fx loop: promising results

https://youtu.be/gHR9m0GR7P0

So I applied both of the "technological" solutions discussed in the previous entry: i.e., snubber cap on the EL84, and 13 kHz LPF after the master volume pot.  The latter seems to have fixed the oscillation issue.

Next work is to fit the replacement v-mid eq circuit board into the box, and then test all the amp features and functions before buttoning it up.  E.g., I have never fully tested the fx loop with an actual effects unit, I have merely adjusted its gain and fixed the oscillation issue it was having.  Also, most of the non-relay switches (the four on the upper back panel) have never been tested, or only minimally (voice, scoop, bright, and coldness).  I just need to comprehensively run the amp through all its modes and extremes of operation.  Because, cramming it all back into the chassis box is such a nightmare, that I'll hope to never need to repeat it again!  After shipping this prototype, I will implement the final circuit on a proper PCB, with a mind towards serviceability.  If the prototype ever comes back to the shop for repairs, I'll likely just swap out the janky hand-wired guts for one of the manufactured PCBs.  So it is indeed possible that it will never need to be taken apart (carefully) again.


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