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Cathode bypass

Posted: Mon Jan 13, 2025 6:40 am
by griff
I'm gonna mod my Jet City 20watt to Jake E Lee/JCM800 specs. I've been watching Jason Tongs tutorial on him doing this to an old 2204 and I've been penciling in the relative components I need to do on the Jet City schematic.
Jason likes to bypass the second triode cold clipper with an electrolytic cap and also the fat cap is electrolytic. He said he prefers the sound. Apparently Friedman does the same.

What differences sonically can I expect between electrolytic and film in bypass positions?
What are you preferred caps for bypass positions on higher gain marshall style amps?

Re: Cathode bypass

Posted: Mon Jan 13, 2025 6:45 am
by sizzlingbadger
What differences sonically can I expect between electrolytic and film in bypass positions? None
What are you preferred caps for bypass positions on higher gain marshall style amps? Any high quality cap with a voltage rated high enough, I tend to prefer non Electrolytic where possible due to Electrolytic having a shorter working life.

Re: Cathode bypass

Posted: Mon Jan 13, 2025 6:58 am
by NippleWrestler
No difference at all. Considering there's only about 5v on the cathode you don't need much, even a ceramic would do it.

I like a 1k5/1uf combo on my cathodes.

But, friends don't let friends cathode bypass the cold clipper.

Re: Cathode bypass

Posted: Mon Jan 13, 2025 7:20 am
by griff
NippleWrestler wrote: Mon Jan 13, 2025 6:58 am But, friends don't let friends cathode bypass the cold clipper.
Shit, now I'm gonna have to get out the alligator clips..

Re: Cathode bypass

Posted: Mon Jan 13, 2025 7:27 am
by NippleWrestler
If I'm thinking of the right mods, he changed the 10k cold clipper to a 3k3, which isn't really a cold clipper anymore but just a straight up gain stage. It won't have the asymmetrical swing of the 10k (or 39k if you're Soldano or Mesa).

So bypass it all you want.

Re: Cathode bypass

Posted: Mon Jan 13, 2025 7:32 am
by griff
Yeah I'm a beginner but I understand the basics. Yeah 2.7k in that stage.
Kinda forget the technical side once you hear how good the amp sounds when he plays it.

Re: Cathode bypass

Posted: Mon Jan 13, 2025 7:42 am
by NippleWrestler
It's a good move to beef up the gain, and is an easy mod. I've never liked the stock 800 circuit - too bright, too thin, not enough gain. The 10k down to 2k7, 3k3, etc would add a bump in gain, but then would need a cap to finesse it otherwise it'd just flub out.

Soldano and Mesa can get away with a 39k cold clipper (which dumps 90+% of the signal) because there's 2 or 3 or 4 recovery stages afterwards. Not so in an 800 design.

If you've a 10k in there you can audition different resistors with a crocodile clip over it before you commit.

Re: Cathode bypass

Posted: Mon Jan 13, 2025 10:06 am
by FuzzMonkey
NippleWrestler wrote: Mon Jan 13, 2025 6:58 am But, friends don't let friends cathode bypass the cold clipper.
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