[sdiy] Prophet 5 weirdness.

Sarah Thompson plodger at gmail.com
Mon Mar 14 21:56:05 CET 2016


It's always a good idea to run all your equipment from a single outlet,
ideally with a tree structure of power adapters rather than a chain. This
keeps any ground loops as small as possible. You may even have a case where
you have two sockets that are run from different phases -- don't do it!
Audio gear is rarely as well everything-proofed electrically as we'd like.

Sarah

On Mon, Mar 14, 2016 at 1:19 PM, Dave Magnuson <abide at dmdrafting.com> wrote:

> I would certainly investigate the power first.    I had some interesting
> noises / zaps from older gear (in particular) when they were powered from
> two different circuits.
>
>
>
> First, unplug both racks and confirm voltage / neutral / ground on your
> two receptacles
>
>
>
> Next, I’d measure voltage from hot-to-hot, neutral-to-neutral and
> ground-to-ground on the two receptacles.   Be aware you could have a 240V
> differential, so set your meter accordingly.
>
>
>
> Next,  disconnect the audio cable, power up both racks.   Measure voltage
> chassis-to-chassis between both racks, then audio ground-to-audio ground on
> both racks
>
>
>
> After that, run all that gear from one outlet and see if plays nicely
>
>
>
> That should help diagnose where the problem actually lies
>
>
>
> Dave Magnuson
>
>
>
> *From:* Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl] *On Behalf
> Of *Jim Blair
> *Sent:* Monday, March 14, 2016 4:03 PM
> *To:* synth-diy at dropmix.xs4all.nl
> *Subject:* [sdiy] Prophet 5 weirdness.
>
>
>
> Hi all. Thanks in advance for your help!
>
>
>
> I have a Prophet 5 rev 3.3, which someone in the distant past converted
> into a brain-only format. So, no keyboard. Midi only. It's now happily
> residing in the lower row of a modular. It works great, and sounds amazing.
> The PSU has been recapped, and new regulators installed. All is well.
>
>
>
> Almost.
>
>
>
> Get this. When I plug the audio out into a guitar amp or a pedal, the
> synth works great. But when I plug it into my API preamp, or Sansamp rack
> unit, the synth loses it's mind. All the front panel lights start
> flickering, and the output is all loud and nasty noises.
>
>
>
> I think that the Sansamp and API are both plugged into a different AC
> house-circuit than the P5, but I'm not sure of this yet. More investigation
> is required. I run other synths, both modern and vintage, into the Sansamp
> and API all day long, and have never experienced a problem.
>
>
>
> Thoughts?
>
>
>
>
>
> Jim
>
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>
>


-- 
[s]
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