Microphone Parts MP-V57 schematic?

I'm interested in modding an MCA SP-1 with one of Microphone Parts' U87-style capsules, but the price on their PCB replacement kit -  $130  for the MP-V57 boards (plus components) - seems pretty steep for what it is.  Does anyone have a copy of the schematic so I can translate it to vero or perf (or Eagle)? Or have perspective on the MP-V57's original circuit inspiration? Also: How far into MP's vaunted "Neumann-esque" territory would I get by just swapping caps/doing common mods?  I don't necessarily need to turn this mic into a multi-pattern thing, as my main aim is to improve my vocals/guitars/room mic arsenal; I just want to get into "high end" cardioid LDC territory and complement the capsule with an appropriate circuit and electronics.

I doubt that there someone will share with that circuit, but out of curiosity i'll be happy to see what are the "improvements"
For MCA you can make huge improvements like with MXL 990 (same circuit).
I have great results with K47 copy and I recommend you to use it instead k67/k87.
You don't have to buy microphone parts version, there are also cheaper and great capsules available.
No need to filtering high frequencies. Also reversed polarization gives better performance and if the mesh is three leyer, remove one.

This is all useful - I sometimes get into a mindset where I obsess over one option, and people seem to rave over these Microphone Parts kits.  Do you have any suggestions in terms of alternative capsules?  And, if a 47-style capsule works best in a MCA SP-1 mod, what is the quickest/cheapest route towards a somewhat reasonable U87-style mic?  I'd like to have reasonable variations on (if not perfect clones of) both mics in my locker at some point.

Check PM

For what I know after speaking with them, is that it's a KInda Schoepps design with some modifications in it. Can't tell you about the mods, thought. But you could work along the Schoepps circuit and play with it to find what suit you best

For me it looks like typical schoeps with added pattern selection - something like Jim NT2 design (if it's not the same design).

http://3.bp.blogspot.com/-LHFEhbsE878/VDyuMvdAZYI/AAAAAAAAAV0/MJOdA9T2z8Y/s1600/Trenton-Blizzard-Mic-Kit-PCB-1-2014.jpg

http://cdn.shopify.com/s/files/1/0867/8438/products/v57a.jpg?v=1432495986

I don't see any new improvements like effective high frequency damping for k67 etc.

Actually, I don't know if he integrated the corrective section for K67 capsules. They provide their U87 capsule with their microphone kit, so I guess they integrated some sort of corrective EQ in it.

I don't see in the picture any other additional capacitor than it is in basic schoeps circuit, so am guessing there's no additional correction.
The only hf correction is standard like in schoeps circuit (on the picture are two 470pf caps) .
NT2 had K67 also in same way.

it's possible. we could ask Microphone parts, too

Naaah... i prefer speculations

ln76d said:

Naaah... i prefer speculations

Click to expand...

haha.

You can do a HF rolloff (for a K87) by connecting a capacitor in parallel with the drain resistor of the FET.
(This is also the principle the mparts is using.)
Not exactly the correction a K87 needs, but you can get close.

RuudNL said:

You can do a HF rolloff (for a K87) by connecting a capacitor in parallel with the drain resistor of the FET.
(This is also the principle the mparts is using.)
Not exactly the correction a K87 needs, but you can get close.

Click to expand...

Hi Ruud!

It looks like it unbalancing output a little bit, am i right?
Why not to put capacitor at the drain and another at the source? Quick simulation shows nice response.
In case V57 circuit, there's no additional option for drain capacitor on the PCB.

With a capacitor between the source and drain, the frequency response looks good, but this circuit will give more distortion.
And concerning the 'unbalancing': the only thing that counts is the voltage (difference) between pin 2 and 3 of the XLR.
Because the FET is buffered by two PNP transistors, the output impedance on both pins will still remain the same.
Disadvantage is that the maximum attenuation for high frequencies can (theoretically) be 6 dB.
(This R/C on the drain principle is advertised by mparts as 'corrective EQ')

Here is an example of different values in parallel with R.drain:

Could you post the values of capacitors corresponding to curves on the chart?
I could test it right now, cause i'm working currently on schoeps style -  circuit microphone

Ruud? Where are you?

This is what i get on pins in simulation  - 15nf paralell to the drain resistor.
Is it possible that on the second pin hf increased?
Does it affect somehow to the fet biasing?
15nF sound pretty good in the circuit.

For the examples I used a so called BCD switch, with 2.2 nF, 4.7 nF, 10 nF and 22 nF.
This way I could get multiple combinations.
So what you get is:

0 : No capacitor
1: 2.2 nF
2: 4.7 nF
3: 6.9 nF (2.2 + 4.7)
4: 10 nF
5 12.2 nF (2.2 + 10)
6: 14.7 nF (4.7 + 10)
7: 16.9 nF (2.2 + 4.7 + 10)
8: 22 nF
9: 24.2 nF (2.2 + 22)

A capacitor in parallel with the drain resistor attenuates the high frequencies, a capacitor in parallel with the source resistor boosts the high frequencies, but we don't want that!

Only AC is affected by the capacitor, so it does by no means change the FET bias.

(By the way: I am not Ruude and certainly not Rude! My name is Ruud, that is short for Rudolph (No, not the red nosed reindeer... )

RuudNL said:

(By the way: I am not Ruude and certainly not Rude! My name is Ruud, that is short for Rudolph (No, not the red nosed reindeer... )

Click to expand...

Sh.. I'm really sorry for "Ruude"  ;D  ;D  ;D
I don't know how or why i wrote it worng... 
In previous post was ok
Let's say i was sleepy
I figured out a some time ago that is short for Rudolph

Thank you very much for the values of the caps from the chart!
Right now i have 15nF installed and tommorow i will test 22nF.
It sounds pretty good with 34mm k67.
Btw. on my chart hf rise on one leg with capacitor on drain resistor only.