[sdiy] Converting rack mount to DC input?

Tue Jul 14 14:24:56 CEST 2026

oh yeah, no chance of that happening here, it's only for my own personal use.

On Tue, Jul 14, 2026 at 2:22 PM Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> GX16 was the standard for lighting control voltages to the dimming racks before DMX appeared.  Very rugged and excellent choice.  Had the occasional wire break inside the connector due to bad roadie level handling, but very rare.
>
> ________________________________
> 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: 14 July 2026 13:03
> To: David Huss <dh at atoav.com>
> Cc: synth-diy at synth-diy.org <synth-diy at synth-diy.org>
> Subject: Re: [sdiy] Converting rack mount to DC input?
>
> Hmm, GX16 is interesting, thank you! Let me see if I can find one with
> 8 pins easily - that's the minimum that I need (see earlier emails
> why: to either supply external DC (+17, -17, 0, 48) or loop back the
> internal PSU (half the pins would carry the internal psu's voltages))
>
> That's actually pretty cool because those are small and allow a
> circular hole and are easily panel mounted. Thanks, great idea!
>
> On Mon, Jul 13, 2026 at 10:19 PM David Huss via Synth-diy
> <synth-diy at synth-diy.org> wrote:
> >
> > Ethernet has a PoE (Power-over-Ethernet) standard and in its maximum
> > PoE++ variant Type 4 switches can supply up to 100 Watts over one
> > ethernet port.
> >
> > HOWEVER: PoE similar to USB-C PD (Power Delivery) negotiates this power
> > delivery with the device attached to it and also has some measures to
> > detect faulty connections/cables. A self-baked solution may fail
> > spectacularily (and consider what happens if someone plugs your power
> > supply into an actual network port. Professional networking equipment
> > can easily cost mor than most peoples cars are worth..
> >
> > For this type of DC connection there are dedicated connectors and
> > cables. The price ranges and features vary wildly, but a good and cheap
> > solution that is tough enough for live-gig is the GX16 5-pin connector,
> > you can get a pack of 5 plugs AND jacks (including a shitty
> > screwdriver!) for 9 Euros on Amazon. The plug has a thread so it can be
> > locked and it is not too hard to solder.
> >
> > This type of plug has sometimes also be used in mixer power supplies
> > that work with outboard power supplies with exactly the requirements you
> > have, so it has been done before as well.
> >
> > Cheers,
> > David
> >
> >
> >
> > On 2026-07-13 21:24, cheater cheater via Synth-diy wrote:
> > > A little more to qualify my question, it's easier to find panel mount
> > > hardware for those, can just use a keystone plug, and they take up
> > > less space, so easier to fit on the back of a 1U device.
> > >
> > > On Mon, Jul 13, 2026 at 9:13 PM cheater cheater
> > > <cheater00social at gmail.com> wrote:
> > >>
> > >> Another question - how is everyone feeling about rj-45 as a power
> > >> plug? carrying up to 800 mA. I've seen threads where people say
> > >> they've been putting 1A through those, per pin. Thanks.
> > >>
> > >> https://www.eevblog.com/forum/projects/rj12-rj45-rj50-max-current-per-pin/
> > >>
> > >> https://groups.google.com/g/sci.electronics.design/c/TPGrRTJjReA?pli=1
> > >>
> > >>
> > >> On Mon, Jul 13, 2026 at 5:09 PM cheater cheater
> > >> <cheater00social at gmail.com> wrote:
> > >>>
> > >>> Someone off-list made some comments, and here's what came out of it:
> > >>>
> > >>> 1. All my devices use balanced audio
> > >>> 2. The rack items actually tie together their grounds by using rack
> > >>> screws and the rack rail
> > >>> 3. I don't know if the rack devices have isolated audio grounds, but
> > >>> they're almost fully analogue, except for stuff like LED bar graphs
> > >>> and on-off status LEDs for functions
> > >>>
> > >>> On Mon, Jul 13, 2026 at 4:34 PM cheater cheater
> > >>> <cheater00social at gmail.com> wrote:
> > >>>>
> > >>>> So a person on another forum mentioned that converting the devices to
> > >>>> DC input could create ground loops.
> > >>>>
> > >>>> As a reminder, I would be creating a "DC Bus" that carries +18, -18,
> > >>>> 0V, and +48V, and I would wire it in a daisy-chain configuration going
> > >>>> from unit to unit. All of those units are in one rack on top of each
> > >>>> other.
