The best value bypass cap on a champ style amp.

[roberto]

I think you won't notice any difference going down to 4µ7, anyway two switchable values (like 22µ and maybe 680n) could be a good idea.

[Super_Reverb]

Like the other guys suggested - if you want a specific feel, try something in the 0.47u to 22uF range. 22uF across a 1500 Ohm cathode resistor creates a low frequency corner at ~ 5 Hz. It's not likely that your guitar amp has flat response down to 5 Hz.

For me personally, I'll plug in a value and then play through a number of volume and tone settings to see if it works. If you like an overdriven tone, chances are you'll get better results with a smaller value. Overdriven bass notes can muddy your mojo.

Tweaking this capacitor value will only have a significant effect if it creates a dominant pole, that is, if it is the lowest pole in the bass response. Coupling caps are also part of the equation.


rob

[jdw3]

I initially had no cap on my tweed champ I just built. It needed one. So I installled a 4.7uf. It has great gain but a little muddy. I'm using the 1.5K resistor.

For less mud at top volume, if I went down to 1uf or less, would the resistor have to be increased? I know there is a relationship there and and I don't have the cap/res site here.

I was thinking such as; 2.7K/.68uf for example. How would that sound in a tweed champ?

[Leo_Gnardo]

oh sorry. V1 cathode bypass cap on a champ

Thanks for alleviating the cornfusion. Nonetheless it's a good idea to up the voltage on the output cathode bypass cap, as there's often 25V or more there even at idle. Put in a 50V rated cap & you'll have a hard time wrecking it unless your output tube goes short-circuit. While you're at it bend the leads on the new cap so there's some distance between it and the cathode resistor. So ya don't bake it.

[roberto]

I was thinking such as; 2.7K/.68uf for example. How would that sound in a tweed champ?

Less fat, less gain and an enhanced bright effect.

[jdw3]

I was thinking such as; 2.7K/.68uf for example. How would that sound in a tweed champ?

Less fat, less gain and an enhanced bright effect.

Are you saying less gain because of the 2.7K?

Would a .68uf cap well with the 1.5K? Just wondering about the "knee" or cutoff of the combination. I don't want to lose any gain. I suppose the only way is to solder them in.