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Focusrite ISA 430 Noise

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Focusrite ISA 430 Noise

Postby jodaki » Fri Sep 18, 2020 10:50 am

Hi,

I have a 430 MKII which is making a disturbing hum when the clock cable (coax) is attached to its master (no hum if the master end is unplugged), very noticeable at preamp levels over 30db.

Nb. this is regardless of whether a mic is attached or not.

The setup is:

430 MKII into a ISA 428 MKII into an Orion 32+ gen 3

Im using the antelope as the master clock.

The 430 hums in all variations of its 'Ext Sync' button (whether off or word clock locked) but is silent when the '256x' setting is active (I dont know what 256x is).

The coax Im using is very short and is a good quality lead.

The buzz persists if I take the clock signal from the antelope (using a different lead) rather than the 428.

I hear no hum on the 428 even at max preamp levels.

The 430 is connected to the Orion via SPDIF. Is there some other way I can set this up? Or can anyone think of a cause or fix?

thanks, John
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Re: Focusrite ISA 430 Noise

Postby Hugh Robjohns » Fri Sep 18, 2020 11:41 am

The cause is most probably a ground-loop via the BNC screen, so I'd look at the grounding arrangements of that whole signal chain and other things that might be connected.
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