humming on digital 8 track

L

loungepenguin

New member
Hi

I very recently bought a Zoom MRS802cd. I am having some humming noise problems with it.

Basically I plug my electric guitar in (with a brand new decent £25 thick guitar cable), turn the input and recording levels up to the required point and there is a humming sound. This is cut down to almost nothing if I put my fingers across the strings.

I have also plugged my acoustic in. This has a home made bug built into it so I was not expecting it to sound amazing but the hum is really bad. This time though if I put my fingers over the input on the guitar the hum disappears.

If the cable is just in the machine’s input and not plugged into anything else there is a nasty buzz unless I touch the end of it.

I have tried turning off all other electrical equipment in my room but no better. I have trioed moving away from the machine but still no good. The manual says I might need to ground the recorder. There is a little screw under the machine at the back and it says to use this to ground but does not mention how.

I had a little search on how to do this but nothing that I saw seemed to explain simply to a newbie how this is done.

Any help would be very appreciated!

Thanks
 
That humming is not a problem with the Zoom, but it's a ground issue - possibly on the wiring of your guitar -- but ALL guitars hum and buzz a little, especially with high gain... it's the nature of the beast. (It's also another benefit to mic'ing an amp - no chance of a ground loop between the instrument and the recorder!)
 
It could - IF the problem is a ground loop between the recorder and the guitar -- if it's a wiring issue on the instrument itself, it won't help.....

Humming from grounding problems can be tricky to diagnose and fix......
 
I don't understand how you could have a ground loop involving an instrument that is not grounded. It sounds to me like the instruments are picking up some stray EMF. loungepenguin, do you by any chance live under or near high-tension power lines?
 
DonF said:
I don't understand how you could have a ground loop involving an instrument that is not grounded.
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The hum stops when he touches the strings -- which means the circuit is finding a ground through HIM -- that's a ground loop........
 
I've heard of ground loops causing hum, but I've never heard of a ground loop stopping hum. I guess there's a first time for everything.
 
No big power cables near me. I could try getting what has been suggested but I would like to try it first.

Someone else also recommended some kind of wristband that gets attached to the bridge of the guitar. Not sure about that though.

Any help on this is much appreciated

Thanks
 
DonF said:
I've heard of ground loops causing hum, but I've never heard of a ground loop stopping hum. I guess there's a first time for everything.
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A ground loop occurs if a signal can find its way to ground through multiple points. Some of those points may not be the best path to take (such as the singer getting a shock from a mic on stage).... same with the guitar. Something in his signal path is not grounded properly... and when he touches the strings, he's giving the signal a ground to go through - unfortunately, it's through HIM. When there's no anomaly in the circuit, he won't notice anything, but if something goes wrong and he happens to be the ground path - that can be a dangerous situation......

I don't know where you got the idea I said a ground loop "stops hum"... the term "ground loop" simply defines the fault condition that occurs with an electrical signal having multiple points to ground to - and one of its symptoms is a hum being heard through the audio signal of the affected circuit. What stops the hum is correcting the circuit fault (and finding that fault is what is sometimes difficult to locate and/or diagnose!)
 
Blue Bear is the man.
I agree, it sounds like a grounding issue. In my last band's practice space, the whole unit was ungrounded so we had to play on carpet, otherwise you'd get a nasty lingering current on the concrete. It was incentive to get the set done quickly, but there were some awful shocks back in the day.
This had almost nothing to do with anything.
 
*DonF shakes head*

A ground loop is an electrical fault wherein an audio circuit (any circuit, really, but it's audio we're concerned with here) contains more than one distinct path to ground. If the paths to ground have different impedances (which they almost certainly will), current will flow at the mains frequency, which is audible as hum. So we agree on the definition of "ground loop".

Blue Bear, you said, "The hum stops when he touches the strings -- which means the circuit is finding a ground through HIM -- that's a ground loop." The only way I can read this is, "he touched the strings, creating a ground loop, which stopped the hum." I'm always looking to learn something new, so I pointed out the seeming inconsistency, knowing that you would set me straight. Thank you for not disappointing.

I think what's going on is that loungepenguin's body is seen by the circuit as a "pseudo-ground" in the sense that it is acting as a source of electrons. (If he's barefoot on a concrete floor, which he didn't state, my opinion would be different.) The fact that there's hum even with an unconnected guitar cord makes me very confident that what we have here is a stray EMF problem rather than a ground loop.

