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.