Basic buffers other than at AMZ???

[BillyJ]

Was curious if there are more of these designs around?
I am interested in mostly IC based buffering but FET is cool too.
I did some searching but most stuff I found was for use in hi-fi stereos and such...not sure if those would be any good.

[R.G.]

It's hard to step on circuits anywhere without stepping on a buffer. Cookbooks are full of them. What did you particularly have in mind?

[BillyJ]

Something using a OPA2604AP because I have a couple....
Or something like it.  5532 perhaps???
I want unity with zero noise or at least as little as possible.
Basicaly I was thinking if I had a really clean transparent buffer I could put it first in my chain and just leave it on effects running or not.
Mostly to drive a long cable when I have no effects running which belive it or not is most of the time...All those pedals just sitting there seem to roll off a lot of the highs....

[R.G.]

Basicaly I was thinking if I had a really clean transparent buffer I could put it first in my chain and just leave it on effects running or not.
Mostly to drive a long cable when I have no effects running which belive it or not is most of the time...All those pedals just sitting there seem to roll off a lot of the highs....

Good observation, good motivation. I think the long cables are what rolls off your treble. Even good coax cable has a capacitance of about 10-30pF per foot. A ten foot cable will give you 100-300pF and treble rolloff.

For a gain-of-one, just hook up the opamp (that's what you got) so that it's powered from +9v and ground, and hook the output to the inverting (-) input. Make a bias voltage supply from two resistors across the +9V/0V power supply of about 10K, and bypass the junction of these two resistors to ground with at least 1uF of capacitance. Connect a 2.2M resistor from this same junction to the + input of the opamp. Connect a 0.1uF mylar capacitor from your input to the (+) input of the opamp, and a 2.2M to ground at the input side of the capacitor as a pulldown. Connect a 1uF capacitor, + side to the output of the opamp, (-) side to a 1M to ground. The output is from the junction of the (-) side of the output cap and the 1M to ground.

You'll have to look up the proper pin numbers, but those are the right functions. This setup gets you a 1M input resistance and very low output resistance, suitable for driving a LOT of loading.

Yell with questions.

[petemoore]

Is buffer distortion sometimes intentionally created and used?

[Peter Snowberg]

Absolutely. It's just another case of overdrive. The 'typical' opamp unity gain buffer doesn't sound wonderful when overdriven (it's a broad generalization, bear with me). Most boosters are transistor gain stages. Some of these are JFET and sound pretty nice when overdriven.

Zvex sells the super duper 2-in-1 which is two buffers in series. The first overdrives the second for fuzz.

-Peter

[petemoore]

On a [S or not so simple buffer?]
 Are certain types of transistors or opamps better choices than others for buffers with gain?

[bwanasonic]

Basicaly I was thinking if I had a really clean transparent buffer I could put it first in my chain and just leave it on effects running or not.
Mostly to drive a long cable when I have no effects running which belive it or not is most of the time...All those pedals just sitting there seem to roll off a lot of the highs....

I know the thread is *other than AMZ*, and you mentioned a preference for IC based designs, but I really like Jack Orman's MOSFET Booster/buffer circuit.  A lot.  For the intended purpose you mentioned it is just about perfect. I'd give it a try given it's simplicity.  I'd be interested in any circuit that is *better* for this purpose.

Kerry M

[Tubefreak]

Hi RG,

what would you do to make the output impedance 600 Ohm. Let's say with a standard TL072.

Kind regards,
Maarten

[Peter Snowberg]

what would you do to make the output impedance 600 Ohm. Let's say with a standard TL072.

One way would be to just use a NE5532 instead if you don't need the JFET inputs. They'll drive 600 ohms directly. I feel TL072s are better for input and NE5532s are better for output.

That's one way to go.

-Peter

[bettycat]

Hmmm, I use a homemade OpAmp buffer in front of my true-bypass-strip, based on Jack Orman´s design, but slightly modified to get a lower impedance. Very good effect, no noise and absolutely no tone coloration. You can download the project paper for this buffer at my DIY True Bypass Strip webpage. Click at the link in my sig and scroll down to the FAQ. there you will find the complete description.

[petemoore]

Is like stepping stones, but you could just about cross the Missippi in a wide spot with them.
 I've never run more than 8 pedals at a time, of course that was before I knew abour buffers and boosters.
 I use a 'two main sections' system, with Booosters, Fuzzesm and 'twisters' [like Wah, Ottowah, etc] then cable that to near the amp where the Boss chorus, and reverb/echo, the second section stays on and preset for the most part, though I could use another echo [on the floor for long [say for like watchtower slide lead for ex.].
 this way it keeps the floor neater and I can to the finicky] presets on the chorus Rev/echo much easier that way.

[Tubefreak]

Hmmm, I use a homemade OpAmp buffer in front of my true-bypass-strip, based on Jack Orman´s design, but slightly modified to get a lower impedance. Very good effect, no noise and absolutely no tone coloration. You can download the project paper for this buffer at my DIY True Bypass Strip webpage. Click at the link in my sig and scroll down to the FAQ. there you will find the complete description.

Which mods did you do to it?

Maarten

[bettycat]

Hmmm, I use a homemade OpAmp buffer in front of my true-bypass-strip, based on Jack Orman´s design, but slightly modified to get a lower impedance. Very good effect, no noise and absolutely no tone coloration. You can download the project paper for this buffer at my DIY True Bypass Strip webpage. Click at the link in my sig and scroll down to the FAQ. there you will find the complete description.

Which mods did you do to it?

Maarten

As written in the the project paper the two 1M resistors were changed to 2M to get a 1M inout impedance instead of the 500k of the original design. As stated before, it´s only a slight modification, but useful.