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Hum / Noise from Mono/Poly

2016-10-28 by yanbuster@gmail.com

Hi All,

I have Mono/Poly that is creating some hum from the main output. I am not getting the hum when connected to the headphone jack however, or at least it is barely audible. For some background on my connections, I am using 6' new 1/4" unbalanced cable into a Speck XSum mixer, and monitoring from there. I have several other synths connected that I've tested with all different cabling and power source configurations, and the Mono/Poly (and my Poly/Six) are the only two that have the hum issue. I've also tried these through my EBtech Hum Eliminator with no difference in sound.

I am guessing this might be transformer related or something similar, but wanted to reach out to the group here to get some input on what might be contributing. I would love to be able to upgrade to the MidiPolis MidiPoly kit, which appears to add a plate with a grounded NEC connector on the back. Wondering if anyone thinks this might help with the issue? I ought to just get this into a synth repair shop, but I am pretty handy with a soldering iron and schematics, I installed a Synhouse midi kit into this many many years ago. I'm about to remove that and put in a ModyPoly kit that I purchased, but thinking I might want to go the MidiPolis route instead.

Any input on the hum issue is appreciated, thanks.

Re: Hum / Noise from Mono/Poly

2016-10-29 by jw_dewdney@yahoo.com

1. Does it do this when you move it to radically different locations in your house or studio? fluorescent light ballasts in your place or next door (or even upstairs or downstairs will definitely do this. As will ground loops. But moving it around is a good way to check for RFI and ballast hum etc.

2. Does it do this when you listen via headphones straight out of the synth? if not then it's nothing to do with the synth.

3. Does the noise vary or abate when you have it opened up? Try moving some wires around etc but please make sure you did (2) first.

there are other sources of problem but these should take care of 99% of the likeliest ones.

Re: Hum / Noise from Mono/Poly

2016-10-29 by jw_dewdney@yahoo.com

so in other words - since you're not getting it on the headphone jack - time to start investigating stuff downstream from your output... swap cables - run it straight into your amplifier etc etc

Re: Hum / Noise from Mono/Poly

2016-10-29 by Rick Nicholls

I occasionally encounter the same problem with my Mono/Poly. I've discovered it is nothing wrong with the Mono/Poly but rather is down to the fact that the synth picks up ground hum from other instruments (SOMETIMES).

It all depends how many bits of gear I've got setup and how they're all wired etc

Anyhow, it can be eliminated with a simple and cheap audio isolator from Orchid Electronics (or similar)

Maybe your problem is different, but like I say, mine does it from time to time - the hum comes from the channel I'm feeding the Mono/Poly into on my desk, but is not actually generated by the synth itself - more so by the spaghetti junction of cables running around my studio :)