have problem with tone control

[Ahmad_tbp]

hi ...
i built the tone control that marshall uses in bass and guitar amp ... ( http://users.chariot.net.au/~gmarts/ampbasic.htm )
and used a jfet buffer before it ...
infact i wanted to build a tone control effect pedal , i plugged my bass right into the buffer and then tone control circuit .... but the sound decreased too much and almost dead , and nothin change so much when i turn the knobs ...
so should i use a pre amp ? or the problem s not cuz of i don usin a preamp ?

 

[anatech]

Hi Ahmad_tbp,
The tone circuit is designed to work at line levels. You need to provide gain as a tone control circuit can only drop the signal level. I would expect you to get increased noise doing this.

Can you post the schematic of your buffer?

-Chris

 

[Ahmad_tbp]

here s : http://www.generalguitargadgets.com/diagrams/buffer_jfet_sc.gif

 

[anatech]

Hi Ahmad_tbp,
Okay, the buffer is close to unity gain. You need to have at least as much gain in the buffer as you lose in the network. You need a quiet buffer / amplifier stage to work at those levels. Think dynamic mic level quiet.

-Chris

 

[Ahmad_tbp]

hi Chris 😉
i need a mic preamp befor buffer ?

 

[anatech]

Hi Ahmad,
A preamp would be the buffer. If you design it to just compensate for the loss, you can plug it into the same input. This tone stack is intended to go after amplification and mixing of channels. You may be trading some noise for external tone controls.

-Chris