MY MIC MT2 Aoshen M3 microphone

[LevinGuitar]

https://www.alibaba.com/product-det...odcasting-computer-singing-1600280735798.html

Bought on local market for fun. The body feels heavy and solid but the upper part don't sits perfectly on the lower one when screws are tighten. The lower part rings when dissasembled but in the assembly seems to be ok. Two layers mesh, good capsule (the flatter one?) The circuit seems similar to the BM800 but with 20nf RF caps and not sure if really the same bias arrangement.

 

[LevinGuitar]

This mic have no noise issue, high output. Awesome for the price!
I wonder if I can use the stock fet K596 with schoeps topology for the source, but without feeding the gate with specific voltage (as it already have a resistor and diode integrated). And after that use the source as the signal for the phase splitter, as the B2pro does. That should lower the output and maybe distortion?

 

[RuudNL]

Personally I don't see the point of adding an extra transistor after the FET.
Drain/source impedances are low enough to directly drive the output transistors.
Impedance at the base of the output transistors is (Hfe x Re) // 150K.

 

[k brown]

Capsule appears to be "KK12' V1 ('the brighter one').

https://groupdiy.com/threads/the-mi...-information-thread.88240/page-6#post-1162461

 

[LevinGuitar]

Well, I tried my idea, but have no signal. Seems the Q5 isn,t working with this bias

 

[micolas]

Personally I don't see the point of adding an extra transistor after the FET.
Drain/source impedances are low enough to directly drive the output transistors.
Impedance at the base of the output transistors is (Hfe x Re) // 150K.

@LevinGuitar
I agree with @RuudNL
What do you hope the Q5 will give you in addition to a classic Shoeps?
Anything you add to the audio chain will affect noise, distortion, etc etc

 

[LevinGuitar]

I wanted to try both and see the differences. Ruud,s suggestion works nice

 

[micolas]

I wanted to try both and see the differences. Ruud,s suggestion works nice

To be honest, I have also done this many times. Sometimes successfully, sometimes not.
It's in our nature to be curious, to try all kinds of options.
In fact, this is the DIY spirit.
I watch you enthusiastically try all kinds of things. This is the way to progress

 

[LevinGuitar]

For now I kept the original 10K resistors and tried the @kingkorg NT1Black RLC filter mod, adjusting the Q factor resistor to 25K. I guess if I lower the 10k to his original 500R specs, a 1.8K in the RLC would work similar and with lower noise?

This 20$ mic now sound super pro!

BTW the metalwork of the body and screws are good, the only really bad quality parts here are the capsule cables

 

[micolas]

For now I kept the original 10K resistors and tried the @kingkorg NT1Black RLC filter mod, adjusting the Q factor resistor to 25K. I guess if I lower the 10k to his original 500R specs, a 1.8K in the RLC would work similar and with lower noise?

This 20$ mic now sound super pro!

BTW the metalwork of the body and screws are good, the only really bad quality parts here are the capsule cables

Can you put a schematic with these changes?

 

[LevinGuitar]

I guess the filter can be a bit better adjusted to this particular capsule and headbasket still

 

[k brown]

For now I kept the original 10K resistors and tried the @kingkorg NT1Black RLC filter mod, adjusting the Q factor resistor to 25K. I guess if I lower the 10k to his original 500R specs, a 1.8K in the RLC would work similar and with lower noise?

This 20$ mic now sound super pro!

BTW the metalwork of the body and screws are good, the only really bad quality parts here are the capsule cable

For a less bright capsule:
https://www.jlielectronics.com/microphone-capsules/jli-3410au/

 

[micolas]

For now I kept the original 10K resistors and tried the @kingkorg NT1Black RLC filter mod, adjusting the Q factor resistor to 25K. I guess if I lower the 10k to his original 500R specs, a 1.8K in the RLC would work similar and with lower noise?

This 20$ mic now sound super pro!

I guess the filter can be a bit better adjusted to this particular capsule and headbasket still

Yes, it seems to be a slightly wider notch filter, with a small Q value. What frequency is it centered at? (where does the capsule/headbasket have the ~ maximum treble boost?) You probably tried to get as flat a response as possible for the microphone.

 

[LevinGuitar]

With that 10k resistors the filter becomes more eficcient? so the Q factor isn't that small. I started with 1.8K and it was a sumbarine sound

The original combination is centered about 10-11K.
My 20hH inductor resulted to be a 24mH when measured

 

[LevinGuitar]

I lowered the 10k resistors and, as everyone said here, the noise decrease. I'm using 220R for now.

The R in the RLC filter also comes to the original 1.8k value as a good starting point.

 

[micolas]

@LevinGuitar

Why don't you use a deemphasis circuit (like NFB at U87) instead of this notch filter? THD, noise, etc. will improve.

 

[LevinGuitar]

Well, I like this flatter mods. Also with schoeps circuit that deemphasis is not so efficient. Have to try mix them both. Without the 10k resistors, the S/N ratio is very similar to the NT1black...

 

[micolas]

Well, I like this flatter mods. Also with schoeps circuit that deemphasis is not so efficient. Have to try mix them both. Without the 10k resistors, the S/N ratio is very similar to the NT1black...

I doubt the noise of this circuit is similar to that of the RODE NT1 Black.
What jFET did you use?
***
I mean the deemphasis circuit exposed by @RuudNL , the capacitor C4 gives you the attenuation that satisfies you.

 

[LevinGuitar]

I have used that idea in the B2pro mics and it wasn't enough (went up to nf range deemphasis caps). The HF attenuation became nice when combined with a capacitor from source to drain, but the noise increased a bit.

I'm using the stock K596 fet. The s/n gain of the original circuit is even lower. But after the Schoeps mod is still super quiet with a lot of gain.

Have no idea why this stock circuit have no usual noise issue from the zener btw