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Thread: Phantom power for one mic makes other mic quiet

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    Phantom power for one mic makes other mic quiet

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    I am a newbie to this forum and also to recording. Just getting started with learning to record acoustic guitar with a microphone into a Focusrite Saffire PRO 14 with Garageband. SM57 sounded okay but I just received an SM81 yesterday. There are aspects I like of both, but neither one is wowing me. Of course I have more experimenting to do, but wanted to try recording through both at once to see how that sounded. The SM81 requires phantom power to be engaged on the Focusrite, but once I engage it the SM57 immediately gets quieter. Is this just a Garageband issue? Or is this a common thing to have phantom power make a mic that does not require it get quieter? The SM57 records just fine until I turn the phantom power on and boom it goes extremely quiet in Garageband. The signal to the Focusrite seems just fine based on the lights on the interface, as well as the lights in Saffire MixControl. Any advice is most appreciated!

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    Subscribing to see how this turns out. Never had this happen in any of the gear I've used.
    Welcome to the site by the way.
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    If the level on the meters on the SM57 channel drops seriously when the phantom button is pressed, something is wrong. The only thing I can imagine is that the phantom power circuit itself is either faulty or poorly designed. It is true that the presence of the two resistors across pins 2 and 3 does pad the microphone but it's a very minimal change - a typical 57 is around 300Ohms or so, and this probably changes to 295 Ohms - a tiny and insignificant change. However, there's a tiny chance of a fault - but its hard to imagine how the phantom pair of resistors could both be short, or virtually short - it would still leave one at 6K, making a small change to the impedance. The software has no link to this - so it's a mystery. Does it happen if you swap the two mics around? The SM57 will need more gain of course than the condenser, which will be much louder - but if this gain chances when you hit the switch, something is clearly adrift. I'd drop Focusrite an email.

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    Thanks for the response rob and thanks for the welcome mixsit! I ended up emailing Focusrite and they suggested resetting the Saffire MixControl utility back to factory, even though I don't believe I ever tweaked anything in the past. It did indeed fix the issue of the phantom power switch dropping the SM57 level way down to almost nothing, so I guess it was just a strange glitch with the interface. As rob mentioned, yes the SM57 is still quieter, but I understand now that this is normal and recording with both of these mics at the same time may not be a good option. Even with cranking the gain on the SM57 channel, it seems difficult to balance the two mics together. Back to experimenting!

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    What are you using the mics for? 57 for vocal and 81 for acoustic?

    The SM57 is definitely on the lower end of sensitivity but I can get an acceptable level with my Saffire Pro 26, which I'd bet a buck or two has the same preamps.

    Just set the faders in the DAW so the levels match if you are trying to monitor, and having trouble. You can always reset those or adjust the track's gain after recording to make them more equal, though you should be able to just dial the gain on the F'rite back for the condenser channel to match the SM57, and still have a mixable level signal.

    P.S. GarageBand on a Mac I assume - there's also a Recording Level setting for the track. I never actually messed with that myself because I don't recall it being there on the earlier version of GB I was using before switching to Logic Pro X, but you should be able to use that to equalize the tracks, too?
    "... I know in the mornin' that it's gonna be good
    when I stick out my elbows and they don't bump wood." - Bill Kirchen

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