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Old May 5th, 2008, 04:03 AM   #1
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question to all 302 users

plug your headphones into the mixer and do this quick test: choose one channel and raise the gain and fader all the way up. on channel 2 and 3 i only notice some kind of noise getting louder, i don't even know if it comes from the hadphone amp or what. i don't find it disturbing anyway. on channel one i hear a totally different one, sounding more like an electric interference. very disappointing..
i called the dealer who sold me the 302 here in italy. i was beginning to explain him the problem when he went: "oh it's about channel one.. it is normal, they all do like that". this seems strange to me but i feel like i have to believe him somehow since he knew what i was going to tell him..
true is that i never have to raise the levels so high on any channel so the problem might turn out to be a non issue, still i don't feel comfortable with such a limitation.
please 302 users out there let me know how your sd mixer behaves on channel 1 with pots all open..
thanks

pietro
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Old May 5th, 2008, 08:38 AM   #2
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Dear Pietro,

Are you running this test with nothing connected to the inputs?
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Old May 5th, 2008, 09:43 AM   #3
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nothing connected. i noticed that the problem disappears when settins the imput to line, i don't remember about the phantom.
i'll run the test again tonight with a cable plugged in, phantom +48 and a sanken cs3e. i'll do the same with the other channels. usually i plug the sanken on channel 1 and wireles receivers on the other two..
i'll let you know,

pietro
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Old May 5th, 2008, 11:00 AM   #4
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My 442 exhibits some hiss when the inputs don't have anything connected - such open circuit noise is to be expected (noise figures are measured with the inputs shorted). Have to run the gain all the way to the top on both the input channel and the headphone monitor though
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Old May 5th, 2008, 02:45 PM   #5
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Here's what I observed with my 302, nothing connected, running on 3xAA, testing one channel at a time, dyn/flat:

For each channel I turned the fader to max then the gain to max before returning to zero and moving on to the next channel. As expected, there is some noise:

Channel 3, just "air" type noise, as I would expect. Same on Channel 2. Channel 1 - cranked all the way up, sounds like there's a bee in there! Slightly surprising, and worth noting for future reference. I'm not particularly concerned though, I still get excellent SNR even with that bee in there .... !
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Old May 5th, 2008, 03:26 PM   #6
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I made a recording with absolutely nothing connected apart from HD-25 headphones (stuck a mic in the cans) and running on internal 3xAA.

http://www.archive.org/details/Sd302PreampsNoiseTest

(yeah, I didn't have anything better to do tonight)
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Old May 5th, 2008, 04:23 PM   #7
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hey mike

I'M NOT ALONE!!!
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Old May 5th, 2008, 06:04 PM   #8
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Take a 150 ohm resister and solder across pins 2 and 3 of a XLRM and plug into mixer with Phantom off. All 3 channels will be equally quiet.

Last edited by Brooks Harrington; May 5th, 2008 at 06:40 PM.
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Old May 5th, 2008, 06:18 PM   #9
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STOP THE BUS NOW!

Gentlemen, you are operating the mixer in a way that it is not supposed to be operated. Will it hurt the mixer? No. Can you make any assessments about how well the input is working? Not really.

ANY, repeat, ANY mic or line level input want to be terminated properly. That means a mic or line level device must be plugged in. It doesn't have to be powered up, plugged in will do.

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Ty Ford
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Old May 6th, 2008, 02:28 AM   #10
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Quote:
Originally Posted by Ty Ford View Post
STOP THE BUS NOW!

Gentlemen, you are operating the mixer in a way that it is not supposed to be operated. Will it hurt the mixer? No. Can you make any assessments about how well the input is working? Not really.

ANY, repeat, ANY mic or line level input want to be terminated properly. That means a mic or line level device must be plugged in. It doesn't have to be powered up, plugged in will do.

Regards,

Ty Ford
Good point, I hadn't really considered that with nothing on the input it's just an open circuit ....
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