Oscilator problem

[bzblues]

Hello everyone!




I have a little project on the workbench that I'm having trouble with.




I must say that I'm a beginner, so be patient if I'm not using the right terms.




The project consist of six simple oscilatores (using the SS9018 transistor) conected to a simple "ruby amp" the one with the LM386 chip. Everything works with 9V.

I also added a guitar jack so I can play guitar while the oscilators are playing as well.




So, I group all the oscilator outputs into one, conected them to a 100k potentiometer so I can control the volume of the oscillators independently from the guitar signal, and conected the oscilator out signal along with the guitar signal to the input of the Ruby amp.




Now, obviously I had some issues because the guitar signal affected the oscillator signals and viceversa. So I did some reseach and I found out that I must add two "buffers" using the TL072 op-amp only. I followed the instructions on how to connect everything but all I'm getting is a squeaky noise, so obviosly something is not working out propperly. I checked and re-checked every connection, and everything seems ok, but still doesn't work out.




I'm guessing that it has something to do with the 9V surelly. Anothe option was a "voltage divider" (two 10k resistors, one to 9V and the other to GND and from both resistors to feed the buffers, but that also didn't work out.




Again, sorry if I'm not describing it the right way, I'm learning.




Thank you!

[g1]

Were you getting proper oscillator sounds before you added the buffering? Can you post or link the schematic/info for the buffer?

[Jazz P Bass]

It sounds like it all worked until the guitar signal was added.
Added where?
I would suggest that the OP reads this article as it covers it all.
Naively mixing two (or perhaps more) audio signals - Electrical Engineering Stack Exchange

[Mick Bailey]

If the oscillators combine OK into one signal and don't interact with each other, they can be fed to one end of a pot, the guitar into the other end and the output taken off the wiper. A 100k or 220k linear pot should work fine. The pot behaves like a mixer - at extremes of rotation you get pretty much oscillator only, the other end guitar only, with a variable mix in between. I use this method in my guitar synth build and it works fine.