Schoeps circuit de-emphasis - a new approach

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xeawr

Well-known member
Joined
Dec 14, 2016
Messages
166
Location
Germany / Austria
maybe this is a better way to implement a de-emphasis for cheap generic K67-type capsules. What do you think?

(see resistor values in red)

mxl990-schoeps-deemph.jpg


Together with the 22n caps that makes a -3dB point of about 15kHz (going from memory here). At 20kHz this would be about 4-5dB of attenuation (again going from memory), sounds about right for a cheap K67 capsule.

This is not my "discovery" or idea, I saw this first in a video on youtube where a guy reverse engineered the FAME CM2 microphone. Have a look at the output resistors: there are two 470 ohm.

bildschirmfoto-2020-04-22-um-14-55-04832.jpg


What do you guys think?
 
Without looking more closely I’ll speculate the effect will vary wildly with the type of preamp load, since it’s not isolated from it. 
 
Unfortunately this guy got it wrong.  The Fame CM2 is built with SMD-components and the part in doubt is a resistor which is marked with "470" wich means a 4 a 7 and zero 0, which is a 47 Ohm resistor and NOT a 470 Ohm resistor.  Even then the circuit is wrong because during cloning the clone of a  clone of a schoeps-circuit, someone got it wrong and confused a resistor with a coil which is originally there instead of the two resistors.  You shouldn't watch so much videos of unskilled people - it will save you a lot of time.
 
Yes, as EmRR already said, the increased output impedance of the circuit is a bad idea and makes the result unpredictable.
Besides that, -3 dB @ 15 KHz may not be enough in some cases.  5 to 6 dB @ 15 KHz seems more realistic.
(The U67 for example uses -7 dB @ 16 KHz.)
 
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