Chorus fun!

[$uperpuma]

so I got a signal flex chorus for dirt cheap a GC today.. plugged it in, its a little noisy, and seems choppy... so I opened it up it had the old 3102/3207 pair two jrc4558's and another dual opamp that looks like a replacement, KIA 358p... I haven't been able to find a schematic for it to see if this was the original part. if its a replacement part. maybe its the rason for the slight choppyness... so should I mess with fixing this or does anyone know of a project with a PCB layout for a chorus that uses these chips... the tonepad CE-2 uses the updated ships, IIRC... anyhow...opinions?

[GibsonGM]

A place to suspect noise & chop might be the opamps, the 4558's...they're not exactly high fidelity.  But then there's everything else...shielding, component placement, using shielded wiring for offboard components. 

If you want to play to learn and don't care if it dies, maybe pull out the 4558's and put in sockets to compare how a TL072 sounds?  They might need better adjustment of operating parameters, too.  Look at the wiring, maybe shielded stuff could help?  Search hi & lo for a schem, start putting in good caps in the filter sections & signal path?   You could do a lot, but start slow and logically     You might be able to make something really cool out of that thing...

[$uperpuma]

yeah so far, my #1 suspect is the lm358 as it looks to have been a resoldered replacement, just by looking at the solder side... I'm going to start there maybe socket it to try 072's or another 4558 I've got some of both...

anyone else have any ideas on what to do with the parts if I can't get this one soudning right?

[$uperpuma]

Hate to bump, but if anyone has anyfeedback on this one I'd be very appreciative...

[Gringo]

From my small clone experience, the lm358 is the dual oa that handles the lfo, and when i tried anything other than a lm358, the lfo didn't work. You can try a better dual on the audio handling positions, but i'd say leave the lfo one alone (at first ).