PSU bypass caps

[Sunsun22]

I've soldered additional caps (39uF 35V Panasonic FC) on the +V and -V rails to the ground on the opamps in my preamp. The punch improves a lot. When I started to solder PSU bypass caps (0.1uF 50V multilayer ceramic) between the +V and -V, the sound becomes very tight and the airy sound stage disappeared. Please comment: -

1. Am I using the correct type/value of PSU bypass caps?
2. I do not find much difference by desoldering all PSU bypass caps. Does it mean I can just leave them?

Thanks

Sunny

[carlmart]

Ceramics are not very good sounding in audio applications. Perhaps you should try different types, like stacked film or polypropylenes. Only some specific SMD ceramics seem to work well in certain circuits, particularlty digital.

You are proceeding as you should: trying and listening. If you don't like the sound of something why use it?

Some electrolytics, like Black Gates, seem to dislike bypassing.

A rule that seemed to work sometimes was to use several byapasses, equivalent to 10%, 1%, etc of original value. So if your main cap was 39uF, then you would add 3.9uF, .39uF, .039uF and 0039uF. All film, of course.


Carlos

[jackinnj]

Originally posted by carlmart
Ceramics are not very good sounding in audio applications. Perhaps you should try different types, like stacked film or polypropylenes. Only some specific SMD ceramics seem to work well in certain circuits, particularlty digital.

You are proceeding as you should: trying and listening. If you don't like the sound of something why use it?

Some electrolytics, like Black Gates, seem to dislike bypassing.

A rule that seemed to work sometimes was to use several byapasses, equivalent to 10%, 1%, etc of original value. So if your main cap was 39uF, then you would add 3.9uF, .39uF, .039uF and 0039uF. All film, of course.


Carlos

Avoiding bypass caps in a high gain circuit like a chipamp is dubious. The "airiness" which may have been heard previously could have been noise! A chipamp's feet should be stapled to the floor ! The point of the bypass caps across the electrolytics is to reduce the impedance at RF.

Ceramics aren't a good idea in the direct audio path, but they work here. One potential problem to note, however, is that you can fracture an SMT ceramic when soldering, or with an over-voltage situation.

Bypass caps may or may not be a good idea in some audio circuits -- I believe that Jung wrote in Audio Amateur that using an abundance of bypass caps AND the Super Regs could result in oscillation.