Guitar amp sound distorted when miked up

Question

I am trying to understand an issue I have when I record tubed guitar amps on the distortion channel with a standard SM57.

I always feel like my miked sound is much more distorted than the actual sound coming out from the amp speakers. For example, an ideal sound by ear might be found setting the gain to 8, but to replicate the same distortion level in the miked sound, I might have to turn it all the way down to 2. I am also positive that the mic signal is not clipping on the pre.

I suspect that a couple of different factors may be implicated such as:

• microphone distance to cone
• microphone placement on cone
• pre-amp level to amp level difference (having the amp cranked up and the mic low gain versus having the mic gain cranked up and amp low volume)
• room reflection (my amp is on the floor rather off the ground)

etc...

Any clarifications are much appreciated!

Answer 1

I usually find that SM57s accentuate distortion/tinniness when the mic is pointed at the center of the speaker cone. My preferred placement is 45 degrees off-axis, aimed between the outer edge of the cone and the outer edge of the speaker. Tends to give a fuller reflection of the "sound in the room"... I'm not sure that this would totally mitigate your issues with recorded signal distortion, but maybe part of the problem is overtones/noise outweighing the richer frequencies on other parts of the speaker.

In any case, experimenting with mic placement seems a viable first alternative to swapping gear, IMO.