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:
![studer duo finished](http://www.laurensprimusz.be/wordpress/wp-content/uploads/2015/08/IMG_20160831_193447-568x1024.jpg)
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.
![IMG_20150817_184718](http://www.laurensprimusz.be/wordpress/wp-content/uploads/2015/08/IMG_20150817_184718-1024x768.jpg)
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.
![IMG_20150807_214415](http://www.laurensprimusz.be/wordpress/wp-content/uploads/2015/08/IMG_20150807_214415-768x1024.jpg)
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.
![Mounted the frontpanel…jup, something's not quite right..](http://www.laurensprimusz.be/wordpress/wp-content/uploads/2015/08/IMG_20150630_221414-e1438633889414-768x1024.jpg)
My initial, unmodified build:
![Studer 169 EQ PCB fully populated](http://www.laurensprimusz.be/wordpress/wp-content/uploads/2015/08/IMG_20150615_085011-1024x768.jpg)
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!