The design is getting pretty well defined. It is a two channel acoustic guitar amp, so it is more of a personal PA system than a basic electric guitar amp. Each channel has its own volume and tone controls. There is a master volume before the phase inverter.
The two channels of the preamp have the same basic structure:
Input ---> pentode gain stage ---> triode cathode follower ---> tone stack ---> triode gain -->
The outputs of the two final triode gain stages are mixed and then go into the phase inverter.
The volume pot for each channel can fit either before the cathode follower or at the end of the tone stack. Both places work equally fine numerically for frequency response, headroom, and overall gain. DC is blocked in both places.
Nominally the volume pot will be set at about 20% of max resistance and is a 1Meg pot. If the pot is before the tone stack, the voltage at the output of the cathode follower feeding the tone stack will be about 7 vrms. If the pot is after the tone stack then the voltage feeding the tone stack will be about 33 vrms.
The question then is if it is better to run a larger signal through the tone stack and then attenuate it, or is it better to attenuate it first? Is noise a consideration one way or the other?
The two channels of the preamp have the same basic structure:
Input ---> pentode gain stage ---> triode cathode follower ---> tone stack ---> triode gain -->
The outputs of the two final triode gain stages are mixed and then go into the phase inverter.
The volume pot for each channel can fit either before the cathode follower or at the end of the tone stack. Both places work equally fine numerically for frequency response, headroom, and overall gain. DC is blocked in both places.
Nominally the volume pot will be set at about 20% of max resistance and is a 1Meg pot. If the pot is before the tone stack, the voltage at the output of the cathode follower feeding the tone stack will be about 7 vrms. If the pot is after the tone stack then the voltage feeding the tone stack will be about 33 vrms.
The question then is if it is better to run a larger signal through the tone stack and then attenuate it, or is it better to attenuate it first? Is noise a consideration one way or the other?