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Ground noise

 
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Aspetos



Joined: 03 Oct 2011
Posts: 4

PostPosted: Sat Sep 22, 2012 7:15 pm    Post subject: Ground noise Reply with quote

Hello everybody!
Has anyone had any problems with ground loop noise or anything similar?
On my wavedrum I hear a constant buzz/hum when not touching the rim and it goes away when i do; like what happens with electric guitars when you touch the strings.
It's not loud but it gets REALLY annoying when heard through a PA system...
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MidiSaron



Joined: 01 Aug 2012
Posts: 21
Location: Dortmund, Germany

PostPosted: Tue Sep 25, 2012 3:38 pm    Post subject: Reply with quote

Aspetos wrote:
Has anyone had any problems with ground loop noise or anything similar?
On my wavedrum I hear a constant buzz/hum when not touching the rim and it goes away when i do; like what happens with electric guitars when you touch the strings.
It's not loud but it gets REALLY annoying when heard through a PA system...


A bad cable from Wavedrum to PA perhaps? Did you try different cables? A DI box might help also.

Is the noise level independent from the setting of the volume knob of the Wavedrum?

Did you set your Wavedrum to x2 output level? If not, the Wavedrum's output is very weak so you have to set the gain on your PA quite high, which makes it more sensitive to noise.
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Aspetos



Joined: 03 Oct 2011
Posts: 4

PostPosted: Tue Sep 25, 2012 11:53 pm    Post subject: Reply with quote

No,no,I'm talking headphones here..
Standard output level.
And I hear a constant humming sound -like the sound you get from an electric guitar that needs a set-up,you know- that goes away when I touch the rim.That's why I thought that it may be a grounding issue.Maybe something with the AC adaptor...
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MidiSaron



Joined: 01 Aug 2012
Posts: 21
Location: Dortmund, Germany

PostPosted: Wed Sep 26, 2012 7:05 pm    Post subject: Reply with quote

Aspetos wrote:
No,no,I'm talking headphones here..


So there's noise/hum even if the wavedrum is only connected to your headphones and the power supply and nothing else?
Just checked with my Wavedrum (which is noise-free), the rim is connected to signal ground. Maybe that connection is broken in your Wavedrum? You could check by connecting signal ground (e.g. from a metal phone plug in an output jack) to the rim. The rim itself is coated with a thin layer of oxide, but the tension bolts should give a good electrical contact to the rim. Just connect a tension bolt to the outer part of a plug of a cable plugged into the wavedrum. If the noise goes away this way then the internal ground connection to the rim is broken.
Alternatively, you could check the ground connection of the rim with am ohmmeter.

Does the noise level change with the setting of the volume knob and/or the rim Algo or PCM level settings?
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Aspetos



Joined: 03 Oct 2011
Posts: 4

PostPosted: Wed Sep 26, 2012 10:11 pm    Post subject: Reply with quote

Yes,that's right,only headphones and adaptor connected..
The noise is constant no matter the volume/rim Algo/PCM level settings.

Could you elaborate on that connecting-signal-ground-from-phone-plug idea?

How can you tell that yours is connected correctly?
(appart from not making a noise I mean!! Laughing )
I can only tell that the connections of the sensor don't seem broken,there is no GND indication..
Thanks very much for the trouble by the way!
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MidiSaron



Joined: 01 Aug 2012
Posts: 21
Location: Dortmund, Germany

PostPosted: Thu Sep 27, 2012 5:27 pm    Post subject: Reply with quote

Aspetos wrote:
Could you elaborate on that connecting-signal-ground-from-phone-plug idea?


My idea was, plug a guitar-type cable into the Wavedrum's output, and, while monitoring the noise with headphones, try to make contact between the metal housing of the plug at the other end of the cable and one of the tension bolts. If possible don't touch neither thr rim (the noise then goes away anyway as you wrote) nor the plug. If anything changes then there's no good connection between ground and the rim.

Here's a much easier way: just plug in the cable and touch the plug at the other end. If the effect is the same as when touching the rim, then the ground connection is probably good.

Aspetos wrote:
How can you tell that yours is connected correctly?
(appart from not making a noise I mean!!


I measured the resistance between the rim and ground at the output with an ohmmeter. It's less than 1 ohm.
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Aspetos



Joined: 03 Oct 2011
Posts: 4

PostPosted: Fri Sep 28, 2012 12:43 pm    Post subject: Reply with quote

OK,I tried the cable test and check this out:
with one pair of headphones (typical,mp3-player-style,in-ear headphones) the noise is present and touching the jack of the cable at the other end makes it stop;which tells us that there is a problem with the ground connection of the rim,right?
But with another pair of headphones (closed-type studio headphones but the cheap kind!) the noise disappears..!
Both headphones are plugged in the wavedrum's mini-jack socket,no adaptors used.
So,what is going on??
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MidiSaron



Joined: 01 Aug 2012
Posts: 21
Location: Dortmund, Germany

PostPosted: Fri Sep 28, 2012 5:59 pm    Post subject: Reply with quote

Very mysterious.
I got curious and just removed the two screws that held the tiny circuit board next to one of the rim piezos (the wavedrum was taken apart for a different reason anyways), thus disconnecting the rim from ground.

Now there's indeed hum, but the other way round: the hum gets louder when I touch the rim. Also, it depends on the setting of the volume knob, and it sounds very different for different patches. For instance, with the conga patch 19 there's no hum at all. But when I touch the rim I get a nice and even conga roll Smile Obviously the rim sounds get triggered by the 50 Hz hum.

So on your Wavedrum it must be something else that is faulty, but I have no idea what this could be. BTW I tried various headphones too, but there was no difference.
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