[sdiy] Prophet 5 weirdness.

Dave Leith dave.leith at gmail.com
Mon Mar 14 22:29:41 CET 2016


I run my Prophet 5 into an API channel strip and no problems there (DI
input)

On Mon, Mar 14, 2016 at 1:56 PM, Sarah Thompson <plodger at gmail.com> wrote:

> 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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