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MC833-A MONO BLOCK POWER AMPLIFIERS

Specification:

output power:90W (Class A)
output impedance: 4Ω, 8Ω
input impedance:220K
input voltage:1000mv
distortion:≦1%
signal to noise ratio: 94dB
inputs: 1 pair of balance input , 1 pair of unbalance input
outputs:2 pairs
power consumption:400W
frequency response: 18Hz~26KHz+/-1 dB
valves:FU33 x1, Psvane 300B x1, Tungsol 6SL7*1
net weight for one channel: 53KG

Net size: W x D x H= 40 x 59 * 55 (cm)

 

 

 

 

 

 

 

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Review translation of MC833-A in the Chinese audio magazine Avfline:

Meixing (Mingda) already began to develop their powerful valve amplifiers some years ago to challenge the pinnacle of vacuum tube amplification. They have launched some huge valve amps with unusual and big vacuum tubes. Audiophiles and audio magazines have been deeply impressed by its flagship series. The magnificent design with accordance of fantastic sound are the hallmark of Mingda. Though Mingda has great achievements in grand valve amps, it still keeps on producing its middle and small size amps so that customers can still enjoy its classical products.

We can say that Mingda has strong capability in design and development in the field of valve amps. Recently, this outstanding manufacturer introduced us some of other new grand valve amps which include MC3008-AR integrated with power amp, MC845-CS integrated with power amp, MC212-A mono blocks power amps, and MC833-A mono block power amps. What’s more, one of new products is Bluetooth receiver valve pre-amp, the MC BT-66.

I got the chance to hear these new valve amps in Guangzhou AV show in June. The owner of the factory Mr. Xiao introduced me to these new amps in great detail, especially MC833-A mono block power amps. After acknowledging these power amps and experiencing the power of the mono's, I would like to share it with the readers here.

 

The power: Class A single ended 90W

Mr. Xiao, explained to me that the MC833-A has an output power 90W in Class A Single ended! Class A valve amps are outstanding performers in the field of amplifiers, particularly in valve amps. 90W Class A is an output power that is definitely powerful for valve amps. For the users, Class A circuitry is the pinnacle of perfection to users that you can’t ignore. The circuitry is without crossover distortion and runs at the maximum current levels of power dissipation, to provide the most gorgeous sound for listeners. The density and cohesiveness of the sound are far better as a result. ?

The vacuum tubes: FU33 as leading part, 300B as an accompaniment

There is a rule that Mingda use to name the models for their products, for example, MC833-A, the A refers to the Class A circuitry and the MC833 implies the name of the output power tubes for the amp. So MC833-A must use an extraordinary power tube to support the 90W output power which is the called FU33 or 833, (here we say FU33).

But FU33 is not a new tube developed in the last few years, nor there is replica ?available in the market. So then where and how did Mingda get these tubes?
Mr. Xiao told me that there were valve factories in the late 1960's that produced these powerful triode tubes for audio use and he bought them in large quantity when Mr. Xiao heard that there are still new and old stock. Compared to the tubes in the market, these NOS can have a better guarantee of lifespan, not only that, Mingda also burn in the ?tubes with more than 50 hours before carefully selected which ones are used on MC833-A.

According to Mr. Xiao, FU33 is a powerful triode tube with high anode voltages. Indeed, specification of FU33 is astonishing, such as its maximum anode voltage can reach more than a thousand volts and the maximum anode power dissipation can be up to 300W. Its heater current is 10A which all requires huge?capability from power supply. So we can see that it is not easy to design using the FU33, then why does Mingda go through the challenge to make an amp with this tube? Mr. Xiao told us that this tube can stand high voltages with nice sound and the sound stage large and vivid, the Class A output power is dynamic and effortlessly performs music!

There are quite a lot of Mingda amps that use 300B as driver tubes, including the MC833-A. Audiophiles know that valve amps sound brilliant with 300B and as output valves these tubes can always produce elegant and charming sound. However, it also has the disadvantage that the output power is relatively low, mainly lower than 10W, which will not be capable of driving some speakers with low sensitivity. The 300B has been designed in the circuit to directly drive the FU33 in this amp because it can reproduce the natural mellow sound of the 300B, but then with higher output power so that the sound has superior dynamics. The other reason is that FU33 uses the 300B, is that the FU33 requires driving with a lot of power, so 300B driving is a perfect tube in this circuity. The input for this amp is 6SL7 which is a tube with both power and strong amplification, giving this amplifier great sensitivity and dynamics.

