Determining value of bypass caps?

[u1022186]

Hi Everyone. I need a little help with a recapping project I strted. I was thinking that as long as I"m recappinng my amps, I'd also do my Hafler DH-101 preamp. How do you determine the value of the caps to use for bypassing the electrolytics. I see where others have asked, and they were just given specific values to use. But how do you actually determine those values? And for the power supply caps, should I increase their capacitance value, and if so, how much of an increase is safe. And would that require changing any other parts. I've only been worked on some computers in recent years, and haven't touched audio equipment in almost 25 years. It's been a long time since I had to worry about how capacitors sound. Thanks, Bob

[nigelwright7557]

I dont tend to use bypass capacitors in my amp designs just smoothing capacitors.

However the usual value is somewhere between 100nf and 470nf. Its basically to soak up spikes on the supply lines.

[u1022186]

I was referring to the caps that are put in parallel with the electorlytics to smooth out the high end. I see some people calling them bypass and some smoothing. Not sure which term is correct. I was just wondering if their was a formula based on the value of the original cap it's paralleling. Thanks, Bob

[nigelwright7557]

Originally posted by u1022186
I was referring to the caps that are put in parallel with the electorlytics to smooth out the high end. I see some people calling them bypass and some smoothing. Not sure which term is correct. I was just wondering if their was a formula based on the value of the original cap it's paralleling. Thanks, Bob

Because electrolytic capacitors can be inductive at higher frequencies and they also have an effective series resistance they dont short out high frequencies very well.
So a small value capacitor is put across the electrolytic to get rid of high frequencies.

The values I gave earlier are typical values.