Mobius Trip Looper Problemos (schem errors?)

[El Heisenberg]

I finally got the package from small bear. Went right ahead breadboarding it. I breadboard everything first and it's looking like a bad habit with bigger circuits.


http://www.generalguitargadgets.com/pdf/ggg_mobius_trip_analog.pdf

http://www.generalguitargadgets.com/pdf/ggg_mobius_trip_digital.pdf


Only difference from the schem is that I used TL074 quad pamp. I used the wiring diagram that's out there for easy stomping.

First, before I even checked if it looped, I couldn't get the red LED to turn on. After scouring over the breadboard I took a look at the PCB layout here:

http://www.generalguitargadgets.com/pdf/ggg_mobius_trip_pcb_lo.pdf


I noticed that on the PCB, pins 8 and 9 of the 4001 are not grounded, like they are in the schematic. They are connected to the pins 12 and 13 junction. I corrected this on the breadboard and there wasn't any difference. Then i decided to see what happened if I fed the LED from pin 10 instead of 11 and it works perfectly now.


But the looper...


The dry signal sounds fine. But the playback is terrible. It sounds sputtery and splatty and distorted ina  really bad way. It's thin and totally now what it should be. I know this isn't what it' sposed to sound like.

I tried putting the LED setup back to where they were but no difference either way. It's a problem with the op amp or the ISD1020 chip.

Does it sound like I fried my chip on accident? I've scoured over the breadboard and it all looks like. Could it be noise? Could the digital noise and stuff really mess up the loops sound that bad? I did put all the coupling caps very close to the ICs. Tried to do as much as I could to reduce noise on a breadboard.


It works, it's just crappy. Real crappy.

[El Heisenberg]

Argh help. Feel like crap. Been waiting for the package for a week and a half cos small bear forgot me! And when it finally gets here I get weird stuff on the breadboard. i actually dreamt about this project one night I was so excited. I kept waking up in sweats. I wanna get this done!

[El Heisenberg]

Hah! I got it workin. I can't beleive it. I told myself I'd never post here about a problem that would turn out to be crappy breadboard. The TL074s pins weren't touching the freakin rails. I had to press down on it with a screwdriver and the loop came to life all bright and clear. The thing works perfectly. No noise. It wouldn't stay that way, so I popped in an NTE version of the quad op amp in and it works.


Now to add a tone control and figure out if I can do vibrato.

But isn't my 4001 red LED problem weird? The schem and the PCB are different, and I couldn't get mine to work without doing something different than both.

[deadastronaut]

i looked at the datasheet and it says 6-8 khz..sample rate..

thats gotta sound rough.. does it?.. rob.

[El Heisenberg]

Nope sounds fantastic. You can actually tell your guitars signal from the sample.