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Author Topic: console noise  (Read 1810 times)

Jeremy-PR

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console noise
« on: May 26, 2004, 12:23:52 AM »

Good evening
I am working on a noise problem with an Amek M2500 console and was looking for some advice. Here is the scenario:

The 2 Mix buss has a buzzing, static, dirty sound you can hear at normal listening levels. It is consistant no matter whether the channels are muted or not.

First thing I did after disconnecting everything to see if it was the console or not,  I replaced all the IC's on the master module. No change, so I pulled all 48 input channels and the console is dead quiet. So I started replacing channels to see if one of the channels is causeing the noise. the first 24 or so that I put back didn't bring back the noise, but it began creeping back in cumulatively with the last 18 or so.

My question is, what is the most likely cause and where should I go from here?

Thanks,
Jeremy
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John Klett

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Re: console noise
« Reply #1 on: May 26, 2004, 09:10:37 AM »

power supply probably - does this noise come out of other busses and outputs or just the 2mix?
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ssltech

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Re: console noise
« Reply #2 on: May 26, 2004, 10:12:16 AM »

If it's a true 120Hz hum, then PSU is a good thing to look at, but it's rather more likely to be the internal buss amplifiers, which increase gain as they are terminated with more and more modules.

Scope the rails loaded and unloaded. If you see no difference, look to a better internal greounding scheme, something like the 200B mod that Eddie Ciletti details on his site. many Ameks of the era had similar problems.

I should add that when you go noise testing to test the guts of a console, the only things that should be connected are the console and the monitors. Everything else should be disconnected. If the buzz isn't there under those circumstances, your installation should be investigated, with special attention paid to the grounding philosophy.

Good luck,

Keith
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MDM (maxdimario) wrote on Fri, 16 November 2007 21:36

I have the feeling that I have more experience in my little finger than you do in your whole body about audio electronics..

Jeremy-PR

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Re: console noise
« Reply #3 on: May 27, 2004, 12:44:17 PM »

Thanks for all the great ideas... I will attach a scope and let you know what I find out...

the noise is only present on the 2 mix output. It is dead quiet when listening to the tape in's.  the noise is also the same whether or not the rest of the room is plugged into the console.

Thanks,
Jeremy
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eddieaudio

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Re: console noise
« Reply #4 on: June 16, 2004, 09:57:25 PM »

Hey Keith,

thanks for the plug!

If the noise builds up when modules are assigned to a buss, like the 2-mix, then it is likely to be a grounding issue.

ec
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Erik

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Re: console noise
« Reply #5 on: June 18, 2004, 02:37:00 AM »

eddieaudio wrote on Wed, 16 June 2004 21:57

If the noise builds up when modules are assigned to a buss, like the 2-mix, then it is likely to be a grounding issue.


Well, all that means is that some noise is getting into each channel individually and it's building up gradually.

Since there's a threshold of channels after which this happens -- and since it didn't happen previously -- I'm guessing that the supply needs to be rebuilt.

It doesn't cost much, it's an easy variable to eliminate, and the money spent almost always gives a concrete benefit even if it's not the cause of the problem.

--Erik
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Erik Gavriluk, Bomb Factory Recording Studios
"The modern trouble is not the use of machinery, but the abuse of it." --Gustav Stickley, 1909
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