What value cap to bypass power supply cap?

Dracule1 .. my post was a attempt at painting a picture with broad stokes ... and suggesting the number you were seeking was 1/100th or 1% as Kijanki stated

My post got you in the ball park but seated you in the third deck .. Kijanki's guidance has give you field level box seats 3 rows behind first base

6 years ago I upgraded the PS caps in my D500 Phase Linear .. I bumped the main caps from the factory stock 35k to 140K of Nichicon’s and bypassed with 1% Rels .. I also had a dual diode bridge installed and eliminated the stock factory attenuators by wiring the inputs directly to the outputs eliminate the old carbon pots and about 4 feet of wiring

The difference was far from night and day ... much more like dusk to dawn ... but the improvement was positive with no down sides .. tightening up the base and opening up the treble very nicely

I think the Rel’s helped extend and open up the treble and the Nichicon’s gave some boost to the bass

I have found greater gains in working with room acoustics .. power deliver and vibration control .. but have no complaints about the amp upgrade to this day .. that amp isn’t going anywhere nor are the double run of Ridge Street PIII speaker cables driving my NHT3.3’s

Dracule1 .. I’m sure you’ll agree with me that they should put Kijanki and Almarg’s picture on money for all their contributions and time donated to this forum

ATB Dave
.

Thank you Dave for good word but I'm only trying a little to repay all great thing I learn on this forum. Almarg is is the one to be praised for sharing his knowledge and constantly helping people. He is pretty much a guru for all technical things.

Hi Kijanki, I think what you're talking about is putting a single cap at the input as an AC line filter. That is a great place for Mundorf Supreme. People have already tried this out and got good result:

http://www.laventure.net/tourist/caps.htm

However, as you can see in the link, there a caveat with Mundorfs as AC filter...It is note rated for use in AC application.

I have been told by several amp designers that bypassing each power supply cap with a 0.1 microF (or other small value cap) is good design practice to filter out noise in the hundreds of kHz to megaHz range, which I was told can cause unwanted oscillations in the amp.

Thanks for hanging in there to guide me.

Hi Davehrab, thank you for your input. When I started this thread, I was confusing several things about bypassing. Here is what I've learned so far from helpful people like you and Kijanki. Please correct me if I'm wrong.

1) The 1% bypass cap recommendation is to reduce ripple in the power supply. This helps with the frequency response of the amp (not exactly sure why) and decreases noise generated by the power supply.

2) Film caps have higher self resonant frequency than electrolytic caps, which is a good thing because it is farther out from audible frequency range. Film caps have much lower ESR (and ESL?) than electrolytics. Do these properties of film caps mitigate the need for the 1% bypass cap recommendation that is employed on electrolytics?

3) The 0.1 microF bypass on each power supply cap and also on the amplifier end helps filter out the really high frequency noise (hundreds of kHz to MHz) range that can cause unwanted very high frequency oscillations in the amp. Some have argued just filtering out the high freq hash may even affect sound quality (not to sure about this argument).

I hope someone will correct me if any of my statements are incorrect. I am learning so much on this forum. Thank you.

BTW, I have replaced the carbon pot on my amp with stepped resistor attenuator. A significant improvement. But the most significant improvement came from treating the room acoustics...took me over two years with various combinations of absorption and diffusion. Phase Linear?...Bob's solid state amp. I'm a fan.

Dracule1, no I would not recommend Mundorf for AC line filter. What I meant is that all your caps are most likely connected in parallel and then to the amp's circuitry. At the input to this circuitry I would put 1uF cap.

When you connect caps in parallel wire going to circuit should be from the very last cap and not the one close to rectifier.