buffer impedance and power debate

[aortizjr]

So I have been working on a guitar buffer, unity gain, to probably go before and/or after my pedals.

Now I have the Craig Anderton book on Projects for Guitarists. It has an IC based one that uses a bi-polar (+9 - 9) supply and receives no power on the audio path input. It also converts the output impedance to a lower impedance.  Here is modified idea sketch.



Now looking at say the superbuffer:

http://www.muzique.com/lab/superbuff.htm

You have the input and output at really high impedances, and basically just putting some power behind it. Also they typically have power on the input line and run it with just a +9 and ground.

So which is better, and under what conditions? I have built the Anderton one, and just used a charge pump to get the bi-polar supply.

The Anderton one is pretty nice and you can definitely tell a difference just using a TL071. To me it sounds just like using a really short cable.

I have no experience with any of the others. From reading around here and several other places, the reviews seem mixed.

[The Tone God]

What is input 2 about ? Are you trying to mix signals ? Signals from the guitar ? Then that is not going to work. When you turn one guitar down you will ground out both signals. You are better off to use an active mixer circuit.

As I doubt you will ever use a signal that swings the full voltage rage you would be better off just converting the circuit to single supply so you can get rid of the charge pump sillyness.

Opamp-eration

Which is "better" depends on what you need. If all you need is a simple mixer and/or boasters check the ICs datasheet as there should be some schematics for those functions.

Andrew

[niftydog]

I think by "power" you mean current drive, yes?

That seems to me what the superbuffer is all about; This is intended to drive long cable runs. While they do mention it being used prior to pedals they make the distinction of true bypass pedals, which when bypassed essentially appear as long cable runs. Still, I can't see why you couldn't get the best of both worlds and drop the value of R7 a bit.

I think using the term buffer when talking about a line driver is a misnomer. A line driver is a line driver, not a buffer. So, IMO the superbuffer is in fact a line driver - and a bit OTT too! Lets face it, a 20ft guitar cable is hardly long is it?

Use a vanilla buffer and be done with it - unless your amp is in the next county!