yamaha p155: HELP! midi out adding noise to aux audio out

[Drew Boles]

hey everybody -
I've been trying to figure out why the auxiliary audio out on my yamaha p-155 keyboard was exhibiting strange hum/noise over sounds of my playing. i eventually discovered that the culprit is the midi out - if i have it connected to the midi in of an interface, it adds an annoying buzz/hum to the audio coming from aux out. has anybody experienced this before? i'm curious about what a solution might be. thank you

 

[The Y_man]

I think some sort of earthing issue.... (there's likely a piece of cricuitry contacting the chassis)

The Y-man

 

[Drew Boles]

Thank you for your response. Pardon my technical ignorance, but I assume this circuitry issue you're positing is something internal with the keyboard and would have to be repaired? Or would there be other ways to handle this that doesn't require surgery, so to speak? Thanks again!

 

[The Y_man]

Unfortunately it's likely to require opening up the unit, and having a good look around...does the unit get taken to gigs, or live quietly at home?

The Y-man

 

[Drew Boles]

well, the intention is to take it to gigs, but i've had the keyboard for only a few months, and the gigging hasn't started yet. so right now, just quietly at home, but that will change very soon. unfortunately, i need a fix because my setup requires using both the midi out and aux out on the keyboard.

 

[Drew Boles]

ps if it's a matter of circuitry touching the chassis, is this something i could theoretically open up and check out myself? or does that void the warranty if you do that?

 

[YeahDoIt]

I'm wondering if it is the cable or the interface that is introducing hum. If you disconnect the interface but keep the cable plugged into the keyboard do you still hear hum?

 

[Drew Boles]

That's a good question. I have 3 interfaces that I tested this on: Motu Ultralite mk3, Digi 002, and Edirol FA-101. The Motu and Digi racks both produced this hum. The Edirol only does if I connect a MIDI out to another MIDI out. I also notice that if I plug the MIDI into a USB device with standard MIDI ins, it does not seem to create this problem. So, it seems that perhaps you are correct - there's something about the interface(s) - or at least the connection they form with the Yamaha - that's generating this problem. Any ideas what this is? I'm wondering if I should just get a little USB MIDI interface and forego the on-board MIDI, since it seems to be giving me grief. Any other ideas?

 

[Drew Boles]

one thing i also noticed is that if i'm connected to one interface - the Motu for instance - and I plug the MIDI out from the yamaha into the Digi interface (even if it's turned off), I get the same hum. it's so strange, i have no idea what's going on

 

[The Y_man]

...does that void the warranty if you do that?

Hang on, it has warranty? I'd say send it back....

The Y-man

 

[DickR]

Sounds indeed like an earthloop or similar problem as the Y-Man suggested.
Long distance guessing off course.
My strong advice DON'T open your unit if it is still under warranty and if not do it ONLY when you know what you are doing an looking for.
Check this first:
Do you use different wall outlets to feed your equipment?
If so, you might use two different circuits of your home-powersupply, try to use only one with a powerboard wirh a few outlets and plug in one by one your equipment if applicable until you get this buzz. The piece that gives the buzz is most likely the bandit. If pos reverse the plug of that one or rewire it in reverse.
You said somewhere 'midi out to midi out' that's not working or you made a typo perhaps?
Do NOT place speakers near your sound cables or have cables laying over powersupplies etc. Use ONLY good quality shielded cables.
No mobilphone or wireless, airco or similar near your cables. Notorious for picking up distorsion.
My two cents for today, I hope you can solve it.

Regards
DickR

 

[YeahDoIt]

I wonder if the MIDI cable is not grounded. I would swap cables with a known good one.

Is there a Yamaha service center near you?

 

[Oyst3h]

The MIDI spec requires that all MIDI IN ports are opto-isolated, So it should in theory be impossible to introduce a ground loop via MIDI (USB ports do not have the same requirement, and the Int4rw3bz are full of people complaining about hums and buzzes when using USB-MIDI).

If you're getting a ground loop using a standard MIDI connection (5-pin DIN cable), from the MIDI OUT of your Yamaha P155 to the MIDI IN of another device then the other device is faulty - NOT the Yamaha.
The fact that your Edirol device only hums when you connect the MIDI OUT to MIDI OUT backs this up, since MIDI OUTs are not opto-isolated.

It is slightly strange, however, that two devices both exhibit the same problem - particularly since they are both from manufacturers that I would normally consider to be reliable.