The AKG C-*414B*-ULS Capsule Swap Scenario

OK...

I put an Apex 430 cardoid capsule on a C414b-ULS body and the output is far less than the original AKG capsule.

I have tried wiring, re-wiring, and even feeding the capsule an external bias voltage, but the output is still low and tinny to the tune of @ -27db below the original capsule.
:?:
Any particular reason why this would happen? Are the capsules THAT different? YIKES. Perhaps that would explain the noisy-as-hell China condensers...

Or am I just missing something important?

i dunno but i've always wanted a few 414s to be able to play with.. must be nice to be able to tear one apart! :green:

I don't think the china condensors are all that bad, but likely the circuits are somewhat tuned to the type of capsule. is the 414 center leaded or on the side? what about the new capsule?

I have a spare set of 414 guts....

The Apex 430 (Same as Carvin CM-80) is a standard center lead cardoid @1" capsule. The rear diaphragm has no conductor sputtered on it.

The 414 is side leaded with four wires heading up to the capsule. Oddly enough, tests in cardoid mode with the C414 show that the diaphragm was polarized @30V. This is with the original capsule.

Side note: Perhaps I SHOULD polarize the diaphragm of the CM-80 cap??

The main functioning bias voltage was a full @62V before it was split off into halves by a voltage divider to head into the two different backplates (or diaphragms?) Cardoid mode just bypasses sending voltage to the back half of the capsule.

So now, I'm polarizing the Apex capsule with @30V, but was thinking about modding the voltage divider to polarize the cardoid capsule with more like @50-60VDC...

One More Thing
I know I've seen a picture of the 414 layout somewhere... I already have the schemo thanks to the moderator's website...

[quote author="northsiderap"]OK...

I put an Apex 430 cardoid capsule on a C414b-ULS body and the output is far less than the original AKG capsule.

I have tried wiring, re-wiring, and even feeding the capsule an external bias voltage, but the output is still low and tinny to the tune of @ -27db below the original capsule.
:?:
Any particular reason why this would happen? Are the capsules THAT different? YIKES. Perhaps that would explain the noisy-as-hell China condensers...

Or am I just missing something important?[/quote]

Are the resistors in your C414 3 gig or more ? The ones in the Apex might only be 500meg or 1gig max.

You are far away from the answer math is needed

An AKG ck12 is about 100pf a side and a 67 type about 55pf a side

Capsule Voltage times (delta cap change / total cap )


Read the neumann PDF "Microphones"

China capsules are not more noisy the design matters of the circuit. You need to understand the interface of the capsule to circuit.

How are you measuring the polarizing voltages? Just about any meter will load the supply and produce low readings.

I forgot about the RC of the capsule and the polarizing resistor... Oops. I tend to forget the some of the basics sometimes in my frenzied soldering sprees.

I am measuring with a decently high-impedance fluke DMM. I agree; it sounds reasonable that with a 3-gig per side polarization network there might be a drop in measurement accuracy.

Perhaps I should try to bypass the entire voltage divider with my own polarizing resistor. I will have to disconnect the capsule and measure the capacitance of that to determine the proper size for linear down to @20-25Hz.

I didn't mean that China capsules were noiser in themselves, I was suggesting that perhaps inferior damping network and sputtering manufacturing could lead to significantly lower output levels. Thus, the added noise would be in the makup gain needed in the mic head or following preamplifier.

The mic sounds good with little noise at all, allowing added makeup gain to be applied while still maintaining a reasonable noise floor.

Apart from very obvious bass rolloff and low output it is sounding OK.

Chinese capsules are getting better everyday, soon we will have nothing to complain about except our own lack of understanding. Gus have you tried the 6021 sub triode in your TCM if not give it a shot.

Analag