Input Stage/Boost Idea

[Bill Mountain]

I am working on a design that splits the signal after an input stage.  I will not be using this particular set up but I thought it would be fun to experiment with something like this:



Each pot could be used (externally or as a trim) to adjust the output level of each signal required for the following stages.

I will be using the low gain side (with fixed resistors) for a clean channel and the high gain side for a fuzz channel.  Then I plan to mix them together down the line.

I haven't tried this but I'm pretty sure it would work.  It should work on different active devices as well (tube,Si NPN, MOSFET, Etc.)  It may not be extremely functional but I think I can use it during R&D to get the best output levels for my two channels.

Thoughts?  Criticisms?  Better ideas?

[GibsonGM]

Hi Bill,

Not a bad idea to play with or anything, and you could certainly experiment with the concept and see what you get!  Don't forget your blocking caps ;o)   One thought is what output impedance you'd have with that arrangement?   You typically take the output from the source when splitting or buffering, and from the drain when boosting due to this...it's a current vs. voltage thing....you're not so interested in voltage but current when splitting or buffering...a good tutorial will explain the principles behind this.

I like to do what they've done over here at AMZ:  http://www.muzique.com/lab/splitter.htm

The JFET is 'optimized' this way to give you a low output impedance for whatever follows it.  It would be a piece of cake to adjust output levels for 'Low' and 'High', too!   Keep experimenting and you'll come up with some great stuff!

[Bill Mountain]

All good thoughts.  Many things are assumed with this quick sketch.  One assumption is that the next stages will be not loading down the outputs.  I had originally used a buffer but I realized that I would need an additional gain stage to get my fuzz side to work better.  I also would need to invert the "clean side" to mix without having phase issues (if I added a discrete boost to the fuzz side).  A few opamps would solve all of these problems but I'm trying to go without them as a challenge (and to force creativity).  I think a fun output volume boost mod is to tap the drain resistor at a few places and switch between them.  This is an extension on that idea.

[GibsonGM]

Nothin' wrong with that!  There's more than one way to skin a cat ;o)