Redbox

[Kipper4]

Has anyone built this?
Can you foresee any potential problems with the circuit.
Suggest and improvements.
I'm guessing they're using 1/4watt resistors.
Any help will be great fully received.


http://analogguru.an.ohost.de/193/schematics/H&K_RedBox-MkII.gif
Sorry if anyone's offended that I posted the link

[aron]

I have one. It's ok - not great.

[corythosaurus]

I built one into a distortion pedal once to try it. It didn't blow me away, but it was pretty nice, and it's certainly a fairly simple circuit to put together.

The biggest change I made to this was using a different circuit to drive the XLR out and to create the negative signal on the XLR out. The circuit here works fine, I just have one that I like and I'm used to.

You can get some different tone if you change C8/9/10/11. I ended up making C9 and C11 a little smaller (150p or 180p I think) and it opened things up nicely around 3khz or so.

[Kipper4]

Interesting
Thanks Aron for the critique.

I'd be interested to see how you changed the circuitry please Cory.
Thanks

[corythosaurus]

I didn't really do much, tone-wise. The biggest things were C9 and C11, which I mentioned - that made it a bit brighter and more open without becoming fizzy/brittle. I think I experimented with changing C8 and C10 to 1.2nF. I think I changed them back to 1nF, but that mod is worth a try.

The only other changes I did weren't tonal, just utility type stuff. I put a really good buffer before C3, since I was coming off of a guitar-level signal. Then, after pin14 of IC1, I sent the signal to two opamps, one inverting, the other noninverting, to drive the XLR. Not super necessary, but I had the space and ICs handy for it.

If I were you, I would try building or breadboarding one, and swapping out a few different values for C9/C11, to see what you like. There are some decent tones in there!

[Kipper4]

I'm thinking of subbing out the op amp for a TL074 . Can anyone see a problem with this?
Thanks for the advice Cory.
I might try and breadboard it over Christmas. Knowing me I'll just go ahead and make a diylc perfboard layout and make a pcb as per.
Thanks for all the help