Simpler Fader/booster circuit schematic

Hello, friends,

I'm in need of a simple fader/booster schematic that utilizes something like an INA137 or some other high performance DIP8 IC for use in a preamp/mixer design. I could just use an attenuator which would be simpler, but for educational and design purposes an actual fader that goes from -100(muted) to +6. I used one of the schematics on the data sheet for the INA137 to build some -6 unbalancing circuits, but didn't know if there was a way to simply use a variable resistor to create the desired cutting/boosting I am after. I can follow a schematic pretty good but when it comes to understanding what is actually going an designing circuits I'm a bit out of my depth. Any help or pointing in the right direction would be very much appreciated. I'm trying to keep the whole circuit as small as possible as case all the other parts are going in is filling up very quickly.

Thanks!

Paul

All you need is a simple "non-inverting" one op amp gain stage...  post fader gain stages generally provide +10dB (3x) voltage gain. 

Using 4 resistors instead of just two you can provide a differential reference between two different local grounds.

JR

Thanks! That should get me started. At least now I know more specifically where to focuse my searches.

Thanks!

Paul

  Just to clarify, JR is probably proposing to reference the ground of that amp from a 4th wire coming directly from the fader ground, to improve maximum attenuation.

JS

I plan on using a rotary switch for the fader. I'll have to reference a stepped log calculator.

Thanks!

Paul

joaquins said:

  Just to clarify, JR is probably proposing to reference the ground of that amp from a 4th wire coming directly from the fader ground, to improve maximum attenuation.

JS

Click to expand...

It not only improves fader kill (a concern in high performance console design) but it references the audio path between the sending local audio ground and the destination audio ground. It is a mistake to ASSume that audio ground is 0V everywhere (especially if the fader is physically located some distance away from the circuitry.)

JR
JR