Question About Capacitor Upgrade in Tube Amp


Hi,

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!

 

calieng

As for capacitor used to shunt DC power supply, they are necessary to eliminate high-frequency noise present there, but never affect the sound quality as much as a different coupling (serial) capacitor used in the audio path.

@eworkflow Are you an engineer? Do you have a test lab? Verified the bypass capacitor values actually sink just the noise and haven't changed the DUT frequency / phase response?

'Noise' is not a constant and changing capacitor value / type may actually make things worse.

Changing type / value changes the power supply impedance and phase. Whether or not it is an improvement may be dependent on the DUT, the rest of the system AND the CBLF*.

Making willy-nilly recommendations is irresponsible.

*: the listener with all its inconsistencies.

@ieales I don’t know what social setting you acquired your accusatory tone from, but your ridiculous accusations of me being irresponsible have no merit. First, I wouldn’t suggest changing it to anything different nor ever stating that capacitors do not affect sound in the audio path. So, in short, I am "irresponsible" for saying that the primary role of low-capacitance capacitor shunting DC power supply is to filter HF noise. Secondly, please present a literature source to confirm your "power supply impedance and phase" being audibly affected by a low-capacitance shunt capacitor or just shut up. I am well aware of the fact that power supply quality will affect sound, but you are taking your holier-than-thou mission too far.

@eworkflow 

Agreed. 
Completely unnecessary obnoxious and immature forum behavior.

Charles

@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.