Help for understanding a Chinese U87 fake microphone schematics

[Khron]

This is a really quick build, but it works.

Have you checked / measured what the current consumption of this oscillator is?

 

[Cqwet Dbdfte]

Have you checked / measured what the current consumption of this oscillator is?

The plug board test adds a lot of parasitic inductance and mutual coupling, a tight PCB layout would have to consider this.
My sims were running at a few MHz

 

[Cqwet Dbdfte]

The voltage generator sim works. I had to mess with it. Takes long time. FZT857Q (ZTX857) does a good job here.
Using two inductors in series limits voltage stress on each part.
If a parasitic loss across the inductor is used the sim takes a very long time. That loss is central in determining the output voltage.
Maybe I'll get those parts and make a board...
EDIT:
Using two 68uH coils in series p/n 744764168 (SPICE model includes 162kOhm loss each) seems to work OK.
Should increase chance for success.
732-744764168CT-ND
The SIM below has no inductor loss.

 

[Екатерина]

I have the mic lying around for a while now, but haven't got around doing anything with it yet. But I'd expect the circuit to be way more linear and less coloring than a real U87 circuit having a single JFET with low feedback and a transformer output. Which one is the better sounding circuit, I cannot tell and I guess will depend on personal taste, source material etc.

I plan on using this mic for experiments with the circuit as is and compare with ORS87 and a transformer output circuit that I designed myself. Just for fun and learning.

Jan

Yes, it is more linear and has less coloring than U87, but it has more coloring than the Schoeps circuit.