Miking small tube combo ....

MrBoogie

MrBoogie

New member
I recently scaled down from a half stack to a small 1x12 combo (Mesa F30). Today was my first attempt at recording it. Strange thing is, with the amp on STANDBY, as I move my sm57 closer to the speaker it starts to pick up a hum (sounds like 60hz hum I believe) at about 6 inches or so.

Things I tried to fix it:
1) tried a better mike cable, actually tried 3 different ones just in case
2) plugged into a different outlet / move the amp to different locations
3) (well, I don't have another dynamic mike to try)
4) plug an extension cab into the amp and miked that instead.

#4 is the one that worked for me. This leads me to believe that with such a small combo, when putting the mike up against the speaker cloth, it is close enough to the power supply to be affected by the transformer. Is this correct? If so, I guess this is my only choice for miking this wonderful sounding little amp. So much for scaling down :-)

Is this a common problem with really small tube combos? I never had this issue with any ss combos I had in the past.... of course those didn't need the sizeable power section that this little beast has.

MrBoogie
 
MrBoogie said:
Is this a common problem with really small tube combos? MrBoogie
Click to expand...


i've never had this problem, combo, tube, solid, or otherwise.


(wish i could help)
 
Thanks for the replies.

No, the amp isn't fan cooled. I think I'll get a hold of Mesa Boogie and see if this is normal for this amp. If not, I assume they'll replace or fix it.
 
See if your recording equipment and amp are plugged into the same circuit. Sometimes just moving to a plug on the other side of the room can help. Or, if you have lights with dimmers installed, see if adjusting them makes a difference. It might not be the amp at all.
 
I just found out the problem. There's something wrong with my sm-57. I don't know how that could be, but it is.

I just got an e609 and it doesn't pick up the noise - which seems to be 60Hz hum- that the sm-57 picks up when I put it near the amp, especially up higher near the electronics. Also, I switched cables and still only the 57 picks up the hum.

Any home-brew audio-physicists care to explain how this could be happening?

Anyway, I guess i'll be getting a new sm-57 and hopefully it won't have the same problem.
 
Probably induced hum from the transformer in the amp. As you move the mic into the magnetic field created by the transformer, the hum comed up. Some gear is just more sensitive to EMF than others.
 
MrBoogie said:
I just found out the problem. There's something wrong with my sm-57. I don't know how that could be, but it is.

I just got an e609 and it doesn't pick up the noise - which seems to be 60Hz hum- that the sm-57 picks up when I put it near the amp, especially up higher near the electronics. Also, I switched cables and still only the 57 picks up the hum.

Any home-brew audio-physicists care to explain how this could be happening?

Anyway, I guess i'll be getting a new sm-57 and hopefully it won't have the same problem.
Click to expand...

Did you get this microphone new or used? It sounds like maybe it's wired wrong.
 
I got the mike new at GC a long time ago....I think around '93. I was using it with my 4-track. In '96, I started gigging a lot with it, too. It probably got beat around/dropped. If it's wired wrong, it was always wired wrong. I looked inside and there's 2 wires coming from the mic element, and it goes into a glob of what looks like epoxy. I assume the electronics are engulfed in that stuff. I did wonder if it was wired wrong, except I've used it for years and never noticed this issue - of course this is my first really small combo (that I've tried to record) and with my other amps the mike was probably never in such close proximity to the amp's electronics.

I've considered the shielding issue, too. But it doesn't look like there's any shielding....maybe the metal body acts as the shielding? Or maybe it's shielded in the same area as that big glob of epoxy, and I just can't see it. Plus, it would be RFI shielded, NOT magnetically shielded, right? So that would not make any difference??

Thanks for all the replies! I'm finally able to record this amp without issues; and that's good, because it's the biggest reason I bought it. When I get a new sm-57, I'll let ya'll know if it does the same thing. If it doesn't, maybe I'll send my "bad" one to one of you so you can dissect it.

MrBoogie
 
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