Go Between Humm

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nikonet
Posts: 6
Joined: Fri Jul 30, 2010 9:34 pm

Go Between Humm

Post by nikonet »

Hi, i plug a Go between card on my 1290EZ préamp: between the input transformer and the input XLR plug.
All is ok with Pad and phase reverse switch. Préamp works properly.

But when i switch on phatom power: I ve got humm: 350hz, 715hz and 1000hz. Condenser mic works but there's some humm.
So i check the power:
-48v between 0v / 48v
-40v between in+ / 0v
-40v between in- / 0v
-40v between out+ /0v
-40v between out- /0v
-0v between in+ / in-
-0v between Out+ /Out-

Any idea of my mistake?

I forget: i use switched power supply with +V, -V, ground: i pluged +v to 48v input; -v to 0v input; the ground connected to the xlr input.

Thanks for all your job !!!

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Joe Malone
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Posts: 2070
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
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Re: Go Between Humm

Post by Joe Malone »

nikonet wrote:Hi, i plug a Go between card on my 1290EZ préamp: between the input transformer and the input XLR plug.
All is ok with Pad and phase reverse switch. Préamp works properly.

But when i switch on phatom power: I ve got humm: 350hz, 715hz and 1000hz. Condenser mic works but there's some humm.
So i check the power:
-48v between 0v / 48v
-40v between in+ / 0v
-40v between in- / 0v
-40v between out+ /0v
-40v between out- /0v
-0v between in+ / in-
-0v between Out+ /Out-

Any idea of my mistake?

I forget: i use switched power supply with +V, -V, ground: i pluged +v to 48v input; -v to 0v input; the ground connected to the xlr input.

Thanks for all your job !!!
The GO between cannot make any hum so you need to check all 0v and XLR in and out pin 1s are connected to the 0v of the +24v supply and the 0v of the +48v supply. They should be 0ohms between all these points to each other.

Also check that the XLR in and out are wired mirror images of each other. As we see to many times people wire them the same which reverse pin 1 and pin 3 on one XLR.

Most SMPS power supplies do not like having no real load on them and can make noise but not usually hum.

What 48v power supply are you using ?

Try turning on phantom power with a dynamic SM57 or SM58 to see if you still get hum with phantom on?

Otherwise some clear well lit photo's for me to check over always helps.
Joe :-)
JLM Audio
Capturing Audio without Injury

nikonet
Posts: 6
Joined: Fri Jul 30, 2010 9:34 pm

Re: Go Between Humm

Post by nikonet »

Thanks for the answer.

I checked xlr pin: all is ok except Pin 1 at the preamp xlr out connected to ground. I removed it.

So i tested again with condenser mic: always big noise. I changed mic: no noise....!!!!! I think i made a big mistake few days ago that break my condenser mic....sniff. I will open it to see what hapen

So all is ok with go between !

for information, my power supply:
24V: Mean Well RS-75-24
48V: Mean Well RS-50-48

Thanks for all your great job. And nearly SUMO !!!! I can't wait !!!

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