[sdiy] slightly OT - earth hum

[Chromatest J. Pantsmaker]

How do you hear the hum from the tapco, when it's just the tapco?  Is
it headphones?  What is your connection to the amplifier/speakers?  If
the tapco is plugged into the proper power cord/wallwart, and you have
NOTHING else (inputs or outputs) connected, and are monitoring the hum
with headphones, I'd get a new mixer.

On 3/24/11, Dave Kendall <davekendall at ntlworld.com> wrote:
> Thanks all.
>
> The nord problem *was* something dumb and obvious - the Nord has
> unbalanced outputs, and I was using balanced leads.. Doh! (slap
> forehead)
>
> Harry - so I guess it may be an advantage that the gear is only ground
> connected via audio lead grounds?
>
> It's being used as a live keyboard + Mic mixer.
>
> cheers,
> Dave
>
>
>
> On Mar 24, 2011, at 14:37, Harry Bissell wrote:
>
>> BTW in my system I try to make the audio grounds (via shields) the ONLY
>> connection by isolating all rack devices from the metal racks (and
>> each other),
>> making sure that no MIDI cables have a ground connection (they should
>> not anyway...)
>> and isolating all three-wire grounds from the mains. (I'm in the USA
>> btw.. 120VAC)
>>
>> If a rip-roaring circuit fault trashes my audio cables and selected
>> pieces of gear,
>> so be it. At least when the system is working there is a substantially
>> lower noise floor.
>> Isn't that what studio gear is supposed to deliver anyway ?
>>
>> H^) harry
>>
>>
>>
>>
>> ----- Original Message -----
>> From: Dave Kendall <davekendall at ntlworld.com>
>> To: sdiy DIY <synth-diy at dropmix.xs4all.nl>
>> Sent: Thu, 24 Mar 2011 10:29:25 -0400 (EDT)
>> Subject: Re: [sdiy] slightly OT - earth hum
>>
>> Hi. All machines are on the same mains circuit.
>> Both Nord and mixer are not grounded by their cases. Would the easiest
>> way be to fit a 3-pin mains plug to the Nord (with earth connection)
>> and the mixer if possible?
>>
>> I guess the real question i, whereabouts in the nord and tapco to
>> attach the ground points...... I suppose it would be easy enough to
>> connect a mains earth to the audio GND, but interestingly, without the
>> MIDI cable between K2661 and nord it hums, suggesting that the Nord's
>> audio GND is maybe not connected to the chassis, but the metal barrel
>> of the MIDI jack does connect?
>>
>> I'm missing something obvious I'm sure..
>>
>> cheers,
>> Dave
>> On Mar 24, 2011, at 14:14, Ben Lincoln wrote:
>>
>>> Dave, you've probably already looked into this, but are all of your
>>> devices on the same mains circuit? Nearly all of the ground noise
>>> issues I've run across over the years were the result of connecting
>>> things that were powered by different circuits.
>>>
>>> It sounds like that's not what's going on with the mixer itself, if it
>>> hums with literally nothing else connected to it, but maybe it's
>>> what's happening with the Nord + mixer combination? Is the mixer
>>> physically grounded/earthed by some other means, e.g. it has a metal
>>> case and is sitting on a metal cabinet that's sitting on a concrete
>>> floor, or something like that?
>>>
>>> On 2011-03-24 07:02, Dave Kendall wrote:
>>>> Hi.
>>>>
>>>> I may have to modify a mixer or keyboard, so it's not that OT... I
>>>> have a nasty hum/noise problem, and maybe someone here has hit this
>>>> problem before....
>>>> A Tapco 6306 mixer is connected to a Yamaha O3/D. The tapco hums
>>>> loudly (60Hz with harmonics) with no audio connections made. It stops
>>>> humming when balanced audio jacks from a Kurzweil K2661 are connected
>>>> to it.
>>>>
>>>>  The K2661 has a 3-pin mains input, the Tapco is a wallwart (9V AC)
>>>> As soon as a Nord electro (2-pin mains) is connected to the Tapco,
>>>> There is a horrible digital noise from the Nord, modulating in a
>>>> pattern at a few kHz or so I guess.
>>>> However when Midi out of the K2661 is connected to the nord's MIDI
>>>> in, all the problems go away.
>>>>
>>>> Would it be worth Modding both the tapco and the nord to accept 3-pin
>>>> mains somehow?
>>>>
>>>> Anyone done this sort of thing before? Any advice would be most
>>>> welcome.
>>>>
>>>> Apologies if this is too off-topic....
>>>>
>>>> cheers,
>>>> Dave
>>>>
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>>
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>> --
>> Harry Bissell & Nora Abdullah 4eva
>>
>
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-- 
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-Chromatest J. Pantsmaker
http://www.chromatest.net