Providing a true ground in this situation might be just the ticket. Connect the grounding screw on the zoom to a good ground, like the center screw on an electrical outlet cover plate. If you're not confident of the wiring in your building, proceed with caution. Especially if you're barefoot on a concrete floor! :D
 
DonF said:
*DonF shakes head*

A ground loop is an electrical fault wherein an audio circuit (any circuit, really, but it's audio we're concerned with here) contains more than one distinct path to ground. If the paths to ground have different impedances (which they almost certainly will), current will flow at the mains frequency, which is audible as hum. So we agree on the definition of "ground loop".
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Yup! ;)


DonF said:
Blue Bear, you said, "The hum stops when he touches the strings -- which means the circuit is finding a ground through HIM -- that's a ground loop." The only way I can read this is, "he touched the strings, creating a ground loop, which stopped the hum." I'm always looking to learn something new, so I pointed out the seeming inconsistency, knowing that you would set me straight. Thank you for not disappointing.
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The way I meant that statement was "The hum stops when he touches the strings -- which means the circuit is finding a ground through HIM -- that probably means he has a ground loop somewhere."

You misinterpreted what I meant by that last part of the statement! Glad we cleared this up!! :p
 
wow - thanks for all the help! good to get a discussion going!

It's definitely getting some kind of grounding thing going through me. The cable buzzes when it's not plugged in unless touched an on my acoustic the hum stops if I touch the input. (the bug inside is just connected to wood and not the strings). My Electric is a pretty decent £300 Tele and I have never had problems with it. Strangely a Mic plugged does not cause as much as a buzz.

I tried to ground the unit but I can't seem to find anything to ground it to. If I attach a wire to the screw and touch the other end it makes no difference. I am 2 floors up standing on carpet, and the zoom is on a wooden shelf.

THe unit that I mentioned has a "ground lift" - does anyone know what this is? Do you think it might help? I might just get it anyway as I am sure that it will get rid of a bit of the buzz anyway. I just need to get an XLR cable for it.

Any help very appreciated!

Thanks
 
What fun! Spent hours last night trying to get to the root of this with no joy.

I moved the zoom downstairs, out of my room and plugged it into one socket with nothing else. No other electrical equipment near it.
I bought a Behringer DI100 Active Direct Box and an XLR to XLR cable. As far as I could tell this did nothing. I pressed the ground lift button and still nothing. I pressed one of the Switchable input attenuation which allows input levels of up to +50 dBu – this seemed to work except the guitar went really quiet so I had to turn the volume up again and back came the buzz.

One weird thing though was that if I put my hand on the DI box the buzz lessened but not as much as if I put my hand over the strings.

I then got a friend to come around and tried it with a different guitar lead – same problem.
We then tried it with his guitar which is really expensive and there was less of a buzz and the guitar sounded a little louder but the buzz was still there and again when you put you fingers over the strings it pretty much went.

We then tried grounding the Zoom using a wire and the screw at the back of the unit. The manual is not very helpful in this but we connected the wire to the zoom and then tried putting the other end on radiators, walls, the floor and finally us – this all made no difference the only slight difference was if you pinched the other end of the wire with your fingers continuously you could hear a slight clicking sound but nothing else. You could remove the hum by connecting the same wire to the bridge of the guitar and pinching the other end.

One suggestion I have had is to use something electricians use to (I assume) stop static – connect a wire to the bridge and the other end to a wristband around my wrist. I have a feeling this would work but it seems a bit weird to have to do this and almost dangerous! Pretty rock and roll way to go I suppose though!

Basically the electric is useable as I touch the strings almost all the time but if you are only touching one string the buzz is louder than if you are touching all of them so it’s still there. If I use my acoustic the buzz is always louder than the sound (I know my acoustic bug is never going to be brilliant) unless you touch the input where by the buzz almost disappears.

This leaves me thinking – is the Zoom not working properly or is this because (in past experience) Zooms are always not brilliant and this is just the way things are?

Any help on the desperately appreciated!
 
oh yer forgot to mention something else - with the guitar cable plugged into the zoom and not my guitar there is a buzz but if I move the end of the cable that would be plugged in my guitar within one inch of the unit the buzz goes! strange!
 
loungepenguin said:
...We then tried grounding the Zoom using a wire and the screw at the back of the unit. ... [W]e connected the wire to the zoom and then tried putting the other end on radiators, walls, the floor and finally us....
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Did you try a cold water pipe? They usually make a good grounding point.

Thanks for the update. Stick with it!

Don
 
I tried the radiator, but in my room at least there is nothing else. I am going to try one of the wrist bands later.

Also, I emailed the people I bought it off and they said that it is unlikely that it is the Zoom and to try it in someone elses house. Going to try this later but if it works in someone elses house and not mine then that is not good. Maybe I'll have to buy a new house to go with it!

much appreciated
 
loungepenguin said:
I tried the radiator...
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Yes, I understand. Just wanted to make sure you understand that a cold water pipe is special in that it generally has a much more direct connection to the earth than any hot water pipe or radiator.

Have you ever had this problem with any other piece of equipment, like a guitar amp? Or does everything else work fine?
 
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