Anyways, what i'm talking about is this....say you have a 820R on a 12ax7 gain stage bypassed with a 1UF and you like the tone you're getting but want less gain. If you doubled the resistor size you'll drop some gain but you will also get more effect from the bypass making the tone brighter or thinner. So what if you double the resistor to 1.6k then add a 820R in series with the cap? will you then get the same ratio of brightening as you did before, so less gain w/o changing the tone? Or does it not work in a linear fashion like that?Cathode bypass question
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iknowjohnny
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Cathode bypass question
It would seem to me this would work the way i want, but i never take it for granted that because it makes sense to me it'll work that way ! Anyways, what i'm talking about is this....say you have a 820R on a 12ax7 gain stage bypassed with a 1UF and you like the tone you're getting but want less gain. If you doubled the resistor size you'll drop some gain but you will also get more effect from the bypass making the tone brighter or thinner. So what if you double the resistor to 1.6k then add a 820R in series with the cap? will you then get the same ratio of brightening as you did before, so less gain w/o changing the tone? Or does it not work in a linear fashion like that?
Anyways, what i'm talking about is this....say you have a 820R on a 12ax7 gain stage bypassed with a 1UF and you like the tone you're getting but want less gain. If you doubled the resistor size you'll drop some gain but you will also get more effect from the bypass making the tone brighter or thinner. So what if you double the resistor to 1.6k then add a 820R in series with the cap? will you then get the same ratio of brightening as you did before, so less gain w/o changing the tone? Or does it not work in a linear fashion like that?Re: Cathode bypass question
The resistor and capacitor form a parallel RC filter. If you scale the resistor by 2, then halve the cap by 2 to give the same frequency response.
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iknowjohnny
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Re: Cathode bypass question
Soto replicate 820R/1uf but with less overall gain i'd use 1.5k/.47uf?
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iknowjohnny
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Re: Cathode bypass question
Why, thank ya ma'mm
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Super_Reverb
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Re: Cathode bypass question
IMO, if you're happy with the gain, leave the cathode circuit unchanged. Many designs add a series resistor after the coupling cap, to form a voltage divider, when feeding a volume pot.
Another way to dump some gain is to split the plate load resistor: that is, connect two plate resistors in series, keeping series total the same approximate resistance. For example, if you placed two 50Ks in series and tapped the output off the middle, you'd have about half the plate swing relative to gnd (remember power supply = AC gnd), but you would maintain a similar plate DC operating point (Plate voltage plays a role in your tone as well).
rob
Another way to dump some gain is to split the plate load resistor: that is, connect two plate resistors in series, keeping series total the same approximate resistance. For example, if you placed two 50Ks in series and tapped the output off the middle, you'd have about half the plate swing relative to gnd (remember power supply = AC gnd), but you would maintain a similar plate DC operating point (Plate voltage plays a role in your tone as well).
rob
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iknowjohnny
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Re: Cathode bypass question
Yeah, i've done all that. But i'm not so much in need of dumping gain as i just like the sound of gain stages with 1.5k cathode resistors more than the 820R thats there now which i only used because i was emulating the stage b4 a marshall's CF.