Need help diagnosing low gain on LDC mic

Discussion in 'Microphones (live or studio)' started by GuitarTim, Apr 20, 2005.

  1. GuitarTim

    GuitarTim Guest

    I bought my first condensor mic a couple weeks ago, and while I haven't had much time on it yet, one thing I have noticed is that I seem to have to crank up the gain on the pre in order to get any real level. Hoping I can find some answers here as to whether the issue is with the mic or the pre.

    The mic is an Apex 415 - this mic has a low-cut switch, a -10db pad switch, and 3 polar patterns (cardioid, omni, figure-eight).

    The pre is a Steinberg MI4 USB interface. I have used several different dynamic mics with this setup, and always got a decent input level with the gain up only about 1/4, but with the Apex, I have to put it up to what would be 8 or 9 if there were numbers on the dial. The interface has integrated preamps on the balanced inputs, and supplies 48v phantom power (which of course I'm using with the Apex, but not with the condensors).

    Any idea how I'd know if the gain issue is with the mic or the pre? I do like the SOUND of the mic, and also I'm not really sure if the gain thing is really an issue, since I don't have a "studio", and my room (family room) would be considered screamingly noisy by studio standards, so the fact that I don't get a lot of "extra noise" when recording is actually a plus in my case. I'm thinking that this setup will be fine for the time being, but if I wanted to upgrade, I'm wondering which would be a "better" purchase... a new mic or a new pre (the MI4 is a given unless I upgrade to a different version of Cubase, since my version will only work in the presence of the MI4)...

    Any ideas? Thanks!
  2. Dave62

    Dave62 Guest

    I assume you have the -10 pad disengaged. If you have a multitester you could chek the 48 volt power. Pin 2 to ground (pin 1) and pin 3 to ground should both be at least 44 volts. Less power to a condensor means less output. Is there excessive noise floor in your recordings with this mic? If your vocal is peaking at -5 dbfs the noise floor should be between -60 and -90 dbfs. Much higher(less than 60) and there may be a problem. If the noise floor is acceptable there is probably nothing wrong.
    You can use a differen't preamp with the MI4, you run a balanced line out of the other pre and into the 1/4 trs balanced line ins 1&2 of your unit. Input gain should be fully left to do this.
  3. GuitarTim

    GuitarTim Guest

    Thanks, Dave. Yes, I made sure the pad is not engaged. I tried some tests last weekend where I made sure I correctly had the "front" of the mic identified, and tried it in all 3 polar configurations, tried it with the pad on, and with the low-cut both on and off. Didn't seem to make much difference.

    I do have a multitester, so I will check the voltage (can you detail exactly where I need to stick the probes?). Not sure how to check the noise floor, or even exactly what you mean...
  4. Dave62

    Dave62 Guest

    The phantom power is supplied by your usb box so you chek the power levels at the female XLR pluggin on the back or at the end of the cable that you plug in to the mic. You should chek both to eliminate the cable as a problem. You should be able to see the pin numbers on the xlr jack.
    As to the noise floor, record a vocal thru the mic setting the input gain so it peaks in your software around -5 dbfs. Then have a look at the average noise level peaks where you are not singing. Most daws have a peak reading setting for input and you will have to find that to chek these things. The thin band of signal is your noise floor and in a reasonably quiet room should be down 60 db or more when your not singing.
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