capacitor upgrade on a recently purchased tube integrated amp. The two 0.22uF on the preamp tubes are fairly straight forward. But I noticed another similar model 0.33uF cap on the large filter capacitor for the B+ supply that is installed across the hot lead to ground.

Does this cap on the B+ just block high frequency noise from the power supply or does it have any effect on the amp tone? Is there any reason to "upgrade" this cap?

I know it may be hard to tell exactly what is going on without a schematic.

Also any recommendations on a good cap to use in the upgrade of the coupling caps? I was looking at Mundorf SilverGoldOil for the quality at not too crazy a price. The amp already sounds good but lacks a little clarity that I think a coupling cap swap will help with. It is SET 300B amp.

Thank you!




Completely unnecessary obnoxious and immature forum behavior.


@jaytor And most important, these amps have LETHAL voltages inside. Capacitors can hold a lethal charge for a long time.

So I should have been careful soldering that bypass cap on the 330uF 450V Nichicon filter cap from hot to ground terminal?

Oh dear maybe that is why it was so exhilarating doing the upgrade. A real exciting experience.



But seriously that is good advice. Use the sorting cable with a suitable 10W resistor to discharge electrolytic caps first.

I have dorfs in my 300b amp does it sound better because of them? maybe. 

Each type of capacitor has a specific frequency response and voltage related distortion.

It should stand to reason that better constructed capacitors should have a better frequency response and less distortion. Whether you can hear the difference in reality or it is simply a fresh capacitor not being run in yet that sounds different I do not know for sure. But it seems in my case there was an improvement in frequency response and lower distortion replacing the cheap factory caps with one of better and different material construction.

In this article the title seems to take the opposite opinion but have a read thru and there is some information that at least confirms capacitor construction does impact sound quality.



Resistors make a difference too. I tested half a dozen candidates with a rotary switch in my preamp. Nude Vishay resistors were the best, no-name metal films from Taiwan second, aerospace hyper-expensive last.