MXL microphone circuit simulation, how to simulate the capsule?

[MKown]

Hi guys,

could someone help me with simulation of MXL microphone circuits?
Am using multisim and ltspice and i have some issues with mxl 2001/v67 and mxl 603/990 circuits.
Most of the circuits found on the forum, traced by the members, have capacitor in place of the capsule.
I couldn't find any electrical circuit equivalent for the capsule.
Also, do i proper powered microphone ?
Here's an example of the circuit:

 

[MKown]

Is there any of the below connections proper? Or should i use only ac source without capacitor?
I want to trace preamp characteristic, to understand which parts and how affect on de-emphasiss eq, but for now i have some issues.

 

[Matador]

Here how I do it:  remember, Neuman gives a hint with their "calibration input" node, which is right where the 560ohm resistor is (which MXL copied):

 

[MKown]

Thank you very much Matador :-*

Do you have other example for circuits like mxl 603 (schopes type) - without feedback? How inject in those?

How do you modeling transformer in multisum? With standard ms "audio transformer" 4:1 or 10:1 i'm getting weird low/middle cuts at the output... When I used virtual transformer with turn ratio 1 and resistance 160r primary 50r secondary i get the 2:1 finally, but i'm not sure is't proper working...

The last question is about mxl 2001 circuit If i would like to use one resistor to bias the fet and  put 1G (R5 on your schematic) resistor to ground like in u87, how should I connect potentiometer to verify proper resistance? 1 and 2 leg of potentiometer to the source and 3 to ground?

Thanks again!

 

[RuudNL]

Are you sure the 10 nF (left-top) is correct?
As far as I remember Neumann used 33 or even 47 nF.

 

[MKown]

Are you sure the 10 nF (left-top) is correct?
As far as I remember Neumann used 33 or even 47 nF.

Hello  RuudNL,

10nF is probably residue from chinese microphone versions
As you visited this thread, could you look on my newbie questions from the previous post.
I've read many of your posts, so i assume this would be some obvious things with your knowlege

 

[RuudNL]

About the test configuration: I agree with Matador, you should inject the test signal at the node R2/R3.
This is the way Neumann advises how to measure the frequency response of the electronics in the U87 microphone.

 

[Matador]

How do you modeling transformer in multisum? With standard ms "audio transformer" 4:1 or 10:1 i'm getting weird low/middle cuts at the output... When I used virtual transformer with turn ratio 1 and resistance 160r primary 50r secondary i get the 2:1 finally, but i'm not sure is't proper working...

I don't quite remember:  but you need to specify primary H at least so the sim knows what the bass response will look like.  LTSpice lets you specify both resistance and inductance (and parallel capacitance for that matter).

The last question is about mxl 2001 circuit If i would like to use one resistor to bias the fet and  put 1G (R5 on your schematic) resistor to ground like in u87, how should I connect potentiometer to verify proper resistance? 1 and 2 leg of potentiometer to the source and 3 to ground?

Thanks again!

You mean substitute R6 in my schematic with a pot?  Yes, 1-2 to source, and 3 to ground.