Ashly SC-50 Black Face Schematics?

Does anyone have a readable scan of the Ashly SC-50 schematics (black face model). I picked one up recently and plan on doing a complete rebuild to clean it up, because they are a little noisy.

Ashly was kind enough to e-mail me a schematic, I'm not sure what revision it is.
http://img685.imageshack.us/img685/7222/sc50schemolder.jpg

According to Ashly, this is the only schematic in their archives but it should be pretty close no matter which revision you have.

Looking for a schematic for an early SC-50 compressor - does anyone have it?

Nick Froome

Here you go!


btw... I love that comp! I have SC-55 (same but dual channel) - the best thing on electric guitars!

Had a very helpful - and very prompt - reply from Ashly to my email. The schematic above is for the early version of the SC-50 which uses matched pairs of transistors in a metal can. This is the type I have. The later version uses a dbx chip

According to Jim at Ashly: "If you do have the original version SC-50 with the matched dual can transistor VCA, it is important that no substitutions be made concerning the IC chips. The circuit was designed around a special mode of operation only available in the 301 IC"

Thanks for the help, shot & Jim

Nick Froome

Is there any chance to get the schematics for the SC-50 again?

Here's an Ashley SC50 schematic I have.

Thank you!

You may notice that the op amps used in the stock SC50 are not the greatest by today's standards. A few months ago I did a comprehensive mod on a pair of SC50s that addressed this. The 4558 used to make the balanced input can be replaced by a THAT 1200 balanced input chip. These offer a great solution to the difficulty of achieving the promise that balanced lines try to achieve. The quad 4136s are basically (4) 741s in a single package and suffer from low slew rate, higher distortion, poor signal to noise, low current delivery and offset current and voltage. I stacked a couple of 8-pin sockets onto each 14-pin socket with some crazy cross wiring to accomodate a pair of LM4562 duals to replace them. The SC50s balanced output is a nutty stack of 4558 sections to try to drive balanced lines. I might have used one of the TI-Burr-Brown DRV 134 balanced output chips. Since the LM4562s have a much higher bandwidth than this circuit needs, I trimmed the negative feedback resistors to cut off at 159kHz to they won't amplify every radio station in town. I also added several 0.1 uF supply bypass caps at several spots in the circuit. It came out sounding very good. I'll look through my files for details and photos of how I stacked those chips, etc, if you're interested.