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The mysterious ancient Korg powered stage monitors

Posted: Fri May 19, 2023 1:46 am
by mike_h
This is an expansion on a previous post in the "testing this forum" category,
I submit this here because it is synth related and there appears to be nowhere else to post it.
That being stated...I am referring to the mysterious SM-75 and the little sibling PM-30. Both are vintage 1985.

http://www.korgforums.com/support/broch ... ochure.pdf

I serendipitously have come across one of each.
I like them both a lot...I use the SM-75 on gigs regularly.
It is very sturdy and dependable and yields a solid sound through a simple design with quality components.

Searching for another has brought crickets, although I have recently won a bid on a SM-75 on a Japanese site. Waiting for delivery details to transpire.
Japanese AC is 100V. I was looking for a schematic to see if I could tap the transformer to get it to accept 120VAC, but crickets there also.
I will probably end up getting a step-down transformer.

I did talk to two techs who said they came across these back in the day. They said the amp was a design they could work on without reference documentation!

So I am reaching out to see if anyone has or has had or has seen any of these?