[sdiy] Converting rack mount to DC input?

[Mike Bryant]

Yes this is a well known problem, and older top-end professional mixers with linear power supplies always put the power supply in a remote box.

Here is a typical one :  https://www.ebay.co.uk/itm/257443162756

As well as thick wires for the supplies and ground, they also had return wires so that the PSU compensated for any voltage loss in the cable, which was often tens of metres long.  I've even seen them dumped in the studio's reception to keep the receptionist warm 🙂

I think the CPS-150 was the smallest we did, but there will be equivalent small external PSUs from Midas and so on.
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From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of cheater cheater via Synth-diy <synth-diy at synth-diy.org>
Sent: 04 July 2026 10:25
To: synth-diy <synth-diy at synth-diy.org>
Subject: [sdiy] Converting rack mount to DC input?

Hi all,
Beside my head I have my mic processing rack with a bunch of preamps,
voice strips, EQs, etc. I'm in a very quiet room, and the transformer
buzz is audible, which is undesirable for my kind of work. I've been
wondering if anyone ever tried converting their analog racks to DC
input, and how that went. All the racks I'm talking about are
internally running at +15,0,-15V rails, so I could just have a single
linear (or even high quality SMPS) power supply, distribute it via XT
or XLR style connectors, and have simple filter boards inside each
unit that filter the incoming DC, with switch to disconnect the mains
PSU and connect the DC board. I was wondering if this is a good idea
in general and in particular how this relates to issues like ground
loops and EMI pickup. My run from the DC power supply to the rack
would be about 2-3 meters long, but it would be running parallel to
some digital cabling. I would also be interested in suggestions on
connectors to use, especially if I want to make daisy chain cables
that go from device to device.

I would appreciate suggestions / experiences on the topic.

Thanks!
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