m50 60-cycle hum problems?

michaelm33 · Post by **michaelm33** » Thu May 26, 2011 8:21 pm

I just bought 2 m50's and both have major 60-cycle hum noise when I connect the L/MONO output to any amp. I did all the normal troubleshooting (changed cables, amps, etc.). None of my other synthesizers or keyboards do this (using the same cables and amps).

Any ideas as to the cause? My old TR61 never did this either.

kimu · Post by **kimu** » Thu May 26, 2011 9:22 pm

have you tried balanced cable also?

you have the problem whenever you plug the PUS? i mean have you tried in other houses or rehearsal room?

DoctorMo · Post by **DoctorMo** » Thu May 26, 2011 9:26 pm

Are both the keyboard and the amp on the same AC circuit? If not, try putting them together in the same power strip.

mike

billbaker · Post by **billbaker** » Fri May 27, 2011 1:10 pm

The hum is 99% a grounding problem.

Things to try:

Ground lift (changes 3 prongs to two).

"Conditioned" power - usually these units have circuitry to eliminate the ground problems, and sometimes to let you know when they're there.

(prev post) Same power for keys and amp - should be SOP for gigs and studio set-ups.

Direct box with ground lift for signal path - you may be able to fix the audible problem without fixing the source of the problem directly - that's enough for some folks.

Depending on amp, you may have issues with mic vs line level signal strength - get advice on the send levels and gain at the amp - setting it correctly has a big impact on signal to noise ratio.

Make sure you are not using speaker, vs instrument cables - they look pretty much the same, but speaker cables may cause similar noise.

BB

dgk89 · Post by **dgk89** » Tue Apr 16, 2013 6:44 am

I also have an M-50 with a very noticeable and annoying hum. Tried all the usual fixes but no luck. I have a Yamaha Motif XS8 and two Roland JV880's in the same midi loop and they have no hum at all.

I like the machine but can't use it for recording with this problem. I will keep experimenting. Haven't tried the old three prong into two trick yet but its worth a try. I will report back with results if any.

Yatrix · Post by **Yatrix** » Tue Apr 16, 2013 7:23 am

Hum could be due to bad power supply unit.
I had similar issue with audio on my notebook.
After replacing power supply the annoying hum disappered completely .

So, try to replace it by any unit with 18 stabilized voltage and see what happens.
If it works then the original power supply should be changed by warranty.
Normally there should not be any hum issue never matter on condition of outlets, grounding or voltage fluctuations in power network.

dgk89 · Post by **dgk89** » Wed Apr 17, 2013 6:42 am

Something interesting about the mysterious hum coming from my Korg M-50 is that turning the volume down to zero on either the Korg or the mixing board that it is plugged into does not affect the hum. The only way to stop the hum is to turn the machine off or kill the volume on the amplifier.

If I just plug a pair of headphones into the headphone jack and don't use any external amplification there is no hum! At least in the headphones anyway. That is why I first assumed it was a bad cable or possibly a bad channel in the mixing module. I just didn't think it could be a problem with the synth.

The dealer that I bought the unit from does not have an in house repair service or I would have taken it in by now.

Ajbbklyn · Post by **Ajbbklyn** » Wed Apr 17, 2013 12:44 pm

Refer to Bill Baker's post from 2011. This is almost certainly caused by improper grounding.

Bartholomey · Post by **Bartholomey** » Fri Dec 02, 2016 3:48 am

Isolate the problem by first turning off computer monitors or other electrical equipment in the area. I have a Samsung monitor that causes my M3 to produce a loud hum. Make certain the M3 still has a hum present when no other equipment is on.