Laurens Primusz

Next in my modest assembly line: a 500 series Studer 169 EQ, created by GroupDIY member audiox. Got the idea from browsing the GroupDIY forum and decided to do the  full-on mojo build with Discrete Opamps and Transformer balanced input.

This is what the finished pair looks like:

Since the frontpanel had an extra hole provisioned for an LED I had to swap the DPDT switch on the build plans with a 3DPT switch. The LED takes voltage from the nearest 16+ rail point i could “hook” into and returns to an unused solder pad nearby that returns to ground.

Although the potmeters provide a means to attach a frontpanel to the PCB I decided to go for something a little more sturdy and mounted the PCB on L-brackets.

First mounting of the front panel. The switch I used first didn’t really fit the frontpanel’s hole, so a little rework needed to be done.

My initial, unmodified build:

List of materials/sources:

• PCB’s from PCBGrinder
• Components from Mouser, there’s a premade Bill of Materials somewhere in the GroupDIY thread
• Generic premade frontpanel from Frontpanels.de
• L-brackets from silent:arts (can also be ordered from ClassicAPI in the US)
• Dual gang Omeg potmeters from Audio Maintenance (though Conrad carries these as well apparently), as specified in the GroupDIY thread
• gar2520 opamp from Classic API for the mid band
• opamp from Vintage Audio Projects for the hi/lo shelves (no site available yet..)
• replaced the DPDT switch on the PCB with a 3PDT toggle switch from musikding.de, where i got some mounting materials from as well

I love the sound of the hi/lo shelf on these!