Mic Parts 251 build issue…

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redddog

Well-known member
Joined
Feb 19, 2009
Messages
47
Hey guys. First build from a ACM 1200 mod. Did the whole shebang….RK capsule, circuit, switches.

I’m getting sort of a low rumble out of it. It seems to lessen the when I burn it in for an hour or so but when I go back it still has the rumble.

The mic parts dude told me to refer to the troubleshooting guide (which I have done - it’s not that robust).

Wondering if a “low rumble” would give someone with your level of expertise something of a starting point to look at first. All joints are good and there’s no real obvious build issues.

Thanks guys
 
Is it constant? 50/60hz? Changes when you move the mic? Any change if you blow gently towards the capsule?
 
Check if the whole body is properly grounded, grille as well. You haven't removed the inner, fine grille mesh?
 
totally. Understood. I’m wondering if that rumble could be a grounding issue?
 
Last edited:
I'm also thinking it related to the capsule and will add to double check that the capsule mounting screws and capsule holder mounting screws are tight.

In my experience a mechanical grounding issue results in a hum or buzz, not a low rumble.
 
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