Learning about buffers (DIY, not looking for pedal recommendations)

Yorkie

I know nothing about buffers from a design point of view. I am having the time of my life designing/cloning/experimenting with effects circuits for my own consumption, but buffers are the one circuit I've avoided so far. I think I would like to breadboard one and see what I can learn. 

What's a good place to start? Where can I read about buffer design from a guitar stompbox perspective? 

Many thanks,
Jon

robinbowes

https://www.planetanalog.com/buffer-amplifier-design/

https://youtu.be/1wMqNRvMUsY

Sporky

If you want to get fancy, an op-amp follower, optionally with a charge-pump voltage doubler, is another approach. 

Yorkie

robinbowes said:

https://www.planetanalog.com/buffer-amplifier-design/

https://youtu.be/1wMqNRvMUsY

Thanks!

So it turns out I already knew how to build a buffer – every boost, drive or fuzz pedal I've made so far is designed around that idea. 

robinbowes

Many circuits have a buffer at the input, yes.

Yorkie

robinbowes said:

Many circuits have a buffer at the input, yes.

No, I mean how a booster circuit can just be a buffer with a gain control and little else. For example, the EQ-ed "Treble" Booster I built here: https://www.thefretboard.co.uk/discussion/246132/treble-booster-vs-boost-with-3-knob-eq#latest

robinbowes

Ah yes, that's entirely true.

There are some great resources on the AMZ site: https://www.muzique.com/

In particular, the MOSFET boost is well worth building: http://www.muzique.com/schem/mosfet.htm

R.

Yorkie

Well, that's great. I didn't know about that resource. So cool. Thank you so much.

Danny1969

One thing I would say is don't limit yourself to thinking about guitar pedals and circuits, even if that is what you are interested in. Learn some basic electronics and then see how that applies to guitar pedals. The reason I say this is because a lot of guitar pedals schematics are kind of done in their own way and a bit misleading in their terms. They also tend to rehash the same ideas again and again. 

Some books I recommend 

Small signal design - Douglas Self 

Opamp cook book - various versions but once you see how versatile opamps are there's enough cookbooks to keep you in designs for years

robinbowes

Douglas Self's site: http://douglas-self.com/ampins/ampins.htm

Yorkie

Danny1969 said:
One thing I would say is don't limit yourself to thinking about guitar pedals and circuits, even if that is what you are interested in. Learn some basic electronics and then see how that applies to guitar pedals. The reason I say this is because a lot of guitar pedals schematics are kind of done in their own way and a bit misleading in their terms. They also tend to rehash the same ideas again and again. 

That's the approach I'm taking, yes. Although so far it has led me to sort-of reinvent some of the simpler circuits out there, I believe at some point it'll pay off.

Small signal design - Douglas Self 

On its way. Will study it during the holidays. 

Yorkie

Sporky said:

If you want to get fancy, an op-amp follower, optionally with a charge-pump voltage doubler, is another approach. 

Interesting. Can you point me to an example please? I've got a few op amps here.

Yorkie

On holiday, reading some Self. 

“Do not forget what the Prime Directive of audio design is — Thou Shalt Not Kill”. 

Watson, please bring me that wasted hound of yours… 

Sporky

Yorkie said:

Sporky said:

If you want to get fancy, an op-amp follower, optionally with a charge-pump voltage doubler, is another approach. 

Interesting. Can you point me to an example please? I've got a few op amps here.

I use(d) these for the voltage doubling:

https://www.rapidonline.com/intersil-icl7660scpaz-cmos-voltage-convertor-82-0788

The spec sheet there includes application schematics, but basically you chuck 9v in and get either -9v out or 18v (ish) so you get much more headroom in the circuit you're powering.

Opamp followers are a really basic configuration. 

https://www.allaboutcircuits.com/video-tutorials/op-amp-applications-voltage-follower/