 

Potentiometers setting: With XLR input

Aside from the RCA input, MC833-A is also designed with XLR input. In fact all of the flagship amps from Mingda are with XLR/balance inputs: it is unusual, but the balanced input is provided by valves which is quite rare in amplifiers. Regarding the outputs, there are 4Ω and 8Ω binding posts for the different speakers.

There are a pair of potentiometers located on the side of MC833-A which allow both bias setting on BIAS ADJ and hum reduction on HUM ADJ. After these power amps have been used for some while, or if you would like to replace new tubes, it is necessary to bias the amps again to make the amps work in the best conditions. Therefore the potentiometers and meter connections make this very simple.

Two Questions:

Reliability: Audiophiles are particular about the warming up time for valve amps. People who know Mingda will find that Mingda prefer to warm up the amps without any loading, ?without any pre-amp input and speaker output, which is quite a complex circuit design, so I do not recommend readers to try to do this. Usually power supplies with high voltage can provide large power and dynamics, if not designed properly it could create some instability. However, the Mingda amplifiers in the show were working for the whole day without being turned off for a second which is a big challenge for amps with high voltage. We can see from this that Mingda amplifiers are extremely reliable and stable.

Warming-up:All audiophiles have common sense that amplifiers should be warmed up and it takes longer time for valve amplifiers to warm up rather than solid state amps. Some users may prefer to warm up the valve amps with one hour, but Mr. Xiao said that 20 minutes for warming up is enough.

Sound testing:?
The showroom is with the area of about 20 square meters which is not a big room for valve amplifiers with 90W. Mingda uses its MC300-PSE pre-amplifier to drive the MC833-A mono blocks running with Tannoy Turnberry GR floor?standing speakers. Sensitivity for the speakers is high and seems there is no risk for the MC833-A. I would like to share with you the performance of MC833-A here.

The MC833-A is indeed has great driving power and dynamics. Under the driving of 90W Class A, the sound stage is wide and easily fills the room. There is impact force when it comes to big dynamics, such as when you listen to the track ROUND UP. It was so vivid and large that you feel you are on the stage, you do not feel that the performance coke from two speakers. MC833-A is even better than its predecessor like Mingda MC80-AS mono blocks, or the new MC3008-AR integrated amplifier, because the sheer power output of MC833-A grabs the advantage.


You can hear that the MC833-A is open and straight when performing, without compromise. When playing music with big dynamics, the bass is very strong and firm and transparent, the mid-frequency is wide and deep, the treble is penetrating and you can describe the sound with the word as “imposing”. Any track that plays through MC833-A does not lack bass as its bass is deep to the bottom registers and I feel that 20 square meters is far from enough for MC833-A to show its capability, unless we turn the volume down!


The mid-frequency is usually the soul of music. You hear the nature of the sound if it is without the mid-range. Take the Saxophone for example, if there is not enough mid body, then the sound of the Saxophone can be very thin and sharp without the rounded and soft sounds. However, this MC833-A can create the roundness and softness with plenty of mid-range. Without exception with strings, the violin is tender, warm and with emotion. Sound from our Chinese instrument Pipa is clear and transparent, full and nature.

The sound of MC833-A is imposing, so does it mean that it could be too forceful and without soft control when it comes to the track that should be smooth and delicate? Obviously not, on the contrary, you can hear the depth and warmth oozing from it. We can hear the violin in the Unforgettable Dream by Ruowen is filled with the aroma of pine and you can hear every detail of the vocals.
Overall, the sound stage of MC833-A is not plain. Its sound is full and?natural with excellent dynamics. You can feel its width and deep background especially when the track comes to the large music imaging.

Summary:
The experience of developing large power output amps makes Mingda products to be more mature. Just like MC833-A Class A single ended, the driving power and the dynamics are far more than just better. The sound is appealing with large background and dimensional which also present the reliability, stability and elegance of Mingda flagship amps. It just fit in exactly an audiophile's wish, when they like the sound to be imposing and powerful.

 

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The review in Chinese audio magazine Avfline:

 




 
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