Mic Noise

imacgreg

New member
Hi all,
I just did a little test with my 11 humble mics by recording 5 seconds of silence with each and then 10 seconds of "jangling" keys. The ultimate reason for doing this is that I am bored and our drummer doesn't want to record today. Anway I didn't find much except that my Marshall MXL 2001 has a HUGE hum at 75hz. Not to say I was too surprised (although my 603's did much better), but I want to know how to fix this. I am an electronics student, so feel free to elaborate technically. New xformer, replace electronics? I have been thinking about the Royer mod, but I just haven't gotten to it yet. Until then, any suggestions??

Thanks in advance,
Ian

I think my easiest solution would be to just buy a C1 anyway...
 
Put sheet music in front of the mics. Maybe they're humming because they don't know the words. :)

But, if both mics are humming, it's probably an induced hum pickup. Try moving them around and see if the hum gets louder or softer. If you can lower (or eliminate) the hum by moving the mics around, you have a grounding/shielding problem in your room that needs to be fixed.
 
Ahhh, that's different. That sounds like poor grounding in the mic, which is pretty easy to fix. Make sure the brass body and the grille section are solidly grounded to each other, and to the core of the mic. You may hafta take the mic apart and sand a few places down to bare metal to make sure of a good connection.
 
Harvey - Could this be the source of a hiss as well?
I'm still desperately trying to make use of the bloody Nady I payes 80$ for, last time I was in the US, and hisses like crazy....
Bahhhh.



Oren
 
Oren,

Sorry, but hiss is the result of the internal electronics. In this case, probably some low quality resistors, and cheap FET transistors. You could use Scott Dorsey's MXL-2001 preamp board mod, and lower the hiss dramatically.
 
Harvey Is The Man! (HISM)

Harvey,
I took the round shell off, scraped all the paint off of where I could see it contact the chassis, put it all back together and fired it up. The loud 75hz hum is gone! I also heard another quiter hum, but I found out that it was due to the mic stand and computer both being on my hard desk. I guess the computer was vibrating enough that the mic picked it up, and not having a shockmount doesn't help either. Overall your advice was just what I needed and my mic isn't as bad as it used to be. I have now made a new internet acronym: HISM or "harvey is the man"

Thanks,
Ian
 
Shit, it worked??? Are you serious? It really worked? Geez, I'm gonna hafta try that one of these days myself. :eek:


How cool!!


Seriously though, glad I could help.

Don't be too hard on Marshall. It may have been fine at the factory, but somewhere along the way, it got bumped or jarred just enough, so that the ground wasn't solid enough and that caused the hum.
 
Harvey,

What exactly is that mod you were talking about? I don't think I would want to touch my pre-amps (They are on a Behringer mixer and work fine, so I don't want to Jinx it.. :-) )


Oren
 
Oren,

Scott's mod uses a new circuit board and higher quality parts to replace the circuit boards in the Marshall 2001. Pretty easy to build and install, and difficult to screw it up. The board and instructions costs $20 and the parts will be around $40.
 
Harvaey -

Hmmm.... Even if it *would* be relevant to a Nady CM-90, which I doubt, the pars and the plans cost almost as much as the mic did...

Thanks anyway!


Oren
 
This is the problem with painted mics. Anytime you paint a mic, there are going to be problems, unless the QC is flawless. We decided against painting our new B Series mics as a result of this problem.

Great call Harvey...you da man!

Alan Hyatt
PMI Audio Group
 
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