Recently I purchased a Sound Devices USB Pre and a Shure SM10A microphone. The mike worked fine while I was going through my Mackie 1402-VLZ mixer into the line input of a Gateway 9100 laptop. The signal to noise ratio was quite acceptable as the sound floor stayed at about -50. Now with that mike plugged directly into the USB Pre the best sound floor I can get is about -30 and that isn't acceptable in my line of work.
The USB Pre works great with a Electrovoice N/D 357B plugged into it for the sound floor stays at about -60. If either of you have recommendations please let me know as a head worn mike is extremely helpful in my recording environments!
The output level of the SM10 is 15 dB less than the EV 357B. This is due to the much smaller magnet used in the SM10.
Your options are:
1. Insert a mic preamp between the SM10 and the USB Pre.
2. Ask Sound Devices if the USB Pre can be modified for more gain.
3. Use a step-up transformer like the Shure A96F if the input impedance of the USB Pre is 10,000 ohms or greater.