Champ 5C1 mods

[armillary]

I'm building my second 5C1, using the Fender schematic and layout diagram, but using a different chassis arrangement (it's what I have laying around). I'm pretty happy with the first one.

I'll build it to the schematic and makes sure it works, but then I'm thinking of substituting some of the component values, and wondering what ideas others have. The goal being to overdrive the 6SJ7 a little more. For example:

Dropping the 75K ohm input resistor to a lower value to attenuate the input signal less.

Or dropping the 5M ohm grid lead resistor to a lower value to allow the bias to bleed off faster.

Or dropping the .02 uf grid capacitor to a lower value so it holds less bias charge.

Or your suggestions?

Thanks in advance.

[Stevem]

In my book its very hard to get good distortion with even two preamp stages, no less one like your 5C1 has!
For me good distortion comes from having the wave form clipped on both the top and bottom before it hits the output tube and there is no way to get that with just that one pentode preamp stage.
Even with that latter blackface champs you only have two preamp stages before the output, so if your guitars pickup`s do not have tons of output all you get from the preamp section is the second gain stage clipping in a good way on one end of the wave form, and then the output tube clipping on the other end but in a different way since it has less gain if you will.
You want the clipping to be had from the tube saturating more than cutting off and the only way to get that is by having two preamp gain stages saturating on opposite halfs of the wave form.

In short the only way even with these latter champs that use two preamp sections the only way, 95% of the time to get what I call good distortion is to place a clean drive stomp box in front of the amp so you can clip that first gain stage when you want.

Changing componet values will have some effect, but not as much as you will probibly want, in fact the most change in the amps preamp section other than bass responce from bigger cathode or bypass caps will come from dropping the voltage to the preamp.
Thats my 2 cents.

[jjman]

The 75k is dropping the signal only 1.5% since the grid leak value is huge. I have a Silvertone with similar setup and I'm resigned to using a boost for significant overdrive potential. My only thought was to increase the cathode resistor of the output tube to trigger cold clipping. But the output would be lower too from that.

[armillary]

Many thanks to you both for your replies. Maybe I'll try to get a little more bass out of it by bumping the coupling cap to .05uf, get a boost pedal and enjoy it for what it is.

[armillary]

I just found the schematic for the 5C2 Princeton. It looks interesting. I think I'll try that this time.