> > >>>>
> > >>>> Here's what they said:
> > >>>>
> > >>>>> If you're intending to run them all off a single raw supply, that could
> > >>>>> introduce ground loops. The safest would be a bunch of small
> > >>>>> transformers, or one with multiple secondaries. Hammond 229 are
> > >>>>> small low profile transformers that could fit in a 1U cabinet.
> > >>>>
> > >>>> So I've been thinking about this since they mentioned ground loops.
> > >>>> Here's what I think.
> > >>>>
> > >>>> Currently all those rack devices already use a three-prong IEC C14
> > >>>> receptacle, with the earth wire connected to the chassis.
> > >>>>
> > >>>> Instead of the chassis grounding point being connected via the C14
> > >>>> receptacle, and through a mains cable, to mains earth, it would now be
> > >>>> connected via my DC bus cable, which would have an earth conductor as
> > >>>> well.
> > >>>>
> > >>>> So in terms of ground loops, not much changes.
> > >>>>
> > >>>> However, given that we're talking about LOOPS, the area of the ground
> > >>>> loop would be important as well.
> > >>>>
> > >>>> Currently each rack has a cable going to a power strip.
> > >>>>
> > >>>> However, with my DC bus, I would be daisy chaining it, so the bus goes
> > >>>> to the bottom rack mount device, there's a plug there, then from that
> > >>>> plug there's a short cable going 1U above it, and so on.
> > >>>>
> > >>>> That would create an extremely small area for the devices to create
> > >>>> ground loops.
> > >>>>
> > >>>> I could (and maybe should) additionally put an earthed shield around
> > >>>> these wires, in order to shield them from EMI.
> > >>>>
> > >>>> So in total, either nothing changes regarding ground loops, or it's
> > >>>> purely improved compared to the current situation.
> > >>>>
> > >>>> I would be interested in everyone's thoughts on this matter.
> > >>>>
> > >>>> Thanks.
> > >>>>
> > >>>>
> > >>>> On Fri, Jul 10, 2026 at 6:03 PM cheater cheater
> > >>>> <cheater00social at gmail.com> wrote:
> > >>>>>
> > >>>>> there's one that's particularly noisy, but there are others that are a
> > >>>>> little noisy too, and it adds up. plus the heat just makes the room
> > >>>>> uncomfortable to be in. I've gone to great lengths to move all heat
> > >>>>> and noise generating equipment out of my day room, including moving
> > >>>>> the pcs to another place and connecting everything via fiber optics.
> > >>>>> so having 80W less heating my head will be an improvement once more.
> > >>>>>
> > >>>>> On Fri, Jul 10, 2026 at 5:58 PM el macaco <elmacaco at hotmail.com> wrote:
> > >>>>>>
> > >>>>>> Is the noisey transformer just one unit?  Would a torroidial transformer have less physical noise?
> > >>>>>>
> > >>>>>> Or if it is vibration related maybe mounting it with rubber washers and making the electrical contact with wires?
> > >>>>>>
> > >>>>>> Or move the units away from where the mic can pick up the noise?
> > >>>>>>
> > >>>>>> Not my area of expertise, just wondering if there may be a simpler solition.
> > >>>>>>
> > >>>>>> Ed
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>> Get Outlook for iOS
> > >>>>>> ________________________________
> > >>>>>> From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Ben Stuyts via Synth-diy <synth-diy at synth-diy.org>
> > >>>>>> Sent: Thursday, 09 July 2026 17:39:07
> > >>>>>> To: cheater cheater <cheater00social at gmail.com>
> > >>>>>> Cc: synth-diy <synth-diy at synth-diy.org>
> > >>>>>> Subject: Re: [sdiy] Converting rack mount to DC input?
> > >>>>>>
> > >>>>>> You could use both rails, i.e. connect the relay coil between the + and - supply. Not + and gnd. If you want anything more fancy you should build some sort of power-good circuit. But that applies to your homebrew connector solution too.
> > >>>>>>
> > >>>>>> Just look at any general purpose or small power relays from e.g. Panasonic, Omron, TE. They usually have an endurance of millions of cycles. A quick search on digikey shows lots of options, starting at a few euro’s.
> > >>>>>>
> > >>>>>> Ben
> > >>>>>>
> > >>>>>>> On 9 Jul 2026, at 18:23, cheater cheater <cheater00social at gmail.com> wrote:
> > >>>>>>>
> > >>>>>>> Thanks. A few questions:
> > >>>>>>>
> > >>>>>>> What if only some of the rails are connected, but not the one used for
> > >>>>>>> steering the relay (a fault)?
> > >>>>>>>
> > >>>>>>> Relays are kind of expensive, how much do you think that could end up costing?
> > >>>>>>>
> > >>>>>>> If they don't get cycled a lot at all, wouldn't they end up getting stuck?
