This shouldn't be that hard (should it?)

[Ripthorn]

So I am trying to implement a solution to reduce the volume drop of a tone stack, but I can't seem to get anything working.  I have several builds under my belt, but there has to be something I am overlooking.  I first tried the JFET buffer at jack orman's site, but I got now volume out.  I figured I must have just done something stupid, tried again and still nothing.  So I decide to try the opamp buffer (which is actually what I would like anyway, I discovered).  I have it set up as self-biasing (i.e. voltage divider as opposed to two separate supply voltages) with 2.7M resistors (1.35M input impedance).  I am using one half of a TL072 with +12V supply.  Everything is connected properly, but it doesn't want to work for me.  I do have it set up to amplify (a voltage divider in the feedback loop) with a trimmer to set the gain.

I guess my questions are thus:
Does the LM7812 (using for my power supply) require a minimum current in order to provide regulation?
What could I be missing?  It has to be something simple as the schematic is about the easiest thing to build.

I am open to any suggestions.

[Derringer]

have you tested the new buffer(s) outside you build?

I would do that first and make sure they are working properly.
Then, make sure your other build is working as it has been (volume loss through tone stack)
Make the process as simple as possible for subbing the working buffer into the existing circuit (is this in a breadboard? things soldered yet?)

then see from there

give it time, it'll come together

[ayayay!]

A buffer isn't going to recover volume loss, just perceived frequency loss.  (Notice how buffer pedals, or buffers built into pedals for that matter, lack volume controls    )

You need a recovery stage.  Say, something like the Ibanez SD9 for example.  It has to use 1/2 of an opamp after the BMP tone stack. 

[Thomeeque]

So I am trying to implement a solution to reduce the volume drop of a tone stack, but I can't seem to get anything working.  I have several builds under my belt, but there has to be something I am overlooking.  I first tried the JFET buffer at jack orman's site, but I got now volume out.  I figured I must have just done something stupid, tried again and still nothing.  So I decide to try the opamp buffer (which is actually what I would like anyway, I discovered).  I have it set up as self-biasing (i.e. voltage divider as opposed to two separate supply voltages) with 2.7M resistors (1.35M input impedance).  I am using one half of a TL072 with +12V supply.  Everything is connected properly, but it doesn't want to work for me.  I do have it set up to amplify (a voltage divider in the feedback loop) with a trimmer to set the gain.

I guess my questions are thus:
Does the LM7812 (using for my power supply) require a minimum current in order to provide regulation?
What could I be missing?  It has to be something simple as the schematic is about the easiest thing to build.

I am open to any suggestions.

It would be much easier to help, if you would provide schematic of your circuit to us - there's lot of information missing in your description..

So just one wild guess, is that voltage divider in the feedback loop "grounded" to Vcc/2 as well? Or "grounded" to gnd via capacitor? If not (if grounded directly to gnd), that may be your bug.

T.

[Ice-9]

Are you using the two 2.7 Mohm resistors as the votage divider for the bias supply for the opamp, if so this value may be to high as the current available to the opamp may be too low. Try using two 10k resistors as the voltage divider for the opamp. You can always get the impedance by using the value resistor you require from the opamp input to ground

[Ripthorn]

Okay, so I had a couple minutes to fool with this.  Turns out if I turn the trimmer so that it's value is zero, it works like a unity gain buffer (since R2=0 and gain=1+R2/R1).  I guess I am curious as to why this isn't working with the trimmer in there (trimmer set up as variable resistor).  I will try to draw up a schematic of what I have as soon as I can.