Audio M 6000 E

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Full review in AUDIO magazine (Germany), Issue May 2008

Accuphase Monophonic Power Amplifier M-6000

On The Safe Side by Malte Ruhnke

Nothing was left to chance: the mono blocks M-6000 are going to set a new benchmark in the portfolio of Accuphase. And they've got the making to bewitch even the most discriminating listeners.
Giants, a reason for celebration, the best power amps of all times - with superlatives like these AUDIO was welcoming Accuphase's monophonic amplifiers M-8000 in the year 2002. With all due respect, where and how can this renowned manufacturer top these amps by launching the M-6000 now in 2008? Actually, I always thought that progresses in amplifier technology could have been only marginal in the past six years while the top dogs up to now are surpassed by the newcomers neither by their sheer size nor by power specs.
Well, the virtues of these Japanese power plants simply cannot be debated even by down-to-earth contemporaries: their stability under any condition guarantees that even with critical, demanding speaker systems the sonic results are not spoiled by interactions between amp and speakers. The overwhelming output power will bring also low-efficiency transducers out of their shell. Month by month the newest hifi appliances are introducing themselves in the AUDIO listening room and hence for comparison purposes a power amplifier, which is stable under any conditions, is worth its weight in gold.
DA CAPO
Talking about value - this seems to be the biggest difference between a pair of
M-8000 and M-6000, whereby the latter, with nearly the same promising power,
comes with a price tag which is about 35% less expensive than the one of its bigger brothers. No question, this is still a lot of money for two monophonic power amps, yet,
like with any other audio component from Accuphase, when put into perspective as to the stable value over the time and outstanding workmanship, one might think a bit different here.
Very few changes can be noticed when the M-6000 is viewed from the outside.
Except for some prominent features on the front panel, which in the M-8000 are decently hidden, namely the switchable input sensitivity, absolute phase and a selector switch for balanced or unbalanced inputs.
PRELUDE WITH TECHNOLOGY
Inside, however, we are to encounter some big changes indeed. Instead of bipolar transistors there are field-effect semi-conductors, a.k.a. MOSFETs, taking care of the final amplification. While conventional solid-state devices of the bipolar variety are trying to amplify low base currents, the work of MOSFETs can be compared with a tunnel for electrons of which width and thus flow rate is regulated by an electric field.

Rather, the function principles are reminding us of those going on in a thermionic valve, and this is also why many high-enders believe the sound of MOSFETs coming close to the sound of valves.
Instead of employing a pure Class-A circuitry, in which the power transistors are permanently wasting half of the maximum output power in form of heat,
Accuphase has gone for a push-pull circuitry in A/B mode of operation in the two big mono blocks. An array of 16 MOSFETs amplifies the signals below the cross-over