I've been setting up a home recording studio in my basement. I have a brand new Shure SM58 dynamic mic that I bought, which I am inputting straight into an Mbox 2 USB interface, which connects to my computer. I am using Audacity in Linux to record the vocal tracks, via the JACK sound server.

Right now I am just trying to record a vocal track over an imported CD audio file (to make a demo). However, to get the vocal volume to a level where it is comparable with the audio track, I am having to crank up the Mbox input channel gain to almost max; add up to 10 dBs to the vocal track in Audacity and reduce the audio track by a few dBs.

The mic seems to work fine and the result sounds decent; however, I am just wondering if it is normal that I'm having to add all this gain to the vocal signal, or is it possible that perhaps something is not right?

  • 2
    There are a lot of SM58 copies about, which may not be as good as the real thing. Having said that, I'm currently using a genuine SM58, but I fitted it with a <£5 rip off capsule (without the transformer...). There's very little difference! SM58s are great for live stage work, but not ideal for recording. Comment, thus no answer.
    – Tim
    Commented Jul 23, 2018 at 17:46
  • @Tim Thanks for your comment. I'm fairly sure it is a genuine SM58 - the box, documentation etc. looked quite convincing). Yes, I've heard condenser mics are better for recording, but I got that one in case I want to eventually use it for performing as well.
    – Time4Tea
    Commented Jul 23, 2018 at 18:16
  • What input are you using... mic or line? How did you specify the mic should be supplied, with a mono jack on the end or an XLR. My first guess is you got a mono jack & you're trying to get a level-match through the line input... that's not going to go well, as you've already discovered.
    – Tetsujin
    Commented Jul 23, 2018 at 19:19
  • @Tetsujin The mic is XLR and I am plugging it directly into the XLR socket on the interface input channel.
    – Time4Tea
    Commented Jul 23, 2018 at 19:25
  • Then check if the interface knows to auto-switch, or if it's manual [& you switched it]. If you could post a link to the model number &/or pics of the front & back panels it might be easier to figure out. I don't know the MBox interfaces at all, I'm afraid, so I'm flying blind.
    – Tetsujin
    Commented Jul 23, 2018 at 19:28

1 Answer 1


That doesn't strike me as unusual. The SM58 is a dynamic microphone (i.e., “inverted loudspeaker” design), and the main reason it's so popular is that it can take quite a beating (both in terms of sound-pressure and mechanical abuse) without problems. IOW, it's not very sensitive. That doesn't mean it can't also be used for harmless sources like normal speech in a studio setting (in fact that's what it was originally designed for!), but it does require a lot of gain then. A good mic preamp should be able to offer that, but a built-in one on a cheaper audio interface may introduce a significant amount of noise if you try it.

In studio situations, for sources other than drums or electric guitar, condenser microphones are usually preferred. These have a much lighter diaphragm, hence are more fragile but also capable of picking up fine sounds more accurately. They need a phantom power supply, both for polarizing the capsule and for the built-in stabilisation stage; most audio interfaces offer that.

So, if you're serious about this you should probably invest in either a cheap condenser mic, or a decent mic preamp. (In the long term, in both.) For vocals, a tube preamp tends to make a lot of sense (it adds a bit of saturation harmonics when driven, which further adds power to the signal psychoacoustics-wise).

In the meantime, make the best you can out of that signal. For vocals, a decent compressor works wonders for bringing up the signal level. Audacity has one built-in, but its quality is unfortunately horrible. I recommend you check out Reaper, an excellent DAW that comes with good plugins for compression, denoising etc.. It's not technically speaking free software, but you can use the trial version just like that without problems.

  • Thanks for your answer - this is very helpful. Yes, in the longer-term, if I get more serious, then I will look at getting a condenser mic or mic preamp. I think this setup will work for now (for making demos), but just wanted to get some indication of whether this behavior is normal, as it's the first time I've done any microphone recording.
    – Time4Tea
    Commented Jul 23, 2018 at 18:36
  • I actually have a POD 2 guitar preamp, which I believe has a 'tube preamp' setting and a built-in compressor. Perhaps I could try putting the mic through that before the interface (although I assume I would need some sort of converter for the mic lead to 1/4" jack)?
    – Time4Tea
    Commented Jul 23, 2018 at 18:37
  • 1
    There's absolutely nothing inherently wrong in putting up a 58 for a vocal mic. I don't use them a lot, I would normally use a U87 [for obvious & expensive reasons] but I've used 58s when I need isolation from ambient track noise with zero issues.... & re: 'cheap condenser'... If you already spent $£€100 on a 58, why the h*** would you throw more money at an under-performing condenser? You can get a decent dynamic mic for 100... you can barely get a decent condenser for 10 times that.
    – Tetsujin
    Commented Jul 23, 2018 at 19:21
  • @Tetsujin it depends what sound you want. For rock or spoken voice, yes, a dynamic mic works well whereas many condensers may be liable to producing unpleasant sibilance. But as soon as you want a bit of “air” in the sound, even a 50$ condenser can beat all but a few dynamic models. Commented Jul 23, 2018 at 19:47
  • 1
    Then a tube mic preamp would probably be the best investment for you. Commented Jul 23, 2018 at 21:12

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