Hello Joe!
In a message to Donald Quarles  Joe Beels wrote:
JB> *** Quoting Donald Quarles to T Owen dated 03-23-96 ***
>> 
>> DQ>> I have a mackie mixing board 16 channel being run in stereo and
>> DQ>> also a stereo graphic E.Q. and a processer and Bose in the
>> DQ>> ceiling speakers and a 1000 watt per channel power amp and also
>> DQ>> for the motiores i use a pevey head 300 watts per channel. what
>> DQ>> the problem is when i turn the thing up i get a low freg. hum and
>> DQ>> can not fiqure it out when no one is using the system is hum
>> DQ>> likes a boat motor off in a distance..
>> 
>> TO> Sounds like a ground loop to me. Is everything plugged into 
>> TO> the same leg of AC power? Are you running long unbalanced 
>> TO> lines? Are signal cables (esp. unbalanced) running paralell 
>> TO> to AC feeds? Tell me how things are wired up, and I may have 
>> TO> some ideas. Take care. 
>> 
>> well thank you first for replying to me. This is in our church
>> we have had this hum since i have been there we havbe a 100'
>> snake runnign from the back of the building to the stage on the
>> stage we have 16 plugs all sheilded and grounded the snake is ran
>> through the ceiling in a plasitic pipe. then as they come to the
>> back they go into the sound room and hook up to the XLR plugs on
>> the mackie now for the monitors we have a cable coax running
>> about 65 foot coming from the stage which has two peveay's
>> montiors and then through the 65 foot line and into the peavey
>> montior head. and in the sound romm we have a E.Q, Power bass
>> amp. and effects machine for speakers they have insatlled the
>> bose with the sub woofer system.. that is it in the nut shell and
>> kind of help would be apperacited.
>> 
>> Donald Quarles A.K.A BAD
JB> I do a lot of live stuff with portable systems (several 
JB> times a week).  What I do to eliminate this problem is:
JB> a. Power my console and effects/processing rack from the 
JB> exact same power source as my power amplifiers... in my case 
JB> this involves running a 100' 12/3 SO cord to the power amp 
JB> rack from the console. 
JB> b. Require the use of an active direct box with ground lifts 
JB> for keyboards, bass etc. direct inputs (no cheap 
JB> transformers), to eliminate ground loops from different 
JB> circuits that power those items. Rule of thumb is that if it 
JB> plugs into the snake, it either has a ground lift/isolation 
JB> or it's on the exact same power source ... 
JB> This usually does it for me .... however .... sometimes
JB> neither of those things eliminate the problem ... I
JB> generally turn everything up a little and start un-pluging
JB> stuff from the snake one by one till the problem disappears.
JB> If I'm standing there with nothing plugged into the snake,
JB> then I starts looking ....
well thank you very much took your advice and after everything is
unpluged it is still doing it. I think maybe something to do in
the moniters.
Donald Quarles A.K.A BAD
... Boot & ye shall see. Replace & all will be made clear.
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