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Jason_R
Supreme tranceaddict

Registered: Feb 2004
Location: High Wycombe

Synth Ground loop / Hum

Hi Guys

Today at long last I added a roland JP8080 to my studio ( well bedroom! )

While it's doing everything I expected it to there seems to be an anoying problem with it seemingly producing a ground loop / hum ( you know that noise you usally get when setting up decks )

I've had a look at a few tutorials on the net and they all suggest that it's the source of this problem is usally in the power supply.

This is where it's confusing me as the power supply I'm using is for My Novation Ks rack and when using that synth there is no hum what so ever.

I run these synths through a mixer ( Soundcraft compact 10 ) so I thought mabey this is where the problem is but it clearly isn't ( I tested it by hooking up my access virus c which has a diffrent power supply altogether and no hum at all )

While I track down what's causeing this is it possible for the synth it's self ( jp8080 ) to be produceing the hum or does the problem most likley lie else where??

Many thanks for you suggestions.

Feb-01-2007 22:56 United Kingdom

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echosystm
super wow maker

Registered: Jul 2004
Location:

I honestly don't have any idea about this... but to me it would sound logical to ground everythign to your mixer and get a ground loop isolator or two.

Feb-02-2007 00:04 Australia

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DigiNut
You kids get off my lawn!

Registered: Dec 2002
Location: Toronto, Self-proclaimed Centre of the Universe

It's possible, but you have to use process of elimination here rather than asking us. It doesn't mean anything that the power supply doesn't produce hum on a different synth, or that you can run a different synth through the mixer without getting hum.

First plug your JP directly into your monitors. See if you hear hum. If you still hear it, try a different power supply. If you still hear it after that, it could very well be a problem with the JP.

If you hear no noise when you plug it into the monitors, then it's picking something up on the way into/out of the mixer. Are you using good shielded cables?

Start from there, let us know what you find.

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Feb-02-2007 01:09 Canada

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camsr
Suspended User

Registered: Sep 2006
Location: nor cal

IS the power plug for the jp grounded or two prong?

Also try shielded cables, as mentioned. The shorter the cable the better.

If it's truely the power supply's fault, it could be a blown filtering capicitor but I doubt it's that severe (probably because the whole thing would act wonky if it were).

If possible, plug in the synth to a completely different circuit in your house. Run an extension cord if you have to.

Good luck

Feb-02-2007 05:38

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Derivative
Bipolar Bear

Registered: Jun 2004
Location: Dublin

If you know all your cables are shielded properly and you don't have loads of electrical appliances nearby with poorly shielded power supplies then you can break a ground loop using a Direct Injection box. JP8080 has a stereo output so you would need a stereo DI box. They range from the super cheap (less than a tenner) to the quite expensive (couple hundred quid) but they all output balanced and they all break ground loops.

Feb-02-2007 10:36 Ireland