No buffer stages in DIY Pedals?

[CaptainKY]

Is there any reason the DIY pedals (that I've seen) don't have buffer stages to guarantee input/output impedance levels and isolate the pedal from the others it is connected to? Something like an LM741 buffer was what we used a lot in my electronics classes.

These effects sound really cool so far from the ones I have built but are a good example of what I am talking about
http://folkurban.com/Site/GuitarEffects-681.html

[gnasher1993]

Some circuit designs use jfet transistors as buffers.

[dune2k]

You don't NEED to have them & in some projects gain stages or so act as a boost and buffer. It's also quite simple to just build one or two good (!) buffers and put them on front of/after your other pedals.

Some old pedals which a couple of DIY designs are based upon don't like buffers (eg. simple transistor fuzzes).

[Silent Fly]

As it has been said, some pedals can work well without buffers. Others need them.

Sometimes some schematics like these are just a starting point. Adding a buffer can improve the performance but it doens't add anything to core idea.

Buffers can also be designed unsing jFET and BJT. You can find example in a lot of Boss pedals schematics.

[bongomania]

Plus you have to distinguish between a buffer in the bypass mechanism versus a buffer in the effect signal path. Those two get conflated way too often.

Most effects, DIY or not, do have a buffer in the effect signal path. It's often a poorly-implemented buffer (in terms of line driving), but it's there. There are two main reasons I can think of why many of them are not good buffers:
1) The gain stage needed for the effect circuit often has to be placed before other components/stages that incidentally raise the output impedance.
2) It's more expensive and complicated to redesign existing circuits for lower output impedance, and the vast majority of DIY and boutique pedals are just repackaging of variations on pre-existing circuit designs.

So since the vast majority do include a buffer, but not a good one for line driving, that raises some questions:
--What kinds of effect circuits can be made that include no buffer whatsoever?
--Which pedals on the market happen to be very effective buffers when engaged?
--Which pedals happen to be very effective buffers when bypassed?

[Silent Fly]

Originally Posted by bongomania

Plus you have to distinguish between a buffer in the bypass mechanism versus a buffer in the effect signal path. Those two get conflated way too often.
(...)

Excellent point. I agree.

The first should be called something like "bypass with electronic switching" or “active bypass switching”.

Originally Posted by bongomania

--What kinds of effect circuits can be made that include no buffer whatsoever?

In theory any effect that has high input impedance and low out impedance doesn't need any buffering.

In practice not many circuits allow that. When the last stage is an op-amp, a buffer is not always needed but high impedance inputs are less common.

Originally Posted by bongomania

--Which pedals on the market happen to be very effective buffers when engaged?

For obvious reasons, I can’t comment on this but designing a good buffer (i.e. low noise, high headroom, good in/out impedance...) is not that difficult. The point is, as always, not what but how and why.

Originally Posted by bongomania

--Which pedals happen to be very effective buffers when bypassed?

This is a tricky one.

The best buffer in the world will, inevitably, add something to the signal. If it is well designed and implemented it is likely that what it adds is below what we can hear.

However, if every pedal adds something as we use 10 pedals the cumulative effect of all the buffers in the chain can be audible. This is why true-bypass has its merits.

IMO, in an ideal world, a pedal board with more than 3-4 pedals should have an input buffer (the micro-thumpinator springs to mind), an output buffer and the pedals working in true-bypass.

The buffer should also have an electrostatic protection to discharge any charge that may be present on the musician side. This protects the pedals on the pedalboard.