MING-DA MC805 SINGLE ENDED CLASS A VALVE AMPLIFIER
Da truth
The Ming Da MC805-A Single-Ended valve amplifier delivers a truthful sound, Noel Keywood finds.
If there’s an amplifier that is mythically perfect, it is the Single-Ended, or SE. In real life they are anything but perfect, but most people acknowledge that sound quality wise, they are unbeatable. I wouldn’t say an SE shades all else, but they are always delightfully solid sounding, putting more meat on the bone it always seems to me, than your everyday push-pull types. And here to demonstrate and prove the point are a pair of Ming Da MC805-A monoblock Single-Ended power amplifiers. Feeding them in this review was an updated MC 300-PRE preamp, tweaked by the UK importers to eliminate the problems I experienced with it (see our September 2011 issue).
By definition Single-Ended amplifiers lack crossover distortion, but to be truthful they don’t lack distortion, so their notional perfection is just that. The reality is a little different from the rosy picture some paint of the SE, but at the same time I have yet to hear a bad one. In spite of the difficulties of their design most SEs are valve amplifiers. Few transistor Single-Ended amplifiers exist, because audio transistors run burning hot in this role, but in the UK Tellurium Q and Sugden make them. Valve amplifiers need gapped output transformers able to withstand direct-current passing through them without suffering magnetic saturation (overload). And they need massive cores as well, making valve SE amplifiers very heavy, unless power output is limited. So as you might guess most SEs are low power amplifiers, in order to make them liftable, and they are usually monoblocks too, just to make them physically manageable. And that describes in outline the Ming Da MC805-A monoblock power amplifiers reviewed here. Each one weighs 22kgs, heavy but liftable, and measures 230mm wide, 480mm deep and 240 high, at least with 805s lacking top caps as fitted to our amplifiers. Power output is quoted as 40 Watts but ours produced way below under test (see MEASURED PERFORMANCE). It sounds little, but in use the meters showed that, as usual, very little power is used in normal daily use and I never got the meters near their red overload zone.
Each amplifier uses a single 805 power triode, two 6SN7 small signal triodes and a Chinese 6P3P (6L6) acting as a driver. Our amps had ‘different’ valves to those shown on the UK website or on the web generally. This is because there are numerous variants of the 6L6 and 6SN7, both in shape and designation and the UK importers prefer the standard tubular 6SN7 to the 'Onion bulb' variant, that may look good but is microphonic. You will even see 805s with anode top caps being used, but since the cap is probably carrying 800V or so, you will not find such a tube being used in any country with safety laws!
The rear panel carries an 8 Ohm output with a 4 Ohm tap, plus a single phono input socket. Mains power is switched on by a rocker switch lurking on each left side, just behind the front panel. Power amplifier switch-on was fuss free; there was no thrum from the transformers nor any switch on thump. Like most valve amps these run up slowly and smoothly, the big 805s emitting a bright glow from their thoriated tungsten heaters.
Feeding the monoblocks was the aurally impressive MC-300 preamplifier. Ming Da UK have eliminated the bass peak I found under review by changing feedback capacitor values, and cured excessive microphony by fitting non-microphonic 6SN7 valves. The MC300-PRE has balanced inputs and I fed it from the balanced outputs of our Electrocompaniet ECD1 DAC. Outputs are unbalanced phono sockets that feed the power amplifiers.
SOUND QUALITY
The MC805-As were, not unsurprisingly, as sweet and pure in their treble as you could either imagine or hope for. To say they had liquid treble would barely do them justice. It is only when you hear cymbals ringing with such sonorous purity that the justification of amplifiers like this becomes apparent. If valve amplifiers produce treble that is easier and more convincing in its timbral character than transistor amplifiers, then SEs like the MC805-As take the whole process a step further, with a quality rarely encountered elsewhere. These are amplifiers that charm your ears, not chew them. As you might expect there is no sign of top end brightness or harshness, but at the same time these amplifiers reach 38kHz and there is not the slight sense of warmth that comes from a roll off above 15kHz or so caused by the distributed capacitance in the giant winding stacks of high power output transformers.
