AMZ Super Buffer

[Rebel420]

Has anyone built the AMZ Super Buffer?   I know the parallel  Opamps gives a stong current drive, with no voltage gain (I know I could tweak to give gain)... but how is the headroom affected by using parallel opamp stages? is it the same as with a single opamp, or is theremore headroom available? or is there less for some reason?  I am ASSUMING there should be more headroom, but not sure... I know it wouldnt be hard to whip one up, but with no scope, hard to get a quantitative answer.  Any takers on this one?

[R.G.]

There is no more headroom; "headroom" as it's commonly used is the difference between the normal max signal and the max max signal before things get ugly. The max max signal is dictated by the power supply voltage in voltage based system - like audio. No more headroom.

There is a point of diminishing returns on most things. By the time you get one opamp to buffer a signal, you're usually well past that. Adding more current capability is only useful under some limited sets of situations - really, truly long cables with high capacitance, for instance, or perverse loads. Generally, something like a single LM833 is all you'll ever need.

[Rebel420]

Thank you for the fast response.  I knew that the voltage rails are what determined headroom, relatively speaking, however, with the second opamp in parallel, I was thinking (secretly hoping?) that the multiple stages were splitting the load so to speak,  and effectively doubling the headroom. 
    Basically, I'm looking for a buffer to squeeze into a slimline volume pedal, to buffer the signal for pedal steel, which has a much higher output than a guitar pickup, so a 9v supply is a must, as is long battery life... So I'm thinking I will go back to a single stage buffer,  and if need be, slighly attenuate the signal BEFORE the buffer, and let the opamp recover some gain.

[zyxwyvu]

Thank you for the fast response.  I knew that the voltage rails are what determined headroom, relatively speaking, however, with the second opamp in parallel, I was thinking (secretly hoping?) that the multiple stages were splitting the load so to speak,  and effectively doubling the headroom. 
    Basically, I'm looking for a buffer to squeeze into a slimline volume pedal, to buffer the signal for pedal steel, which has a much higher output than a guitar pickup, so a 9v supply is a must, as is long battery life... So I'm thinking I will go back to a single stage buffer,  and if need be, slighly attenuate the signal BEFORE the buffer, and let the opamp recover some gain.

Attenuating the signal and then adding gain will not give you any more headroom. The easiest way to get more headroom is to increase your supply voltage. You can do that by adding another battery in series, or doubling/inverting the voltage with a MAX1044.

[R.G.]

With the limits you're setting, you could either
(a) use a rail-to-rail output opamp and recover about 2-3V; normal opamps can't go all the way to the power rails
(b) as mentioned, use a charge pump converter to give you more power supply voltage
(c) use 12V camera batteries to get a few more volts.