> > >>>>>>>
> > >>>>>>> On Thu, Jul 9, 2026 at 5:57 PM Ben Stuyts <ben at stuyts.nl> wrote:
> > >>>>>>>>
> > >>>>>>>> You could use an internal relay for the switch-over. If there is power on the DC connector -> switch over. Otherwise keep the AC rectifier connected.
> > >>>>>>>>
> > >>>>>>>> Ben
> > >>>>>>>>
> > >>>>>>>>> On 9 Jul 2026, at 16:06, cheater cheater <cheater00social at gmail.com> wrote:
> > >>>>>>>>>
> > >>>>>>>>> In order to provide the bridging functionality it has to have at least 8 pins.
> > >>>>>>>>>
> > >>>>>>>>> On Thu, Jul 9, 2026 at 1:41 PM Ben Stuyts <ben at stuyts.nl> wrote:
> > >>>>>>>>>>
> > >>>>>>>>>> Perhaps a 4 or 5 pin XLR connector is an option? They are not that expensive, and lots of ready-made cables are available.
> > >>>>>>>>>>
> > >>>>>>>>>> Ben
> > >>>>>>>>>>
> > >>>>>>>>>>> On 9 Jul 2026, at 10:18, cheater cheater via Synth-diy <synth-diy at synth-diy.org> wrote:
> > >>>>>>>>>>>
> > >>>>>>>>>>> One way to have DC input, but retain the capability of using the
> > >>>>>>>>>>> internal power supply, is to have a 4P2T switch for configuration.
> > >>>>>>>>>>>
> > >>>>>>>>>>> It seems that 4P2T switches are super expensive, especially if they're
> > >>>>>>>>>>> supposed to withstand, say, 1A.
> > >>>>>>>>>>>
> > >>>>>>>>>>> So I started looking around. TLDR: classic pcie 8-pin power connectors
> > >>>>>>>>>>> are probably the best, and also the cheapest.
> > >>>>>>>>>>>
> > >>>>>>>>>>> My first thought was to look at PCIE x1 slots. The cheapest advanced
> > >>>>>>>>>>> connector on earth, for 0.4 Euro at unit price, you get a connector
> > >>>>>>>>>>> that handles 1.1A per pin as per eg this document, page 6, 4.4
> > >>>>>>>>>>>
> > >>>>>>>>>>> https://cdn.amphenol-cs.com/media/wysiwyg/files/documentation/gs-12-233.pdf
> > >>>>>>>>>>>
> > >>>>>>>>>>>> 4.4 CONTACT CURRENT RATING
> > >>>>>>>>>>>> 1.1 amp per contact minimum per EIA-364—70, method 2 and PCI Express Connector High Speed Electrical Test Procedure. The temperature rise shall not exceed 30 degree C. Ambient condition is still air at 25°C.
> > >>>>>>>>>>>
> > >>>>>>>>>>> The connector has 36 pins, so while I don't think it would handle 36A,
> > >>>>>>>>>>> I'm sure it would handle something like 2A, especially if you share
> > >>>>>>>>>>> pins. You can even leave pins empty to prevent shorts during
> > >>>>>>>>>>> insertion.
> > >>>>>>>>>>>
> > >>>>>>>>>>> You could put the connector out the back, and either insert a plug-in
> > >>>>>>>>>>> "card" (really just a small edge connector with wires soldered on)
> > >>>>>>>>>>> that provides DC, or a pass-through "card" that shorts some pins
> > >>>>>>>>>>> together to carry power from the internal power supply. And now
> > >>>>>>>>>>> instead of $20-30 per unit, this costs $1 per unit. My main question
> > >>>>>>>>>>> is how I would fix the connector, but maybe a simple screw hole in the
> > >>>>>>>>>>> connector that mates with a threaded hole in the case could do the
> > >>>>>>>>>>> trick.
> > >>>>>>>>>>>
> > >>>>>>>>>>> A pcie x1 port is 25mm long, so it can fit upright in the back of a 1U
> > >>>>>>>>>>> rack unit, which is 45mm, so it doesn't take up much space either.
> > >>>>>>>>>>>
> > >>>>>>>>>>> The cheapest one that can be found at Mouser currently and can be
> > >>>>>>>>>>> bought in low volumes is roughly 0.4 Euro.
