R/E/P Community

R/E/P => Klaus Heyne's Mic Lab => Topic started by: pinkphiloyd on December 14, 2014, 05:41:14 pm

Title: Mic modding newbie, RF issue, please help.
Post by: pinkphiloyd on December 14, 2014, 05:41:14 pm
Hey everybody.  Long time DIY tinkerer.  I recently decided to try modding microphones just for fun.  So I did some reading, then purchased a Studio Projects B1.  I replaced the capsule with an RK-47.  great.  I also, as I had read in several different places, removed the inner layer of mesh from the head basket.  Not so great.  I'm getting an annoying level of RF interference now.  I'm chalking it up to learning and that's a mod I won't be performing in the future, but does anybody have any suggestions for correcting the mistake I've already made?  Thanks so much.
Title: Re: Mic modding newbie, RF issue, please help.
Post by: klaus on December 14, 2014, 09:37:37 pm
Though there is a point where RF will intrude through the weave of a head basket whose weave is too coarse, the fact that a C12 with its large square single-weave does not exhibit this behavior is an indication that you may want to first investigate a few other RF gremlins (which, though you successfully kept them at bay with your second screen, may have been lurking just below the surface all along!):

1. mic connector/cable termination
If the SP mic uses an XLR connector, make sure that the chassis and mic housing ground are tied to pin #1 of the XLR. Also make sure that on BOTH connectors of the mic cable you use with this mic, pin #1 (ground) and the cable's shielding wire are connected to the connector's housing lug.

A simple test whether you have succeeded in all of the above:
Plug the mic cable into the mic, but don't plug the other, male side into your mic pre/mixer/phantom supply. Just leave it hanging. Hold one probe of a DC resistance meter to the sleeve of the male XLR connector, and the other probe onto the head basket of your mic: if the meter reads zero ohms, you have pretty much done all you can with properly terminating your cable and connectors.
But if it reads open, you need to investigate where the mic's shielding/grounding is broken. For example, you may have lost the basket's ground connection to the mic body when you removed the inner mesh, which may have been soldered to the head frame, thus grounding it. Or you incorrectly terminated the connectors.

2. Head assembly grounding
I have found on some mics with minimal capsule head shielding from a (wide, open) basket that grounding the capsule mount helps. This is especially true for the first generation of C24 mics which often suffered from RF, and which became quiet after grounding the head assembly.

Title: Re: Mic modding newbie, RF issue, please help.
Post by: pinkphiloyd on December 14, 2014, 11:37:59 pm
Okay, I'm gonna try this.  Thanks!
Title: Re: Mic modding newbie, RF issue, please help.
Post by: Jim Williams on December 16, 2014, 11:57:24 am
I have one of those, a real POS. Mostly plastic, I'm suprized they work at all. Yes, mine is also noisy. A low ohms DVM is your friend, but Ebay or Craig's List is your solution.