[sdiy] Converting rack mount to DC input?

Sat Jul 4 17:38:26 CEST 2026

oh, i'm not concerned with like national rules or whatever, just
what's good for audio :)

On Sat, Jul 4, 2026 at 4:36 PM Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> You now come down to national rules and what your set up is.
>
> In the UK, all permanently installed bare metalwork racks (e.g. effects racks or Eurorack synth racks) have to be permanently hardwire connected to mains ground, not just via an IEC.  Large studios usually have a ground distribution screw-block on most walls.  But that doesn't mean the effects units or synth modules in those racks have to be grounded through the metal rack.
>
> And of course many racks are moveable so provided they are grounded via the IEC providing L and N that should suffice.
>
> ________________________________
> - If I have a linear PSU with -15, 0, 15V
> - and the 0V is earth referenced (i.e. shorted to mains protective earth)
> - and the rails (-15 and +15V) have kelvin leads
>
> THEN
> is it fine to just ground the devices via the 0V
> OR
> should I also earth those devices directly to mains PE via an IEC
> cable that only has the PE lead and no L/N lead?
>
> >
> >
> >
> > ________________________________
> > From: cheater cheater <cheater00social at gmail.com>
> > Sent: 04 July 2026 12:56
> > 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?
> >
> > Would I separately earth the chassis of each rack device to mains PE,
> > or would I just rely on the power supply 0V as grounding?
> >
> > Thanks...
> >
> > On Sat, Jul 4, 2026 at 1:41 PM Mike Bryant <mbryant at futurehorizons.com> wrote:
> > >
> > > Sorry yes you're correct, the CPS150 is a much simpler PSU than the others.  But I'm sure it will still be more than good enough for what you are doing.
> > >
> > > As for crosstalk between devices, that usually happens through the ground lead, not the +/- leads.  So make sure everything is earthed as much as possible.
> > >
> > > ________________________________
> > > From: cheater cheater <cheater00social at gmail.com>
> > > Sent: 04 July 2026 12:23
> > > 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?
> > >
> > > Heh, ok!
> > >
> > > A few more questions if you feel like it:
> > > 1. Is the CPS 150 still as low noise / rejection as the larger ones? I
> > > think I have one of those in storage somewhere actually, now that I
> > > think about it!
> > > 2. The 150 doesn't seem to have sensing pins in its output cable - do
> > > you know what the smallest one is that does?
> > > 3. Do you think the separate circuits of the rack devices might couple
> > > to each other via the power rails, producing crosstalk between them?
> > >
> > > Thanks...
> > >
> > > On Sat, Jul 4, 2026 at 12:59 PM Mike Bryant <mbryant at futurehorizons.com> wrote:
> > > >
> > > > They usually have an adjuster so you can set them back to 15V.
> > > >
> > > > No idea on second-tier brands 🙂
> > > >
> > > > Yes 950 is back-breaking - needs to be on wheels.  Not what you need.
> > > >
> > > > ________________________________
> > > > From: cheater cheater <cheater00social at gmail.com>
> > > > Sent: 04 July 2026 11:03
> > > > 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?
> > > >
> > > > That's cool & interesting!
> > > >
> > > > Two questions
> > > >
> > > > 1. The rack units (mostly dbx / behringer stuff since those go real
> > > > cheap nowadays for a lot of function) use 15V rails. The CPS 950 you
> > > > linked to provides 17V rails. What would I do?
> > > >
> > > > 2. Could you suggest power supplies for other mixer brands if you have
> > > > any suggestions please? Soundcraft are just a little difficult to find
> > > > here.
> > > >
> > > > Jeez that CPS-950 is a hog :)
> > > >
> > > > Oh, it reminds me I might probably need the 48V too. Good call...
> > > >
> > > > On Sat, Jul 4, 2026 at 11:48 AM Mike Bryant <mbryant at futurehorizons.com> wrote:
> > > > >
> > > > > 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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