Hi, first time posting here.  My name is tong and I am a us army veteran of 6 years, 2 combat tours, avionics commo tech so working on audio circuitry was and is a big part of my life.  I make mostly synthwave vaporwave type beats and i am in the process of learning to sing and play piano.  I go by the name of play.exe on itunes/spotify/youtube etc.  if you're curious about my music :)

issue:
I bought a mp-v57 from mic-parts, i have the pcb fully assembled, but i am having self noise issues.  I am using a mic body from a mxl v63m, and the stock capsule it came with until my k67 clone capsule comes in from china.  I have made polarization circuit adjustments to 60v.  Has anyone had any  experience with these kits?  It was a fun project but i  would like to maximize clarity and low self noise while maintaining excellent sensitivity.  I am going for a u87ai sound, I ordered a k67 double sided clone capsule, but right now am using the stock v63m single sided k67 clone capsule. 



RuudNL

First eliminate the source of the noise.
Is the noise still present if you remove the capsule and connect a ~68pF capacitor to the input? (Gate of the FET)
If the noise gets lower or disappears, you know it is caused by the capsule.
Did you clean all high impedance parts and remove flux residues?
Even a fingerprint on a high value resistor can cause increased self noise.

By the way: as far as I know, the V57 does not include any frequency correction.
With a K67 capsule this might result in an overbright microphone.
« Last Edit: July 22, 2019, 05:37:12 AM by RuudNL »
There is a solution for every problem!

http://www.vansteenisaudio.nl

First eliminate the source of the noise.
Is the noise still present if you remove the capsule and connect a ~68pF capacitor to the input? (Gate of the FET)
If the noise gets lower or disappears, you know it is caused by the capsule.
Did you clean all high impednce parts and remove flux residues?
Even a fingerprint on a high value resistor can cause increased self noise.

By the way: as far as I know, the V57 does not include any frequency correction.
With a K67 capsule this might result in an overbright microphone.

Excellent suggestions RuudNL!  I chose a linear circuit, and the k67 to try and get the same bright sound as the u87ai / tlm103.  The circuit kit does come with different capacitors for high frequency attenuation.  Maybe they updated the kit?  There are 3 or 4 different configuration choices, linear / small attenuation / medium / large attenuation in the high frequency range.  I chose linear, but the kit supplies all the necessary caps should I decide later its too bright when my new capsule gets in. 

I took your suggestion and did a thorough alcohol bath on the whole circuit with a dental tool and a magnifying glass, followed up with cotton swabs and a fine needle nose pluckers to pick up the fibers.  There was alot of solder residue underneath resistors and the high impedance section of the circuit that I did not see without the magnifying glass.  Thank you for that suggestion, so far testing has been excellent.  The mic is quiet, and the sensitivity is still superb. 

Pretty amazing what the flux can do...good job on your first build! Stick around here and you’ll be busy for years.

You can socket those caps to be able to easily fine tune your freq response

—Mark


 

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