Preamp noise

[ok_computer]

Hi there. I was just wondering something about my USB Audio Interface and the preamps. I am using a M-Audio Mobile Pre USB Bus-Powered Preamp and Audio Interface.


I have tried recording with a Shure PG81 and a SM57 mic and am always getting a hiss/noise type sound in the background. I have the Gain turned up just over three quaters of the way. I have determined it's not the microphones or the XLR cables because it makes the hiss sound when nothing is actually connected and I'm just monitoring the output of the interface. I think it's just the fact that it's a relatively cheap preamp on the interface. I've tried moving the interface away from my Computer incase that was part of the problem but it doesn't make a difference. Is it common to hear a sort of hissing sound when the gain is set so high on budget USB audio interfaces?

I know that turning down the gain is an obivious answer, but does that mean I am losing resolution when recording? Sorry if that's a noob question but without the gain being set high (which unfortunately introduces noise) then I'm recording the signal too low and not hitting the aimed peaks of around -10 or so on the meter input levels. At the moment I remove noise with a Waves Noise reduction plugin which basically captures a noise profile. It works pretty well but was wondering if there's any other advice or tips for reducing noise. Would the noise be reduced with high gain settings if it was a 24 bit recording device? The M audio interface I have is 16 bit.

 

[RRuskin]

You are correct in that the preamps you have are less than ideal but you should be able to do decent work with them by respecting their limitations. Higher resolution is of little value if you suck up system noise along the way. Lower your input level so that you peak somewhere between -18 to -14. That's the ballpark range of analog "0" anyway. That should solve your hiss problem.

 

[ok_computer]

Ah Allright, thanks for the reply! I was reading up about pre-amp SNR's and was just curious about the SNR on my equipment. My current M-Audio Mobile Pre USB has a "Signal-to-noise ratio of -88dB, A-weighted". Would an interface with an SNR of "101dB" (such as the M-Audio Fast Track Pro) produce significantly less hiss with higher gain and result in better quality recordings? I mostly just use this interface for recording acoustic guitar with the Shure pg81 mic and trying to determine if it's worth the money to upgrade my USB interface and get a better SNR ratio with better dynamic range. (going from 16 bit to 24 bit)

 

[RRuskin]

Moving up to 24 bits will allow you to achieve higher resolution at lower input levels. That alone should improve things. I refuse to use any interface with built in pre's because of the compromises manufacturers tend to make to reach a price point. Everything in my rig is separate allowing much more flexibility and better quality right from the start.

 

[Nandoram]

I had the same problem and played with the XLR cables, the mike position, and the preamp until I figured out it was another piece of gear creating the noise. I was recording vocals, and I had a Digitech BP200 plugged into the power strip (but not in use at the time, and no bass plugged in to it). I unplugged the Digitech unit, and the noise was GONE. No problems when I'm using the BP200... but for some reason, it interferes with my Summit Preamp and Summit Tube Leveler when it's just "on". Sometimes, it's just another piece of gear!