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Well, here it is:


GAR2520 on channels, 1731's in summing and Red Dot's in booster. Elma 24 pos rotary switch, Bourns and BI  center detent potmeters. Aluminium milled knobs and plastic labels on I/O (from Redco, where I got the custom 48 channel loom (12 DSUB's on one cable!) to hook the mixer up to my patchbays). All direct outputs trimmed to unity gain, notice the trimmers (on all 24 channels  ::)) This thing has been on my bench (read: kitchen table) way too long. I'm happy with the result, but man was it alot of work. Now going to put it to good use!
Hi folks,

decided to ditch the DR psu, as it kept getting too hot even with the maximum size heatsinks allowed in the enclosure and 333/338 regulator ic subs.
Changed it to a JLM smps (the one for 500-racks, 2A @ +/-16V) with the fet swicher kit. Super easy replacement that performs rock solid, cool and quiet. Gained at least 10dB headroom on most channels!

I gotta say though, that my build is pretty sensitive to mechanic manipulation, as in my wiring / crimp technique / choice of cheap "molex" contacts makes it almost inevitable to slightly nudge a cable or two while moving or re-racking the mixer. And since the enclosure and stacked boards approach is such a pita to work with I am sick of de-assembling and re-assembling it just for it to be nudged again in the future.

Don't really understand why these pcb's don't just come with db25 footprints at the back instead of the 3-pin 2.54mm style contacts that don't allow for chunky screw terminals. Guess I could fit the tiny Phoenix terminals and use ferrules, but it isn't very sturdy either, at least when the terminals are spread all over the board etc.

Imagine this project with db25 at the back, pre/post fader switch and room for trimmers on the direct outs (and maybe a DOA alternate footprint for the direct outputs if one wants it totally classic? Could have extra connector footprints by the output db25's to connect to output transformers..) and footprints/pcb mounted pots. Would be so much quicker to build, and eliminate most of the mistakes that happens due to inferior wiring skills and sturdy board connections, in a case that fits snugly around the pcbs and a design that allows one to work from the bottom like the NRG cases etc.

It sounds really great though, and is finally a workhorse with the new power solution!
Good luck finding it. Got a half-way draft (of the input section only) from the DIY tech way back, that I've unfortunately misplaced.

You can have a look at the JLM Dingo schematic as an example for the input section (just a normal differential op-amp receiver (r3-r6/c1-c4 on JLM schem, with slightly different cap values (Cx-1 to Cx-4 and Rx-1 to Rx-4 on DR2402 pcb) which after cx-5 (dr2402) is split to the direct output (see attached pic from the 1646 datasheet) section through a resistor (R-x_9 I think, on the DR pcb), and a pan-pot section (pan potmeter/molex connector and associated resistors rx-5 and rx-6.

rx-7 and rx-8 would be your bus resistors, getting its signal from the pan resistors, and outputs them to the two mix busses which in turn goes to your ACA inputs (see Capi schem).

No idea about the LED-section schematic, but I'd guess a generic comparator style opamp amp setup involving the resistors and diodes below the 074.


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    1646 section.png
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  • dr2402 ch.png
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