MBHO CK12 Capsule--KA1000N and KA1100?

[telewulf]

Keep track of the polarity!

Oh yes, by all means! Especially if you have set up more than one mic and feel that 100 Hz and below does matter

Study the capsule connection and polarization in some different classic schematics

For easy comparison may I offer the drawings that I made again? As Khron pointed out in another thread, they are very simplified und not flawless but I think, they show the principals of the matter.

best wishes for Christmas from Bremen,
Wulf

 

[tomas.borgstrom]

I recently rebuilt a WA47 and connected the new capsule (Arienne Audio K47flat) like C12 but got a substantial low rumble. When I switched to the way it is connected in M49 it dissappeared.

Does anyone have an in depth explanation to why some connections might not work for some capsules / circuits?

 

[gyraf]

..some of the connection schemes require separate packplates..

 

[Voyager10]

I recently rebuilt a WA47 and connected the new capsule (Arienne Audio K47flat) like C12 but got a substantial low rumble. When I switched to the way it is connected in M49 it dissappeared.

Does anyone have an in depth explanation to why some connections might not work for some capsules / circuits?

In the C12 the amplifier input (tube grid) is connected to the backplate, and the diaphragms are held at fixed voltages. The backplate itself is pulled to +60V via a high-value resistor.

In the K47 the backplate is the entire capsule body, which means the saddle it's mounted on has +60V, and very sensitive electronics, on one side and ground on the other, where it's attached to the mic body. If the insulation isn't perfect (dirt, or even the plastic itself) a tiny current will pass from +60V to ground, and that will be picked up as a noise signal. It's low frequency most likely because the capsule capacitance will form a low-pass filter.

Generally you want as little 'stuff' as possible between the capsule connection and the head-amp input, because any leakage path to a voltage source will cause noise, and stray capacitance (basically any conductor physically near to any other conductor) will attenuate the signal.

 

[Voyager10]

For easy comparison may I offer the drawings that I made again? As Khron pointed out in another thread, they are very simplified und not flawless but I think, they show the principals of the matter.

That's a great summary! I spotted a couple of errors:
- on U87 the first 0.47n capacitor connects the two diaphragms directly, not via a 1G resistor.
- on U87A, there's a 0.47n capacitor between the two 1G resistors, to couple the two diaphragm connections in fig-8 mode
- KM86 isn't quite right, the head-amp input is connected to the backplates.

Who knew there were so many solutions to the same problem?