Review in AUDIO magazine (Germany), August 2004
Accuphase Class-A Power Amplifier A-60
Up please!
by Joachim Pfeiffer
Since generations amps from Accuphase have always remained true to their visual appearance and from a sonic point of view have become better and better over the time,
though, to this date, in small steps only. What follows now is a quantum leap.
Why a power amp like the new A-60 from Accuphase? Let's ask someone who should know, namely AUDIO's speaker tester Knut Isberner. It's because hardly anyone else could gain as much experience with the predecessor model A-50V from the same maker. For him the "50V" is simply the best choice when it comes to driving his own, highly critical Infinity
Kappa-9 speakers (yes, I do mean those aged amp-killers &). The efficiency of the "9" is certainly not a good one, yet in some way acceptable. What makes the Kappa the enemy of nearly all amplifiers is their impedance curve in the so-called "extended position" which has always been preferred by my colleague. In this position the speaker impedance drops way down to the extreme value of around 0.78 Ohm in the ultra-critical bass region.
For this reason any power amplifier that is to be hooked up to the Kappa should be able to provide an ultra-stable, perfect voltage-impedance cube (see lab report on page 128)
without any sign of collapsing at whatever spot. Otherwise the speaker divas are going crazy while quite a few of those little amps are waving "good-bye" and, in the worst case, go up in smoke. It's not really sensational that the A-50V is driving this Infinity-legend without flaws.
Other amps with a similar price tag can do that also - and quite laid-back nevertheless. What made the A-50V so fascinating to Knut Isberner was not what it was capable of doing, but how it eventually performed. Smooth, consistent and with an unusual differentiated rendition of sonic colours did this combination conquer Isberner's listening room and thus his audiophile heart as well. This may well be due to the fact that the A-50V, its predecessor
A-50 and now the successor A-60 sweat away in Class-A mode of operation.
Big power meaning lots of glory?
This mode is certainly favoured by audio connoisseurs as well as the board of directors of your local electricity company. Maximum bias is a principle here and duly requested to take care of low distortions. Or in other, somewhat more technical words: because of the amount of current that is continuously flowing through a semi-conductor the latter can always operate in the optimum range of its characteristic curve.
So, what's new and how are A-50V and A-60 distinguishing themselves with respect to handling and technology? Actually, the power stage is nearly identical with the exception that in 2004 new power MOS-FETs are shining from the two meticulously equipped circuit boards. The circuitry itself has not been changed. What is indeed new is the input stage which
Accuphase have dubbed MCS: Multiple Circuit Summing. This means that three separate
1
amplifiers for the input signal are connected in parallel in order to downsize noise and distortion to another record level.
One thing is for sure, namely that all these measures have nothing to do with saving money on the side of Accuphase, although one could have this idea as the amp comes a few hundred Euros less expensive than the A-50V, but this may be owed to the presently better position of the Euro against the Yen.
No "saving money" can also be recognized by the more or less relevant details,
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