• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Ming Da MC-3008-A2 Mono Blocks

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#44
Legis said:
I recently bought the 2012 version of the amps (stainless steel chassis, not aluminum). I like them. The amps feels solid and sounds very good with stock tubes and without any mods. 300B + 805/FU5 is very musical and dynamic combination.

The amps were packed good and the bigger tubes and the tube covers came in a separate box.

I received FU-5 + Jinvina 300B tubes. There was no information regarding the 12AX7/12AU7 tubes which way they should inserted (which one goes to left/right socket), at least in a language I understand.

The polymer capacitors inside are mainly Jinvina brand also, which is Mingda's own brand.

Mingda also makes the OPT's (and power transformers) they use. I read somewhere the core material is advertised to be imported from Japan.

The power transformer is relatively quiet but not totally silent in my electricity line. It might be partially potted since I could not remove the cover. It's top also sounds "full" when I knock it, but the sides do not, which might hint that the trafo is partially potted. If one wishes one could fully pot it by pouring in more epoxy from the hole where the wires go inside the amp. I'm considering it, I cannot remove the cover anyway so no harm potting it fully. By the way, what do you guys think about using "basic" (normally thermally conductive, not super conductive) epoxy in potting, does it raise the power transformers temperature compared to partial potting? Or lower it?

The OPT's cover was not just for the looks, the OPT is an almost tight fit inside the cover! It's core's dimensions are (W*H*D) 11,5*10*7cm, quite a big fella. The windings are impregnated and the core/everything is wholly covered in an epoxy layer. It feels very solid and heavy. The amp is quite back-heavy when you lift it since propably 70-80% of the ~25kg mass (have not measured) comes from the transformers. 🙂

Some cap mods are propably coming at some point in the most critical spots. I might bypass the global negative feedback loop also or put it behind a switch. I'm interested to hear how they sound then based on Lampizator's comments. I feel the base is very good to do slight modding. Point to point layout is superb, easy to change components.

edit. The amp also supports the non-capped 805 tubes also as stock. The "pearl string" is connected directly to the tube socket pin.

Some pictures:
Click to expand...

Hey there im so sad that i can not see your pictures in this tread.. i have just got the mingda mc3008A monoblocks brand new. and the upgrades you have made is something i would like to do to mine. i will post som pictures in this tread if its okay?
 
#45
Hi folks.
One monoblock stopped playing yesterday. I can hear that the relay do not click-in and the B+ is dead. All other voltage is correct.
Is that the trafo-windings for B+ or is it the relay...?
The shcematics do not show how the relay is fitted into the circuit.
Help...!
🙂
 
#46
The Cary Interstage transformer, in Post # 33, that has parallel caps from primary to secondary . . .

I suspect that is to make up for the high frequency rolloff of the interstage from primary to secondary
(the IT leakage reactance from primary to secondary is too high).
Just a 'simple fix".

Is the total result of Interstage Transformer and Capacitors good?
Your guess is as good as mine.
 
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