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Help with vintage mic,Telefunken - SABA - AKG D77 gain and hiss

Discussion in 'Microphones' started by gamagros, Apr 5, 2015.

  1. gamagros

    gamagros Active Member

    Hello from Spain. I'm new in this forum and a newbie into recording,

    I'm starting to record using my Mac, Logic and Roland Quad Capture. Mainly I record electric guitars signal and midi stream. I have not used microphones before but USB mics.

    Now I'm trying to use a vintage stereo microphone (Telefunken - SABA - AKG D77) from a tube reel to reel recorder from the 60's. It has a 5pin DIN connector that I have split into two TSR mono connectors (not balanced). (The mic is identical to this one d77_223773.jpg

    Plugging this TSR connectors into the interface (Quad Capture) I get a nice tone for male vocals and for recording guitar amps. But I need to set the gain knobs to the max and then a hiss noise from the interface appears. I'm pretty sure that the noise is from the interface and not from the microphones 'cause it doesn't change when I plug or unplug the connectors. I think it is a normal noise when setting gain to max.

    I hope I can adapt these vintage mics. They work fine with the vintage tape recorder, so I think it is only a problem of adapting the signal.

    I have found info about cheap mic preamps, do you think that is what I need to remove the hiss raising the signal level?

    Thanks in advance,

    Gabriel
     
  2. DonnyThompson

    DonnyThompson Distinguished Member

    It could be that the gain of the preamp you are using - the quad capture - isn't sufficient enough to gain the mic up without introducing noise at the same time.

    The mic isn't a condenser, at least from what I read on the spec sheet, which would most likely make it a dynamic, and depending on the impedance/output, it might require a lot of gain to run at its intended optimum.

    I don't know anything about the Quad Capture you have, but my bet is that it doesn't provide enough gain to power the two elements. If you are using the TRS inputs, the gain could be even lower.

    I would try this through a preamp that has more gain, say something in the neighborhood of 65db. You could also try a Cloudlifter, which is a preamp with a set gain of +25db between the mic and the Quad Capture.

    This might be enough to gain the signal up sufficiently so that you are hearing more signal than noise.

    FWIW

    d.
     
    pcrecord likes this.
  3. gamagros

    gamagros Active Member

    Thank you very much. In the while I have read the specs of the interface and the TRS are dumped with triple of impedance, so I'm going to change the connectors from TRS to XLR before I try a preamp or a Cloudlifter.

    Thanks again
     
  4. Boswell

    Boswell Moderator Distinguished Member

    The significant point is that the TRS inputs of the Quad Capture have a 10dB pad on them relative to the XLR inputs, so the pre-amps are having to work really hard with the dynamic mic outputs going into the TRS line inputs.

    If you are considering taking the microphone outputs directly into the XLR inputs, take great care both in how you wire up the single-ended outputs of the microphone into the balanced XLR inputs and also that you ensure you never have phantom power switched on. If possible, use 1:1 microphone transformers between the microphone outputs and the pre-amp's XLR inputs, as this will perform the necessary unbalanced-balanced conversion and also protect against inadvertent phantom power application.
     
    DonnyThompson likes this.
  5. DonnyThompson

    DonnyThompson Distinguished Member

    I looked up the specs on the Roland Quad, apparently the max gain is rated at 50db. While not in the "basement" per say, that's pretty low in comparison to most other modern pre/i-o's.

    My bet is that the Quad was built for primary condenser mic use, and while 50db is sufficient for condensers, it's pretty low for many dynamics. And, as Bos and I both mentioned previously, using the TRS input is knocking that gain down another 10db, making your total gain 40db ...max.

    That's pretty low. Also, because the stereo mic is really two elements wired together, ( see spec sheet you provided) you are essentially having to share that gain between two dynamic mics.

    You're having to crank that Quad to its max, and work it so hard just to get a perceptible signal, which is why you're ending up with a lot of noise.

    FWIW
     

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