Troubleshooting gain problems between microphone and amp

Question

I have a micropohone and an amp, both of which I was recommended; I bought the former, because that was the cheapest option to experiment with.

Unfortunately, the two appear mismatched, since I have to crank up my gain to max in order to get the microphone to pick up the input.

• Amp: Focusrite Scarlett Solo
• Mic: Behringer XM8500 (dynamic)
• Software: Windows 8.1, driver software installed and installation instructions followed

Specs

Amp

Microphone Input

• Frequency Response: 20 Hz – 20 kHz +/-0.3 dB
• Gain Range: -4 dB to +46 dB
• THD: -97 dB
• Noise (EIN): -125 dB
• Dynamic Range: 106 dB (A-weighted)
• Max. Input level: +4 dBu

Mic

• Impedance: 150 ohms
• Sensitivity: -70dB
• Bandwidth: 50Hz to 15kHz

I’ve read about the science behind SPL and noise, but I can’t google my way to what determines the gain between the mic and amp.

While this is a cheap mic, I was told this was a perfect starter amp, but cranking up the amp to get a mic working seems like at least dynamic mics will be poorly served by it.

Can someone explain in the cold parlance science why my mic isn’t picked up properly, and how I’ll decide whether future mics are compatible (or, hell, even amps, if the Scarlett Solo is a dud).

I’m happy with how my Sennheiser HD600s sound with my amp, but I don’t know whether I can tell the difference—and I could be wrong, since I don’t know the science behind driving headphones to realize their full potential. (12-40,500 Hz, 300 Ω.)

Answer 1

That microphone is quite LOW SENSITIVITY. If you were a head-banging heavy-metal rock musician screaming into the microphone halfway inside your mouth you would see quite a signficant signal out of it.

And while Focusrite is a quite respectable brand of audio equipment, those smaller audio interface products are not noted for having premium microphone preamps with high gain and good signal-to-noise ratio.

So you have rather a poor-performing combination of low-output mic and low-gain mic preamp. If we knew what you are trying to record, it may be possible to offer some practical suggestions for improving the performance of your system.