Just a quick question about buffer

[Agung Kurniawan]

Hi guys...
Which version of buffer that have smaller noise? Opamp or transistor?
Or maybe I should use the high spec semiconductor to get smaler noise?
Or maybe there is no noise at all cause of the gain its about unity?

[EBK]

I'd go with an op amp.

Power supply rejection ratio  .

[Agung Kurniawan]

Power supply rejection ratio  .

Well, I agree with that

[R.G.]

It's not possible to answer that question correctly with a single answer. Noise in active electronics is a highly complicated subject.

To get to a usable answer, you need to clearly specify the thing that is providing signal (guitar? another pedal? which one? all possible?) as well as what will be amplifying after the buffer, and how much gain that is.

Every conductor has thermal noise that can't be reduced. Active devices have several kinds of noise.

Playing the noise game successfully involves matching the design of the very first stage of amplification after the signal source to the bandwidth and source impedance (and frequency-related source impedance, if that changes) to the first amplification stage, and to the amount of gain in each following stage. The lowest noise is always obtained by using a suitable device for the source impedance and bandwidth, and by obtaining as much signal gain as possible in the first stage, because the first stage's noise is amplified by all following stages.

Obviously, if you start with a gain-of-one-buffer, you're violating the starting rule to begin with.

Then there's the issue of whether the buffer matters. In most guitar circuits, even mild attention to buffer design will make the buffer inaudible in the resulting noise.

This just goes on for pages.

The right answer is to do whichever circuit you can do moderately well, which usually says "use an opamp".  Beating a well-designed opamp AND a good design with that opamp will be tough to do, even using super-duper-unobtainable discrete semiconductors.

[bool]

...

Then there's the issue of whether the buffer matters. In most guitar circuits, even mild attention to buffer design will make the buffer inaudible in the resulting noise.

...

I'm going to disagree with that ... a little. High-gain circuits are very picky and there are certain counterintuitive scenarios when inserting a buffer actually worsens the overall "noise performance" of your rig; every buffer will add a little noise of it's own and also pass through more of HF content (not necessarily RFI) with whatever crud there is to start with ... and will "gain" this too mercilessly. But yeah, this could go on and on for pages....

[R.G.]

I'm going to disagree with that ... a little. High-gain circuits are very picky and there are certain counterintuitive scenarios when inserting a buffer actually worsens the overall "noise performance" of your rig; every buffer will add a little noise of it's own and also pass through more of HF content (not necessarily RFI) with whatever crud there is to start with ... and will "gain" this too mercilessly. But yeah, this could go on and on for pages....

Actually, I agree with your disagree-a-little; it's one of the things that are involved in those many pages. It's what I alluded to in that cryptic note about playing the noise game and gain structures. Adding ANYTHING in front of the actual gain stages adds the inherent noise of that thing to the mix and its noise is then amplified by the following stages.

But as a practical matter, at guitar signal levels, there are remarkably few places where a (well-designed) buffer can't be used in front of a circuit. It does make the design of the buffer and gain circuit more tricky to do well, and that gets more tricky as the following gain goes up. And as Craig Anderton noted, distortion circuits by themselves make noise more prominent by clipping off the signal "compressing" it, and amplifying noise without clipping.

You can still get yourself a lot of noise if you aren't careful, but modern low-noise opamps add remarkably little noise to a ~~100mV guitar signal.

- if you're careful. 

[Agung Kurniawan]

Using 1 regulator to supply 4 or more pedal would be awful for distortion lover (like me ) adding a buffer infront is a big problem that causing noise get amified by the distortion pedal. This once were happen to me.
But now I have built my own isolated ps to feed my pedal. And my dist pedal is quite. The noise were very low. But the problem now is I lost the treble from my pickup and Im going to find some quite buffer to place inside my guitar.

[antonis]

The noise were very low. But the problem now is I lost the treble from my pickup

You may name it as "The price of quietness"...

[Agung Kurniawan]

You may name it as "The price of quietness"...

Hahahah, my pickup were sounds bassier