UMIK-1 - w/ USB filtering and/or external 5V ? - diyAudio
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Old 25th November 2016, 08:23 AM   #1
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Default UMIK-1 - w/ USB filtering and/or external 5V ?


Most of us know that the USB interface can and usually causes rather severe issues on an attached audio interface.
Most of us experienced this with DACs.
IMO there got to be issues expected on ADCs as well.

It takes extreme efforts to be able to cope with these USB issues. And still there's no end in sight in the industry. Every other month a new USB filter gadget gets released.

Now my Qs related to UMIK-1.

1. I'm wondering if anybody tried a USB filter like iPurifier or AQ Jitterbug
2. I'm wondering if anybody tried injecting clean 5V instead of the polluted PC-USB-5V

Care to share your experience?

Let's assume there'd be a difference. I pretty much expect it.
Then this in turn might make the original calibration rather useless!

What's your opinion/?

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Old 26th November 2016, 01:28 AM   #2
seanp2k is offline seanp2k  United States
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I haven't tried the Jitterbug but I have an ADUM4160-based USB isolator from eBay. It definitely eliminates the ground loop for my electronics testing bench. There's zero audible difference when running it with an ODAC or HiFiMeDIY Sabre 9018 or Behringer UAC202 driving a DEQ2496 over optical. I tried with a few headphones including Shure 1540s and LCD-XCs driven by a Rupert Neve RNHP.

The ADUM chip definitely provides electrical isolation, but it doesn't solve any problems which didn't exist in the first place for my setups. If you have problems with USB noise I would definitely try it. HiFiMeDIY also makes an isolator based on the same Analog Devices ADUM4160 which I would trust. I would be much more suspicious of devices like the Jitterbug. Reviews of the JB range from ~magical improvements to no discernible difference. IIRC the JB is just some resistors inside. I can try throwing my setup with and without the isolator on my scope to see if there's any difference in distortion. It's just a basic Rigol 1054z. I'll report back if I end up testing it out.

I've also tested a OneAC isolation transformer for mains with my UCA ->DEQ->RNHP setup. It didn't make anything sound worse, but also didn't improve anything. I can't tell the difference between the Sabre 9018 and the DEQ2496 when they're level-matched (the RNHP has buttons to switch between XLR, RCA, and 1/8" so it's easy to AB test). I can say that I very slightly prefer either over the ODAC, but the difference is very very subtle. IIRC I paid $30 for the oneac on eBay.

My bench equipment is all plugged into a Tripp Lite IBAR12 which is also supposed to provide some filtering. I've never noticed a difference. I just wanted some nice industrial power strips with surge protection. I got a few for $50 each from eBay. The other is plugged into my icepower amp powering some parts express kit speakers. It sounds the same with or without it.
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Old 5th December 2016, 07:16 PM   #3
Davey is offline Davey  United States
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In my case, I see no difference in the noise floor of the UMIK setup whether it's powered from my laptop or powered via a nice external USB 5-volt supply.

Regardless, I don't see why any of this would render the calibration useless. When using the microphone during acquisition there would be signal present and you should be well above the noise floor of the microphone/ADC combination.

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