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The 6 pin XLR is the standard for +/- power transmission. See last entry on :</div>
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<a href="https://www.clarkwire.com/pinouts/xlr-audio-pinouts">https://www.clarkwire.com/pinouts/xlr-audio-pinouts</a></div>
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<b>From:</b> Synth-diy <synth-diy-bounces@synth-diy.org> on behalf of Ben Stuyts via Synth-diy <synth-diy@synth-diy.org><br>
<b>Sent:</b> 09 July 2026 12:40<br>
<b>To:</b> cheater cheater <cheater00social@gmail.com><br>
<b>Cc:</b> synth-diy <synth-diy@synth-diy.org><br>
<b>Subject:</b> Re: [sdiy] Converting rack mount to DC input?</div>
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<div style="font-size: 11pt;">Perhaps a 4 or 5 pin XLR connector is an option? They are not that expensive, and lots of ready-made cables are available.<br>
<br>
Ben<br>
<br>
> On 9 Jul 2026, at 10:18, cheater cheater via Synth-diy <synth-diy@synth-diy.org> wrote:<br>
><br>
> One way to have DC input, but retain the capability of using the<br>
> internal power supply, is to have a 4P2T switch for configuration.<br>
><br>
> It seems that 4P2T switches are super expensive, especially if they're<br>
> supposed to withstand, say, 1A.<br>
><br>
> So I started looking around. TLDR: classic pcie 8-pin power connectors<br>
> are probably the best, and also the cheapest.<br>
><br>
> My first thought was to look at PCIE x1 slots. The cheapest advanced<br>
> connector on earth, for 0.4 Euro at unit price, you get a connector<br>
> that handles 1.1A per pin as per eg this document, page 6, 4.4<br>
><br>
> <a href="https://cdn.amphenol-cs.com/media/wysiwyg/files/documentation/gs-12-233.pdf" id="OWA93021881-237e-0540-b40f-9bf05a8a29f4" class="OWAAutoLink" data-auth="NotApplicable">
https://cdn.amphenol-cs.com/media/wysiwyg/files/documentation/gs-12-233.pdf</a><br>
><br>
>> 4.4 CONTACT CURRENT RATING<br>
>> 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.<br>
><br>
> The connector has 36 pins, so while I don't think it would handle 36A,<br>
> I'm sure it would handle something like 2A, especially if you share<br>
> pins. You can even leave pins empty to prevent shorts during<br>
> insertion.<br>
><br>
> You could put the connector out the back, and either insert a plug-in<br>
> "card" (really just a small edge connector with wires soldered on)<br>
> that provides DC, or a pass-through "card" that shorts some pins<br>
> together to carry power from the internal power supply. And now<br>
> instead of $20-30 per unit, this costs $1 per unit. My main question<br>
> is how I would fix the connector, but maybe a simple screw hole in the<br>
> connector that mates with a threaded hole in the case could do the<br>
> trick.<br>
><br>
> A pcie x1 port is 25mm long, so it can fit upright in the back of a 1U<br>
> rack unit, which is 45mm, so it doesn't take up much space either.<br>
><br>
> The cheapest one that can be found at Mouser currently and can be<br>
> bought in low volumes is roughly 0.4 Euro.<br>
><br>
> <a href="https://www.mouser.at/ProductDetail/Amphenol-FCI/10018783-10200TLF?qs=V%252BXmToedwojeZUI4fPwmPA%3D%3D" id="OWA885bdfdd-23aa-02c6-1e92-5f656d1b7e80" class="OWAAutoLink" data-auth="NotApplicable">
https://www.mouser.at/ProductDetail/Amphenol-FCI/10018783-10200TLF?qs=V%252BXmToedwojeZUI4fPwmPA%3D%3D</a><br>
><br>
> Qty. Unit Price Ext. Price<br>
> 1 € 0,439 € 0,44<br>
> 10 € 0,372 € 3,72<br>
> 25 € 0,332 € 8,30<br>
> 100 € 0,316 € 31,60<br>
><br>
> By making the connector require a dummy plug to connect the internal<br>
> power supply into the circuit, it makes it impossible to connect both<br>
> DC power and mains AC, so that makes the design intrinsically safe<br>
> without using switches.<br>
><br>
> Alternatively to a PCIE connector I could use some panel mount plug<br>
> with 8 pins, have 4 pins for DC input, and have the other 4 pins carry<br>
> power from the internal power supply, and similarly use a shorting<br>
> plug to use the internal power supply.<br>
><br>
> Circular DIN connectors start at about 8 Euro per pair of socket and plug.<br>
> Circular metric aren't better.<br>
> MIL Spec connectors seem to be cheaper. But the mouser search sucks,<br>
> so I can't find them by number of pins.<br>
><br>
> PCIE 8-pin power connectors are real, real cheap - 10 cents a piece.<br>
> They're latching (no need for screws and stuff). There doesn't seem to<br>
> be a panel mount version, but one could mount a through-hole connector<br>
> to a pcb, and have the pcb have screw holes for mounting to the rear<br>
> panel. They handle high power - 150W meaning 3A per pin (half the pins<br>
> are return pins). Seems like a winner to me. They're also tiny so they<br>
> will easily fit in the back of a 1U unit even vertically. The biggest<br>
> pain here might be making the rectangular hole and having it look any<br>
> good. might be a case for custom die, maybe a small steel job that<br>
> uses two bolts to screw together the two cutting parts through the<br>
> sheet metal.<br>
><br>
> "Pin and socket" connectors are the same kind of thing, just not<br>
> specifically PCIE 8-pin. Still cheap at roughly 20 cents a piece...<br>
> useful alternative if more than 4 rails are necessary.<br>
><br>
> D-sub connectors carry up to 3A... and are very cheap and can do panel<br>
> mount of some sort. But I'll be damned if I use one of those cursed<br>
> things for power.<br>
><br>
> Automotive connectors seem inexpensive too, but I haven't really<br>
> looked into them much other than a quick parametric search.<br>
><br>
> I wonder what everyone thinks of this.<br>
><br>
> On Tue, Jul 7, 2026 at 6:39 AM cheater cheater<br>
> <cheater00social@gmail.com> wrote:<br>
>><br>
>> Don't you think this may have had something to do with you<br>
>> distributing AC power, rather than DC with 0V potential?<br>
>><br>
>> On Sat, Jul 4, 2026 at 11:33 PM Mattias Rickardsson <mr@analogue.org> wrote:<br>
>>><br>
>>> Den lör 4 juli 2026 14:23Florian Anwander via Synth-diy <synth-diy@synth-diy.org> skrev:<br>
>>>><br>
>>>> 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.<br>
>>><br>
>>><br>
>>> This reminds me of a somewhat similar issue I had many years ago:<br>
>>><br>
>>> 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.)<br>
>>><br>
>>> 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.<br>
>>><br>
>>> /mr<br>
>>><br>
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