Studer 169 EQ Clone Pt. 1

Quite a few years ago Audiox posted up a nice 500 series clone of the Studer 169 EQ section. I haven’t used this mixer before but have always been infatuated with the Studer/Revox designs and aesthetic. It is a fairly simple circuit and decided to design my own PCB for this project. To be clear from the get go, full credit to Audiox for this project – I worked 100% off his schematic. I’ll be building 8 of these into a 3U rack enclosure.

GroupDIY Link to the Audiox original

PCB Grinder link to PCB purchase page

There aren’t many differences between my version and the Audiox, but my one will have switchable frequencies on both the high and low band. It also isn’t going to be a standard 500 series module.

The PCBs came in yesterday so I got soldering right away, but still need a few more parts before I can test the boards. Still, I’m pretty happy with how they are looking and thought I would post something about it.

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I don’t have any spare 2520 style opamps lying around so decided to quickly whip a NE5534 adaptor up:

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As an aside, A few years ago when working on a uni campus I came across 6 Revox A77 machines, all of different vintages, in a skip when a Drama faculty was being relocated. I sold 5 of them onwards but kept one for myself. I recently finished repairing it and am pleased to say that my lovely old 1974 Revox A77 MK.III tape machine is in fine working order once again! This received a full recap and new trimpots curtesy of the StellaVOX kits. This one was blowing the 2A fuse on the 27V rail, a fault which was traced down to a bung 1N4148 diode on the braking system solenoid. This solenoid (72 ohms @ 27V) draws roughly 0.35A so it isn’t any surprise the 1N4148 kicked the bucket in the end. I replaced it with a 1N4003. Annoyingly this is missing the tape counter and had a few signs of being opened and repaired before I got it.

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And Done!

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