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Buzz from Mic and guitar through DI box


aluk

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We have an acoustic guitar (with internal) preamp and also a Shure Green Bullet mic. The guitar goes into an input on a MOTU interface, and the mic goes into a Behringer ADA8200 which is connected to the MOTU via ADAT. Both mic and guitar are unbalanced with around 5m/15ft of cable each terminating in 1/4" jacks. Phantom power is enabled on the ADA8200 but won't be going through the TRS jacks.

 

This all works fine, with no hum or buzz.

 

I wanted to tidy up the cabling, so we have a 10m/30ft 8in4out XLR snake on a reel.

 

We connected the green bullet and guitar plugs into the 2 inputs on an ART DTI (http://artproaudio.com/isolators/product/dti/) and then the XLR outputs on the DTI box to 2 channels on the snake which then went into the same channels as before on the MOTU and ADA8200, but now using the XLR inputs.

 

Both the Green Bullet mic and guitar had a continuous low level buzz on their channels when using the snake. It was as if the snake was not balanced and was picking up mains interference.

 

We also had a Bass (XLR out from a Helix), main vocal mic, and a powered monitor also coming directly through the snake (not through DI boxes) and they worked fine. They are all balanced connections.

 

Any ideas on why I was getting buzzing through the ART DTI box? There would have been (unneeded) phantom power on one of the channels but not on the other.

 

Thanks!

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Not sure if that DI you are using is stereo. Need to try a stereo DI like the Radial Pro D2 and keep the signals separate.
Montage 7, Mojo 61, PC-3, XK-3c Pro, Kronos 88, Hammond SK-1, Motif XF- 7, Hammond SK-2, Roland FR-1, FR-18, Hammond B3 - Blond, Hammond BV -Cherry
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I've simplified for testing with 1 channel, no phantom power, and no snake.

 

SM58 --> ADA8200 using 1 x XLR to XLR balanced cable - NO HUM

SM58 --> ART DTI --> ADA8200 using 2 x XLR to XLR balanced cables - HUM - Why?

 

Do I just need a better DI? Should I get an active one or passive?

 

 

 

 

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Update - I picked up a Radial Pro D2.

 

That has fixed the problem, and there is no hum when plugging the SM58 in. I am not sure why though. What is the difference electrically between the ART and the Radial?

 

I don't think the ART is broken. I also have a Behringer Hum Destroyer, which behaved the same as the ART, and did not remove the hum.

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One is cheap. The other is quality.

 

I took a closer look at the ART. I figured it was probably a cheap powered circuit, but it uses transformers to isolate the signal like the Radial. It SHOULD work. Maybe the phantom power screwed it up, or maybe the absence of a ground lift switch made it fail to work.

Moe

---

"I keep wanting to like it's sound, but every demo seems to demonstrate that it has the earth-shaking punch and peerless sonics of the Roland Gaia. " - Tusker

http://www.hotrodmotm.com

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