Clipping Stage: Op Amp vs Transistor

[Premium.Dirtbag]

Morning,

I realize this is a bit more baseline that the usual fair but I'm quite new to everything and would rather ask ya'll than go off some 10 year old Gear Page misunderstanding.

I'm onto refining a breadboard distortion I made and came across a schematic that used the same circuit as our initial jumping off point. However, they utilized three NPN transistors to create the Op Amp circuit. As a result, the gain structure is clearly set up differently. I'm curious if a transistor set up yields a sonic difference worth experimenting with and if so, any advice for subbing some in for an op amp in a breadboard that's already wired for the latter?

Thanks!

[Nitefly182]

Just wire up the new circuit on another part of the breadboard and use jumpers to move the signal between the two for comparison.

Can you share a schem of the transistor version? If its some sort of very rudimentary opamp you would potentially run into issues with inconsistency between builds if the devices weren't matched.

[antonis]

No schematic..?? Nothing..??

[Premium.Dirtbag]

Ha, that would help. I was comparing the Catalinbread Katzenkonig vs a mutant Rat I've made. Basically I've just added clipping options and I've added an input buffer.

https://www.docdroid.net/joL2PWr/catalinbread-katzenkonig-pdf

https://www.electrosmash.com/images/tech/pro-co-rat/pro-co-rat-schematic-parts.jpg

I've got some BC108s and will sit down with them when I have time but I was just curious if there is some clear sound advantages/disadvantages versus transistors and op amps in this set up/if its worth the time.

[aron]

I remember making this and loving it:
https://www.diystompboxes.com/analogalchemy/sch/diodeopamp.html

[antonis]

they utilized three NPN transistors to create the Op Amp circuit.

Uitilization of 3 BJTs for creating op-amp circuit brings me in mind something like a differential pair followed by a voltage gain stage..
Definately not something like 3 cascaded CE amps with shunt-series feedback between the last 2 of them..

That's the reason for asking for particular schematics..

[iainpunk]

they utilized three NPN transistors to create the Op Amp circuit.

the katzen köning doesn't have an opamp, tis basically the gain structure of a fuzzface/tonebender.

they will sound very different; the op amp has a way more linear response, while the katzen köning had less linearity in it...
it is basically a matter of taste.

cheers,
Iain

[Frank_NH]

I've experimented with simple discrete op amps (two jfets + two BJTs) and created a tube screamer design that worked well.  You can get the schematic and vero layout at this link:

http://guitar-fx-layouts.42897.x6.nabble.com/D-Tube-A-Discrete-Op-Amp-Overdrive-tp41274.html

The discrete op amp seems to make a small sonic difference, providing a little smoother distortion to my ear.   What's fun about the discrete op amp approach is that you can experiment with a wide range of designs and tweak them to taste.  Also, I think discrete op amps are best used for the gain/overdrive stages versus active tone controls or buffers, where simpler discrete transistor designs will do.

By the way, this approach is not novel as Boss has used it the Blues Driver, OD-2 and OD-3.