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Author Topic: C-24 RF in the movable capsule  (Read 2779 times)


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C-24 RF in the movable capsule
« on: April 24, 2011, 02:42:42 AM »

I've been wrestling with my C-24 for years. It's gotten to a love/hate  relationship. It's  a pristine looking early model, the stationary capsule sounds great but I cannot get rid of the RF coming from the movable capsule and it's not subtle. I have replaced the cable (not a fun job)..no difference, I changed the tube, no difference,..I have added grounding wires within the mic to compensate for the abysmal grounding setup in the mic, much better hum performance but still RF. I  even tried bypassing the grid of the tube with 10pf to ground and the RF got louder! I recently removed the signal going to the grid of the tube for the movable capsule and the RF was gone..that leaves a few polarizing resistors and the capsule.. Could the capsule be doing this??..I have a good ground to the movable windscreen and the metal support around the capsule..What am I missing???

Steve Addabbo


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Re: C-24 RF in the movable capsule
« Reply #1 on: April 24, 2011, 03:04:30 AM »

You probably have missing what many C24 mic systems have missing: a comprehensive, thorough grounding and shielding scheme. AKG was notorious for this in its tube mics, especially in the C24 which took the price for non-sensical (and constantly changing) grounding and shielding.

Bottom line: The entrance point for RF is somewhere where the shield is interrupted. You need 100% shield coverage from head basket to XLR shell at the input of your mic pre/mixer. An Ohm meter will not show this, only thorough visual inspection of ALL connections, from the mic's cable connector to the final XLR, all housing parts of connectors must be connected to ground AND cable shields. NO exception.
Klaus Heyne
German Masterworks®
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