Crackly 48v from Apogee Duet

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Level 1

8 points

Crackly 48v from Apogee Duet

Anybody else having this problem? I have a MacBook Pro, running Logic Pro 8 on Leopard, and recently got the Apogee Duet. It sounds amazing, aside from a consistently crackly signal whenever I send 48v to my AKG C 451 B condenser mic. When I use a mic pre to supply the phantom power (in my case a UA Solo/610) there's no noise. It seems to only happen to the 451, though -- my Neumann U87 is unaffected when it gets the 48v from the Duet. Thoughts? Similar issues?

macbook pro, Mac OS X (10.5.1)

Posted on Dec 16, 2007 2:32 PM

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Answer 1

Dec 16, 2007 2:49 PM in response to cphm

Phantom power output is highly variable - from as low as 9V up to 48V and mics vary in what they need. Maybe the power from your Duet is just enough for your Neumann, but your 451 needs a higher voltage than your Duet's output is giving it and is right on the cusp. The fact that using the 610 is clean, but the Duet isn't, might indicate that this is the case.

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Answer 2

Dec 16, 2007 2:55 PM in response to John Alcock

One more thought - in my Neumann docs is says that the current required is between 2-4 mA, but I do know that other mics need much more - maybe your 451 is one of them - see if it's mentioned in the docs.

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Answer 3

cphm Author

Level 1

8 points

Dec 16, 2007 3:13 PM in response to John Alcock

thanks for the input. . .

Checked the docs on the 451, says it takes 9-52v, the 'current consumption' being <2 mA. Would it be possible that it's getting sent too much power?

(I'm fairly electrically-illiterate)

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Answer 4

Dec 16, 2007 3:36 PM in response to cphm

No - it draws what it needs. Is this crackling on either Duet inputs? Are you using different mic cables?

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Answer 5

Dec 16, 2007 4:59 PM in response to cphm

hi,
no problems with any neumann here.
that's km88, km53, u47, tlm170.
all other brands work with duet, no sweat (rhyming intended)
is your buffer set too low?
also have rosetta 200, and all(mics) work and sound identical to duet.
no difference in headroom at all.
DR9.

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Answer 6

Dec 16, 2007 6:39 PM in response to cphm

I'm on a macbook but no problems with phantom power here.

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Answer 7

cphm Author

Level 1

8 points

Dec 16, 2007 7:30 PM in response to John Alcock

Both inputs create the same crackling and only with the 451. I've tried all the cables -- i can actually plug the 451 directly into the breakout cable -- and it still makes the crackling. It's likely not the mic, either, because I have two 451s and they both have the same problem. Incidentally, I could faintly hear the digital crackling on the 451s on my old Mbox using ProTools, it just wasn't nearly as loud.

Might be a hopeless case. Is it possible to adjust the 48v output on the Duet? Buffer size makes no difference.

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Answer 8

Dec 16, 2007 8:27 PM in response to cphm

cphm wrote:
Might be a hopeless case. Is it possible to adjust the 48v output on the Duet? Buffer size makes no difference.

I shouldn't think so. It's possible that you just have an interface that is putting out an especially low output - you could measure it, of course, but as you're not a tech you probably don't have a suitable voltmeter lying around. I'd talk to Apogee - I've had excellent support on other equipment and they may swap it out. Or talk to AKG - maybe the 451 is fussier about voltage. Neumanns are very forgiving; maybe 451s are less so.

Good luck - I'd be interested in hearing what you find out.

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