[sdiy] power cables

rburnett at richieburnett.co.uk rburnett at richieburnett.co.uk
Fri Aug 16 11:34:45 CEST 2019


Make sure you keep the DC power wiring away from the mains transformer 
and it's AC wiring.  Otherwise any leakage field from the transformer 
and around the wires carrying AC from it's secondary winding can induce 
hum into your nice clean DC supply wiring.

-Richie,



On 2019-08-16 05:43, Youssef Menebhi wrote:
> Thanks for the suggestions so far - I poked around a bit and it helped
> to know what you would have considered.
> Having taken a closer look, I noticed that the hum was definitely
> originating with the power supply. I tightened up the screws on the
> transformer, which improved things about 50%. Still, oddly, the
> thinner gauge cable seems to produce less hum.  I'm pretty certain
> it's not a ground loop issue, at this point - since I've tried
> multiple modules, independently.
> 
> On Thu, Aug 15, 2019 at 11:26 PM Oren Leavitt <obl64 at ix.netcom.com> 
> wrote:
>> 
>> 
>> On 8/15/19 9:45 PM, Youssef Menebhi wrote:
>> > Hi everybody,
>> >
>> > I've been building my own circuits for a little while now and have
>> > just switched to a new power supply/connector arrangement. I use
>> > bipolar power, plus and minus 12v.  What I've noticed, though, is that
>> > when I use headphone cable (shielded ground) to pass power, I get a
>> > small hum at the output. When I use even thinner gauge cable, I don't
>> > get hum. Unfortunately, it's hard to get a hold of the ultra-thin
>> > gauge cable.  Am I out of luck? Does anyone have any idea why this
>> > might be happening?
>> > _______________________________________________
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>> >
>> 
>> Hi Youssef,
>> 
>> Sounds like you may have a ground loop somewhere. It may be that the
>> thinner cable has enough internal resistance to break the loop. If you
>> can track down the source of the loop and fix it, you'll leave 
>> yourself
>> free to use heavier gauge wire for the power connections.
>> 
>> May two bits
>> 
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