Hello! My name is Facundo, I'm from Argentina, and it's a bit challenging to get FET transistors here. It's even harder to find them at a good price and in original condition. That's why I'm very interested in this topology using op-amps, which are affordable and available almost anywhere. Today, I designed a PCB for the SLO MKIII circuit, but I omitted the input and output buffers, and I also didn't include the tonestack.
When testing the circuit, I noticed that the sound was intermittent, as if a noise gate were active. I assumed this could be due to the lack of an input buffer. I built a buffer using a BC547 transistor I had on hand, based on the schematic by Jack Orman at http://www.muzique.com/lab/buffers.htm
(the first one with a bipolar transistor). When I placed it at the input of the SLO MKIII, it started to sound as it should, but with a quite annoying squeal. I haven't tried adding a buffer at the output to see what happens.
So, my question is: Do you think the squeal I'm hearing might be because I'm using an incorrect buffer for the required application, or could it be due to the lack of a buffer at the output?
Thank you for reading my message, and I hope it's understood clearly, as I'm using ChatGPT to translate it.
EDIT: I had a quite busy afternoon. I built a dual buffer (http://effectslayouts.blogspot.com/2016 ... uffer.html
), but I didn't get any sound directly. I had a problem in the buffer circuit as well, which I managed to solve.
In the end, after spending the whole afternoon racking my brain, I could find the issue. I missed connecting two components when I designed my PCB in Eagle for the Baja SLO MKIII.
I made a bridge on the circuit board, and it started sounding wonderful.
In these days, I'm going to add a tonestack to it and test it as a preamp.