Amp modders... How do I smooth out the 1-wire mod?

[Vrad]

Yes, correct. You could also try a 1.5K/4.7uF V1A and up the grid resistor to 150K

Steve

egnater seminar?

Hey - it sounds good! Very smooth gain...

Steve

Steve you're referring to the 100K plate resistors?

Yeah, sorry - V1A plate resistor. Leave V1B at 100K...

Steve

I see and that changes the bias on the tube?

It is changing the gain of that stage. A higher value will increase the plate voltage drops/rises (depending on the polarity of the input signal). V=IxR, right? After the coupling cap (which blocks DC), you have bigger swings in AC voltage with a higher resistance value and thus, you have higher gain.

The cathode R/C is a tuned circuit changing the frequency at which gain is increased and also increases gain.

Steve

I see.... So the R/C is where you set up what freq's get boosted then the coupling caps add gain on top of what's already boosted.

No, the cathode R/C adds gain with the cap to ground as well as says what frequencies get added gain (anything above the "rolloff frequency" gets the added gain - you can calculate that frequency like this: F = 1/(2pi)RC, where pi = 3.14xxxxx). The coupling caps don't add gain, they block DC. The plate resistor adds gain and the coupling caps block DC.

See what I'm saying? Both the plate resistor and the cathode cap in a gain stage add gain. You can't just randomly raise the plate resistor value either. You have to adjust the cathode resistor as well to provide the bias to the stage.

Steve

Yeah I got you. That was actually something I was going to ask you... if there was a dependency on the cathode resistor/bias resistor...

I saw that formula on the Metroamp site. Its very handy for figuring out the frequency...

I got 810/10uf on the V1A
2.7k/.47uf on the V1B... Sounds good too. Smoother