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Electronic Repair & Modifications

Blogs related to recording equipment repairs and modifications

Symphonic (Pine Electronics) M13 Amp Re-Build/Partial Re-Design

Member for

14 years 5 months

Latest Rabbit Hole project....Started with adding a line isolation transformer and morphed into a complete circuit rebuild... The original circuit was pretty much a widow maker design, with direct line voltage feed the amp.

1178 Channel A "Railing"

Member for

14 years 5 months

One of favorite units, the 1178 is a very useful tool. This one has an issue when the needle intermittently pins hard right. It took a while to replicate the issue on the bench. It might be a cap, cold solder joint, opamp?


I don't know yet, I am going to start to trace the problem from the output back to the input.

Stereo Width Experiments

Member for

14 years 5 months

 I am getting interested in building a hardware stereo image widener circuit.  I have seen a few ideas floating around based on the Middle(M) +Side(S) technique.  The basic premise can be summarized into the following equations:

Encoding M and S

Middle  = L+R

Side  = L-R

Middle Circuit

Translating that into basic op-amp circuits, the Middle signal could be created with a summing amplifier.