Cathode bypass cap rolling, a worthwhile experiment!

[Tom-s]

The cathode bypass capacitor has a big influence on the sound of my system.

I've experimented with caps i had on hand from other projects.

I can really recommend experiencing the effects for yourself. There's room for improvement with the cathode bypass cap.

Bottlehead made it really accessible in the SII. I've attached flying leads internally so it's easy to switch out caps every few days.

Beware there's about 50V potential, so there's a shock hazard!

What was tried.

220uf, 100V Elna Cerafine (was my "stock"/start point) electrolytic
30uf, 60uf MBGO 160v Russian "oil" capacitors / bathtubs (will try with 90uf and/or 120uf in the future).
30uf, 60uf Amp Ohm polypropylene film 630V

Any combination of the above. In picture you see the 30uf film cap and behind the 220uf Cerafine with 60uf MBGO being compared.

How does the cathode bypass cap influence the sound? From my experience, the layering in the music changes with the caps. The other things that stands out is the tonal balance, details and decay.

Elna Cerafine (i think this is a cheap version, not a real one, don't know) is a fine electrolytic. Unfortunately i can't comment how it compares to stock.

With the Ruskies the soundstage somewhat collapsed and bass left to be desired. Not recommended.

The film caps were a clear winner in this test. I'm not sure yet if the bigger is better.

With a combination, the effects changed, not always for the better. However I do prefer Elna + MBGO over Elna or MBGO.

[Deke609]

Cool! I'm very interested. Keep us posted.

I thought there was an audible improvement when I replaced the Kaiju stock 160 uF 'lytic with a Solen MKP of equal size. In the rebuild, I've installed a 330 uF Solen, but can't comment on the effect of the increased capacitance b/c (1) other parts have changed as well (OPTs), and (2) I really can;t remember how the Kaiju exactly sounded with 160 uF film caps before I dismantled it a month ago.  So I'm eager to hear your impressions of the effect, if any, of increasing/descreasing capacitance.

Edit: another thought: Are the caps already broken in? If not, I wonder whether a mere 50V applied to the caps will mean an extended break in period?

cheers, Derek

[Tom-s]

Thanks for inspiring me Derek! Your builds are a great example.

I'm wanting to believe it makes a difference but i'm not convinced yet. Still i find myself using 2x30uf film caps more often than the 30uf films. Since these aren't going to fit unless the SII grows a bit; the search for a 50uf-100uf polypropylene / oil cap has begun.

Don't know much about burn-in with capacitors. Have to admit i'm not that good in burning-in caps or tubes anyway. The caps are rotated on a daily basis, as are the tubes. For me it's more about the general sound of my system over it sounding good with only one tube type. So a cap has to do well with most/all of my preferred combinations.

[Paul Birkeland]

The caps are rotated on a daily basis, as are the tubes.

Daily tube rolling destroys sockets pretty quickly.  I would strongly recommend picking the tubes that you like the best and using those. 

[Deke609]

I think that would kill 90% of the fun for Tom-s.    IIRC, he has an impressive collection of tubes.  Perhaps a yearly or every second year tube socket replacement!

cheers, Derek

[2wo]

You can get motor run caps to about 100uf or so to try, they are poly/oil and not real expensive.  Big though ..John

[lordvader]

Quick question about the bypass cap -
The one that comes in the kit is rated at 250V - but you say there's only a 50V potential across the cap?

[Paul Birkeland]

Quick question about the bypass cap -
The one that comes in the kit is rated at 250V - but you say there's only a 50V potential across the cap?

The tough part here is that if you plug the tube in with the fat pins not in the fat socket holes, the potential across the cap will be a lot more than 50V!  The 250V cap we provide will be a little more durable and more likely to blow the fuse than a 63V rated capacitor that might otherwise do the same job.