microsynth report + questions

[swt]

hey guys!!. Just finished my microsynthesizer clon. It works...but i'm getting really low signal, and also it distorts a bit if i have the preamp high and add triggering on it. So here are the questions: i haven't got 2n5088 and 2n5087, so i've used bc 337/338 respectively. Can this be the reason of the low gain, because if i read the circuit properly this trannies will bias the ota at the end of the chain right?. Any ideas?. Maybe changing to bc549c, and 560c?. Can anybody suggest something to me?.
I had to change the 1k resistor in that ota, the one that goes from pin 2 to 3 and put it from 3 to ground and also grounded pin 2, as i thought this was wrong. So i'll be waiting for someone kind to help me, because this circuit is funtastic!!!!!

[Bill Bergman]

If I remember, there a wiring bug some where in the input section that sucks the volume down. There also a trim pot I brought out to a panel mount pot that allow extra volume boost.

[swt]

I knew you will show up!. Do you remember if that bug was caused by a circuit error, or only by layout mistake?. I mean...just want to be sure that the circuit schem is correct. Do you remember what was that?. I'll keep you informed about my advances, as it seems we are the only ones messing with this one. Thanks a lot man!

[swt]

another one....what's that squelch pot for?.

[swt]

i'm damn heavy with this thread but...hope it's worth the effort. I was looking at the input section, and find nothing relatively wrong. Is that 68k resistor really good for guitar?. I mean...woulnd' it be better to have something like 1m to have the right impedance?. Also...is that preamp pot wired correctly?. It looks ok, but i will experiment a little more tomorrow. Thanks again!.

[Bill Bergman]

SWT,
I think it was somthing to do with the wiring between 2 of the 3 pcb's on my layout. Did you use mine or did you make your own. Perhaps, if you want to talk about it, you could give me a call. I'm an slow typer.

[Bill Bergman]

oops,
are you from Chile? A phone call may not be the best idea. I guess we better stick with e-mail or the forum

[swt]

Thanks Bill. I'm from Argentina, way way south of America, a place called patagonia. I've used your layout/pcb, but made the corrections i think it needed, according to the schem. The fact is, that right now i don't know if that schem is accurate. I think there are some errors in it. That's why i'm asking if you follow that schem and it worked. I'm not used to the use of 3094s, but it looks as the output section has something wrong. I've checked the input in mine and it works fine, even after the 700hz filter. I'm at a point where i think it's the output mixer. IS it correct to use pin1 as the output of a 3094?. I thought pin 6 is the output. If this is wrong, then the suboctave is also wrong on the schem. Well...let's keep experimenting. Hope i'm not bothering you too much. Really...really...thanks.

[Bill Bergman]

SWT,
no bother at all. I just wish I could be more help. I think I trashed all my building notes(that was stupid). Let me try and remember or even open up my unit and see if I can figure out what I did.

I think the squelch is a balance between the +/- voltage. It kind of sustains or cut the played note.

[swt]

Further advances. I was wrong. I think they are using the output ic 3094 as a standard 3080, that's the reason why they are not using pins 6 and 8, and they use pin 1 suppossed to be an input, as the main ouput. So now i'll have to double check that bias section, because it sounds as a misbiased problem. If you are so kind to open it up...can you check if you had to change something in that output section, and also how you wired that 1k resistor in ic 14?. Thank you so much!!

[Bill Bergman]

I think your right about the CA3094. I'll check for any extra jumpers I might have used. You might try not grounding the connection marked #1 on pcb 2. Seems like some where in that area is where the problem was.

I can't even remember who helped me with the bugs......F.P., Rob Strand, J. Luja.....etc