[sdiy] Converting rack mount to DC input?

[Mike Bryant]

Yes that would be fine - it's effectively what happens in a large mixer.  It's a long way from one end to the other of a 48 channel analogue console 🙂

They are also designed so you can put two in parallel so providing fail-safe operation for live use.  Being out in the middle of a concert hall mixing can be a precarious place to be when the sound dies, but you probably don't need that 🙂

You'll also find the power line noise on these units is probably better than your present supplies.
________________________________
From: cheater cheater <cheater00social at gmail.com>
Sent: 04 July 2026 10:44
To: Mike Bryant <mbryant at futurehorizons.com>
Cc: synth-diy <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Converting rack mount to DC input?

Thanks Mike. Do you think sharing one large PSU across many rack items
will be fine? I mean the whole stack currently takes less than 100W
mains. My guess would be to short the kelvin sensing pins to the rails
where I get close to the first rack item and then just distribute the
three rails (+V, -V, 0) without any sense wires.

On Sat, Jul 4, 2026 at 11:36 AM Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> 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.
> ________________________________
> 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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