Amp/Preamp Asylum - Ming Da MC-2A3 preamp schematic - jwu - snoopy.org

Just want to share with fellow audiophiles a schematic of the Ming Da MC-2A3 preamp.

Interesting topology:
2A3 rectification, EL34 + 6SN7 regulation of B+ (in=400V out = 220V, very strange), somewhat unsophisticated filament power supply with filaments wired in SERIES, 6SN7 in SRPP mode with 6922 follower
(one 6922 as constant current source).

The unit that I got as well as the units depicted in the picture
http://www.pacificvalve.us/images/MC_2A3_Inside.JPG
and here:
http://www.audiocostruzioni.com/r_s/pre/ming-da-mc-2a3/mc-2a3.htm
do not show the 5.1kOhm resistor on the B+ rail separating the 6SN7 stage
and the 6922 follower stage.
This is BAD and not only will the resulting B+ to the 6SN7 be too high, it could even result in coupling between the 2 anodes causing oscillations.

My unit has the green 300Ohm resistor but the unit depicted here
http://www.audiocostruzioni.com/r_s/pre/ming-da-mc-2a3/dentro.jpg
does not have that resistor which separates the regulated B+ from the main anode rail.
Also my unit has SCR MKP caps vs. the Mundorf MCap / Sprague gum drops.
That tells you how consistent these Chinese manufacturers are when it comes to components.

The description of the preamp @ the manufacturer's website sucks.
There has not been a review of this unit on the several major audio-rags
or sites like 6moons or enjoythemusic.
The unit looks somewhat of a monstrosity.

I got a super deal on the preamp, and must admit I bought it for curiosity with no high expectations whatsoever,
and I was stunned by its sound. In my system, stuff like Audio Research Ref 1,
Cary SLP98P, Canary CA801SE dont even come close.

Ming Da did a not-so-good job voicing the MC-7R ( noisy, hot, aggressive, colored, but can be fixed with some mods ). They did it right this time (at least thats the way it is in my system).

Last but not least thanks a lot to the fellow AudioAsylum member who graciously shared with me the schematics, I will commence doing some mods by replacing some components with the known premium ones and see how far I can improve it.