Hi I have a stage piano with balanced outs and i've rigged up a small balanced cable run so I can plug it in, to record with ease. However there's some signal degradation and a hum going on. The piano has a ground lift switch but this doesn't totally alleviate the problem - the hum is still decidedly there. So my question is:

Let us assume for a moment it's a ground loop - are there any simple fixes I'm missing? I've tried running an extension from a common plug over to the piano but this doesn't help.

I was looking at DI boxes and was also wondering if a small mixer (which I'm looking to buy anyway) would help boost the signal to line level at the keyboard side?

Please, any suggestions and recommendation would be very much appreciated. DI boxes seem sooo expensive, so any good cheap ones for the studio would be useful to know.

Thanks in advance.
Tony

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If your piano does have proper balanced outs then you probably have the 'pin 1' problem somewhere and need to cut pin 1 on one end of your XLR leads (or the sleeve connection if you use TRS), or get the adapters mentioned in the ground loop thread currently running in this forum. Hugh goes into all the physics fsr better than I could, so have a read and see what you think.

If on the other hand, they're not actually proper balanced outputs then get a good DI as you'll need it sooner or later. What exactly is your keyboard? Somebody here should be able to tell you the best solution if you let us know the make and model.

I may have oversimplified the problem here but if you read Kolacube's 'Ground loop ghost' thread you'll know a fair bit more about it.

In addition to the information tacitus has suggested you provide, it would also be helpful to know a bit more about the interconnect cable you've made up - ie plugs on each end and how you've inter-connected them.

Ground lift switches are provided specifically to cure ground loops, and if the switch doesn't fix it on your system them something else is going on elsewhere in the system.

Hums can be caused by things other than ground loops. EM induction into the cable is a possibility if it runs near mains leads or strong transformers in equipment.

It would help to know the make/type of piano, the recorder, and details of your cable.

Hugh

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Technical Editor, Sound On Sound

Thank you all for your kind answers. The piano is a Kawai MP8 MK1. The cable is standard xlr male to female going into an edirol UA-25 interface. I had also wondered about induction... as the cable run is shared by a USB Active repeater extension to the piano, for easy midi.

OK just troubleshooted a bit. The Hum is in one channel, and both channels hiss noticeably. I removed the active repeater cable and pulled the cables away from the wall and the hum/hiss was still there. So I bypassed the Edirol UA25 interface and plugged the xlrs straight in my monitors... hum/hiss gone! So it's the USB interface that seems to be the root cause.

It may be completely unconnected, but I have noticed some audio ghosting when I record from the UA-25 xlr ins recently, but attributed it to bad cable or mic. It seems intermittent though. Maybe I've uncovered a fault? If so, bugger.

Please, any suggestions regarding the cause of, and possible solution for, this problem would be greatly appreciated, plus troubleshooting suggestions.

Thanks once again,
Tony

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The Kawai MP8 has true balanced outputs and is a properly robust bit of kit which I love working with. The xlr outs do not need to be di'd: any mixer will handle them just fine as they are.

I would try another set of xlrs, separate from your new cable run, and see if the problem persists. You could always try the (unbalanced) jack outs as well: if your setup is relatively simple, the gains from using xlr outs are relatively small. In the anticipated noisy stage environment that these pianos are designed for, another matter...

Any suggestions? Am I flogging a dead horse here???

Oh, the kawai is a proper instrument I love it - and since I modded the keys to give a slightly lighter action I am very happy with it. Although it's always lacked the 'immediacy' of some digi pianos, some of which are much cheaper. But for meaningful, weighty playing playing this piano really is the best. I can do everything else on it too - but there are pianos out there which suit fast ragtime or mozart a little better.

BUT what am I doing? this isn't a review! And I've never had any issues with the XLRs, it's actually quite unusual to have them on pianos so am grateful for that.

T

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Quote maskedwarrior:

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Thank you all for your kind answers. The piano is a Kawai MP8 MK1. The cable is standard xlr male to female going into an edirol UA-25 interface. I had also wondered about induction... as the cable run is shared by a USB Active repeater extension to the piano, for easy midi.

OK just troubleshooted a bit. The Hum is in one channel, and both channels hiss noticeably. I removed the active repeater cable and pulled the cables away from the wall and the hum/hiss was still there. So I bypassed the Edirol UA25 interface and plugged the xlrs straight in my monitors... hum/hiss gone! So it's the USB interface that seems to be the root cause.

It may be completely unconnected, but I have noticed some audio ghosting when I record from the UA-25 xlr ins recently, but attributed it to bad cable or mic. It seems intermittent though. Maybe I've uncovered a fault? If so, bugger.

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What does "audio ghosting" mean? This sounds more like a monitoring loop getting somewhere it shouldn't.

How does the piano behave with its unbalanced jacks connected to the Edirol? I think the balanced outputs bypass master level on the piano? Using the unbalanced outs (which do go through the master control) might make it easier to optimise the gain structure?

'Audio ghosting' was meant to describe the sound produced on vocals I've notice, recorded using the XLR ins on the edirol UA-25. Sort of like a muffled, lower range 'ghost' of what's sung.

I thought at the time it was the mic cable or mic - but now I'm not so sure.... I think I need to go trouble shoot some more

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HI I thought I'd update this.

I've figured out the Electric Piano noise problem, in that there may not have been a problem in the first place! Basically I had got into the habit of forgetting some signal chain basics... I simply turned down the input gain on my interface as much as I could and turned up the gain on the piano out to compensate and I was left with a very healthy signal to noise ratio.

Probably I'm an idiot. But thought I'd share in case someone struggles as much as me to achieve simple things.

As far as the vocal 'ghosting' I described is concerned I haven't recorded vocals since but this may be a separate problem and could well have been a bad lead...

Will let you know about this!
Thanks very much.
Tony

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Tony, I guess most of us have been there (many times, if I'm at all typical). Once you've convinced yourself one thing is true, it's very hard to come to terms with a different interpretation of the situation. I've got to the point where as soon as this sort of problem arises I sit back and think of all the stupid things I might have done, and it's amazing how often I can fix it by unmuting the channel or even plugging the cable into the right input. I like to think I set up methodically, but there are nearly always interruptions and even without them it's so easy to use the wrong socket or turn the wrong knob.

BTW, bad cables is something I do manage to avoid most of the time as I make most of my own and I have lots of them - I owned three hundred metres of mike cable before I owned any proper mikes ...