Bypass Caps

[SteveS-1]

Hi folks,
Looking at the previous post of the Rev C/D? board using bypass caps on the electrolytics I am inspired to ask this question.

I have a rev B version - which instead of 4 120uF Electrolytic caps has 8 220uF caps. I had though about replacing them with something fancier, but I wonder if just putting some bypass caps on the reverse side of the board might be a better idea.

Using the 10% rule of thumb, I should probably use 22uF caps to bypass them with.

My questions are - 1. Is this worthwhile? 2. Can I use a smaller bypass cap - say 1.0uF? and finally what significance is the difference between the 2 version with respect to these caps (8x220uf vs 4x120uF).

Thanks SteveS (who is getting punted by my attempt to login as SteveS with my usual password).

[Shannon Parks]

My questions are - 1. Is this worthwhile? 2. Can I use a smaller bypass cap - say 1.0uF? and finally what significance is the difference between the 2 version with respect to these caps (8x220uf vs 4x120uF).

Personally, I haven't trekked down the tweaking my power supply route yet, but see no harm in experimenting at all (minding max voltage ratings). FWIW, I think the electrical capabilities (ESR, capacitance, etc) of modern electrolytics blow away the electrolytics of old used in the old Dynaco's and Eico's. That said, I took some data on a 100% stock ST70 and tried some different/fancy caps at the B+ filtering stage. I figured I see <some> change, like the noise floor dropping or a bass boost, but nothing happened. So I'm just focusing on getting a matched quad of EL34's at this point - all my test Sovteks were trashed. I've gotta quit skimping on tubes.

I haven't done a side-by-side comparison, but there's no real performance difference between the old style power supply and the new.

Thanks SteveS (who is getting punted by my attempt to login as SteveS with my usual password).

If you still have problems logging in, email me at mod@diytube.com and I'll fix you up. I hope to upgrade the forum software to a less buggy version sometime this summer.

Shannon

[erichayes]

Hi All,

As Shannon points out, electrolytic capacitor technology has come a long, long way in the last 30 years. The 10% rule has pretty much been obsoleted unless you're using NOS caps, and even then it's overkill. My experience with my amps and Bud Wyatt's and Bob Neil's ears (they can tell you what the dielectric material is in a coupling cap by listening to it... frightening) is 0.27µF Solen Fast Caps thrown across all the filters does improve the sonic performance, but only if the rest of the system (source and speakers) is capable of reflecting the improvement.

I say, knock yourself out--that's what DIYing is all about.

[SteveS-1]

thanks for the replies,

I'm doing some mods on my preamp, and thought I would order some extra parts for an upgrade to the ST-35.

At this point I will probably do the following
- new gold rca jacks
- replace the orange drops with auricaps
- try some tube rolling to replace the Russian 6n1p's with probably some Electroharmonix or JJ Teslas.
- perhaps order enough Solen Fastcaps to bypass the electrolytics if they will fit in the chassis!

Stevo

[EWBrown]

A lot of the electrolytic caps designed for switching power supplies are of the low ESR type, which is just what the doctor ordered for our new tube projects. Any chance I have to get ahold of a dead or scrapped power supply, first thing I do is remove all the electrolytics, power resistors, "box" type caps, mylar caps, and ICLs, all of which will get re-incarnated into futire tube projects.

The "autoranging" supplies typically have 400-450VDC "bulk" caps, the 110/220 selectable types have 200-250V caps in the primary side. The low voltage caps are perfect as cathode bypass caps.

There's gold in that "trash"

/ed brown in NH