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Thread: mystery mic

  1. #1

    Default mystery mic

    I have a GLS ES-57 dynamic mic (a cheap clone of an SM57) that works just fine when I plug it into the audio interface of my home recording setup, but not at all when I plug it into my VOX mini3 portable amp. I use the same cable with it either way. The problem is not with the amp, because it works just fine when I plug a cheap old Radio Shack mic (I think -- I bought it many years ago) into it.

    Any suggestions? I'd really rather use the GLS!

    George

  2. #2
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    Default

    George,

    I don't have the portable amp you are talking about. Does it have an XLR input for the mic? I assume the ES-57 has an XLR cable and your mic in on the amp is 1/4" - is that true?

    How are you converting from your mic to 1/4?


    The Cheap old Radio Shack mic is probably a high impedance mic meant to go straight into a Line In type plug.

    Your audio interface for your home recording setup probably has an XLR input with a built in Pre-Amp.
    Just guessing,

    The great thing about recording/audio equipment is that there is always something else that you need. What kind of outputs does your audio interface have? If there is a 1/4" line out, you could use your Audio interface as a pre-amp and put a 1/4" cord from the line-out of your audio interface into the amp.

    Doug
    Last edited by Doug W; 03-09-2014 at 04:35 AM.
    I am the best ukulele player on my block!

  3. #3

    Default

    Thanks, Doug, I think that may be it. I just tested the mic as you suggested, by plugging it into the audio interface (Scarlett 2i2, yes it has preamps) and running a line from the monitor line out to the Vox mic input. It worked like a charm! The GLS mic is definitely low-Z. The Vox has separate line and mic inputs, but I suppose my that experience indicates that both are high-Z -- I can't find any info that specifies this, but the old RS mic works equally well in either.

    But your comment raises another question I've been puzzling about. Does this mean that I need a full preamp, or would a DI box (to correct the impedance mismatch) do the trick? I'd really like to use the Vox to play in places where a power outlet is not handy, and I'm not aware of any preamps that are battery-powered, although plenty of DI boxes are.

    Great suggestion!
    George

  4. #4
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    Default

    George,

    D.I. box changes a High-Z signal into a Low-Z signal which a pre-amp can handle.
    Pre-amp takes a low-Z signal and turns it into a High-Z.

    My wife and I both have these old LRBaggs pre-amps which only run on batteries. They don't make the model shown in the picture anymore but if you can find one on Ebay or elsewhere used, I recommend it. I have never figured out a model number for these guys and don't see them around much. Using this model with a Low-Z mic requires an impedance transformer. The impedance transformer shown in the picture seems to run around $17.

    Have you looked at the LRBaggs Para DI? It is both a DI box and pre-amp. I am not 100% sure if it runs on batteries but I would guess that it does. Maybe someone else who has one can comment on it.

    LRBaggs.jpgImpXfmr.jpg

    Just get out the credit card and slide down that slippery slope into music equipment land.
    I am the best ukulele player on my block!

  5. #5

    Default

    Thanks! I already had (after I posted last) ordered a similar impedance transformer but I gather I'd need the preamp too. And I'll also check out the Para DI.

    George

  6. #6

    Default

    I received the impedance transformer (Shure a85f) today and it did the job. It plugs into the mic input of the amp, with and XLR-XLR cable between it and the mic. The mic sounds great.

    Thanks again for the help.
    George

  7. #7
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    Default

    Nice that you could get the job done without the added expense of a pre-amp.
    I am the best ukulele player on my block!

  8. #8

    Default

    Doug, I gather that a preamp might still be worth considering on down the road to improve the quality of the amp output, but for now I'm satisfied. I've used the system with our little (acoustic only) band at a couple of gigs now and it seems to be doing just what I wanted.

    George

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