> > >>>>>>>>>>>
> > >>>>>>>>>>> https://www.mouser.at/ProductDetail/Amphenol-FCI/10018783-10200TLF?qs=V%252BXmToedwojeZUI4fPwmPA%3D%3D
> > >>>>>>>>>>>
> > >>>>>>>>>>> Qty.  Unit Price  Ext. Price
> > >>>>>>>>>>> 1     € 0,439     € 0,44
> > >>>>>>>>>>> 10    € 0,372     € 3,72
> > >>>>>>>>>>> 25    € 0,332     € 8,30
> > >>>>>>>>>>> 100   € 0,316     € 31,60
> > >>>>>>>>>>>
> > >>>>>>>>>>> By making the connector require a dummy plug to connect the internal
> > >>>>>>>>>>> power supply into the circuit, it makes it impossible to connect both
> > >>>>>>>>>>> DC power and mains AC, so that makes the design intrinsically safe
> > >>>>>>>>>>> without using switches.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Alternatively to a PCIE connector I could use some panel mount plug
> > >>>>>>>>>>> with 8 pins, have 4 pins for DC input, and have the other 4 pins carry
> > >>>>>>>>>>> power from the internal power supply, and similarly use a shorting
> > >>>>>>>>>>> plug to use the internal power supply.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Circular DIN connectors start at about 8 Euro per pair of socket and plug.
> > >>>>>>>>>>> Circular metric aren't better.
> > >>>>>>>>>>> MIL Spec connectors seem to be cheaper. But the mouser search sucks,
> > >>>>>>>>>>> so I can't find them by number of pins.
> > >>>>>>>>>>>
> > >>>>>>>>>>> PCIE 8-pin power connectors are real, real cheap - 10 cents a piece.
> > >>>>>>>>>>> They're latching (no need for screws and stuff). There doesn't seem to
> > >>>>>>>>>>> be a panel mount version, but one could mount a through-hole connector
> > >>>>>>>>>>> to a pcb, and have the pcb have screw holes for mounting to the rear
> > >>>>>>>>>>> panel. They handle high power - 150W meaning 3A per pin (half the pins
> > >>>>>>>>>>> are return pins). Seems like a winner to me. They're also tiny so they
> > >>>>>>>>>>> will easily fit in the back of a 1U unit even vertically. The biggest
> > >>>>>>>>>>> pain here might be making the rectangular hole and having it look any
> > >>>>>>>>>>> good. might be a case for custom die, maybe a small steel job that
> > >>>>>>>>>>> uses two bolts to screw together the two cutting parts through the
> > >>>>>>>>>>> sheet metal.
> > >>>>>>>>>>>
> > >>>>>>>>>>> "Pin and socket" connectors are the same kind of thing, just not
> > >>>>>>>>>>> specifically PCIE 8-pin. Still cheap at roughly 20 cents a piece...
> > >>>>>>>>>>> useful alternative if more than 4 rails are necessary.
> > >>>>>>>>>>>
> > >>>>>>>>>>> D-sub connectors carry up to 3A... and are very cheap and can do panel
> > >>>>>>>>>>> mount of some sort. But I'll be damned if I use one of those cursed
> > >>>>>>>>>>> things for power.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Automotive connectors seem inexpensive too, but I haven't really
> > >>>>>>>>>>> looked into them much other than a quick parametric search.
> > >>>>>>>>>>>
> > >>>>>>>>>>> I wonder what everyone thinks of this.
> > >>>>>>>>>>>
> > >>>>>>>>>>> On Tue, Jul 7, 2026 at 6:39 AM cheater cheater
> > >>>>>>>>>>> <cheater00social at gmail.com> wrote:
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> Don't you think this may have had something to do with you
> > >>>>>>>>>>>> distributing AC power, rather than DC with 0V potential?
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> On Sat, Jul 4, 2026 at 11:33 PM Mattias Rickardsson <mr at analogue.org> wrote:
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> Den lör 4 juli 2026 14:23Florian Anwander via Synth-diy <synth-diy at synth-diy.org> skrev:
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> Maybe, it's a stupid thought, but...: could it be that a device relies on beeing galvanical separated from other devices. I this case the common supply might clash with the devices concept.
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> This reminds me of a somewhat similar issue I had many years ago:
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> I wanted a Korg MS-20 and a Korg KR-55 to share one external power puck. (Swedish-sold old Korgs had a big external power transformer to step down from 220 V AC to 16 V AC, which is then what the instrument then accepts via a plug with 2 flat prongs that doesn't seem roadworthy with European electrical standards.)
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> So I made a short splitter Y cable on the 16 V AC side and attached both instruments and turned them on. But then I connected an audio cable between them (or audio cables from both units to the same mixer) and I had a blown fuse! It was apparently not okay to connect those two grounds together when running off the same AC supply.
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> /mr
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> ________________________________________________________
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> > >>>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>>
> > >>>>>>>
> > >>>>>>
> > >>>>>>
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