A deliciously lucid yet fast midband quality had Renee Fleming singing clearly just in front of the loudspeakers with a tactile presence that only valve amplifiers can manage. The amplifiers also painted up a gloriously wide sound stage on which instruments and singers had a rich and intense presence, even at full left and right. I recognised this as a property of the MC300 preamplifier, a highly specialised design tuned right up to the limit using specialised valves and components. Like all Single-Ended amplifiers the MC805-As gave a big, solid feel to singers and instruments, placing them onto a sound stage that fell away backwards, giving a feeling of great depth.
With low damping factor valve amplifiers like these, bass quality depends much upon the acoustic and magnetic damping in the loudspeaker I have found. I used the MC805-As across a wide variety of loudspeakers, including World Audio Design KLS9s, Spendor S8es, Tannoy DC8Ts and Linn Aktivs. They gave strong, well controlled bass with all these loudspeakers except the Spendors, which are under-damped and boom with valve amplifiers. Valve amplifiers generally sound fuller bodied than transistor amplifiers, but the MC805-As took this a stage further and could thunder when volume was turned right up.
CONCLUSION
Providing suitable loudspeakers are used there’s little can better a Single-Ended amplifier like the Ming-Da MC805-A. It has big, full bodied sound that comes across as lithe but tactile as well. Yet this amplifier is so naturally pure and sweet in its treble it is unmatchable by all else except other valve SEs. The glorious MC-300 preamplifier is a must and it raises the price of the package of course, but less will not do. It contributes strongly to wonderful sound staging, bringing a vibrancy to instruments unmatched elsewhere. This is a great combination of pre and power amplifiers, one that gives the highest sound quality. Obviously, the output transformers need optimising to deliver close to the quoted power. This apart, the Ming Da amplifier combo is recommended, because it gives breathtaking sound quality from an easy to use package that is fuss free, yet convincingly thermionic high-end.
Fabulous Single-Ended sound with no drawbacks, except less power than quoted. Need careful loudspeaker matching.
FOR
- sweet treble
- broad, intense imaging
- big bodied sound
AGAINST
- small speakers don’t suit
- less power than quoted
- size / weight
Ming Da MC805-A £3499/pr
Ming Da
+44 (0)1684 293111
www.mingda.co.uk
MEASURED PERFORMANCE
The Ming Da MC805-A produced 14 Watts for 1% distortion and 20 Watts for 3%. The quoted output power of 40 Watts was only approached by putting an 8 Ohm load on the 4 Ohm tap, where 36 Watts was achieved for 3% distortion. This indicates the secondary is incorrectly load matched and needs fewer turns.
Overload was slow, as usual with single-ended valve amplifiers having limited feedback. Full output was delivered at 40Hz, distortion measuring 2% at 14 Watts, mostly third harmonic from the transformer.
The meters indicated full output at a 3% distortion level and were accurate enough in showing a realistic overload level for musical peaks. When power is limited meters like this are a good idea I feel.
Distortion levels were low in the midband and comprised second and third harmonic at lower power levels. Higher harmonics appeared as power increased though, and this is usually due to the output transformer core moving into saturation, a big issue with single-ended valve amps and the reason they have massive transformers. High frequency extension was good from these transformers, considering their size: they reached 38kHz -1dB.
Damping factor was inevitably low, measuring just 3, so a loudspeaker with good acoustic damping is needed, like a Triangle Antal or similar. Sensitivity was normal enough at 0.76V for full output (i.e. 14 Watts). Noise was low at -90dB and hum a low 1.5mV at 100Hz, just audible close to a loudspeaker.
The Ming Da MC805-A needs better output load matching to achieve its quoted power output and achieve its full potential. However, with an 8 Ohm load on the 4 Ohm tap it worked properly and gave a decent set of results. NK
Power 14watts
Frequency response 2.5Hz-38kHz
Noise -90dB
Distortion 0.23%
Sensitivity 760mV
Damping factor 3.1
