As I indicated in my previous post, just to assist more: This sounds suspiciously like the noise I had on my 5210 when the output of the JFET (TR1, I think) had a dc bias that must have drifted over time and caused reverse bias voltage on the coupling capacitor that comes directly after it...
I had popping and static sounds years ago on a 5210. See my other response, but to summarize I found that one of the tantalum coupling capacitors was reverse biased slightly (cannot recall which). Replacing it with a bipolar electrolytic cap fixed it permanently. The circuit was assembled...
I have a better copy of the schematic. No diode clipping is used.
I do not usually try mods, but I did try a different Op Amp in my 5210 (tried a NE5532, hoping it would give better cleans). Result: It sounded terrible, and had the muddiest overdrive tone I have ever heard. I immediately...
I had a friend who said that his 5210 had been in repair shops several times with a similar crackle/pop that could be heard intermittently. No one could find what was causing it.
He gave it to me and I had a look at it, made some measurements, and discovered that there was a tantalum capacitor...