From the 2006 archives: STAX DMA-X2. At last, an owner speaks candidly – Part 3 of 3

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Dear Howard:

I have been looking in the manual for the DMA-X2 and something my seller notified me about, has made me wonder about something. That the DMA-X2 is a true Class A Amp. can probably not be disputed, but whether or not it is a 600 watt Pure Class A (as you yourself describe it and probably and also most likely will be disputed.

Let me start by saying, that I thought that it was a 600 watt pure Class A amp as well – so it is of course with much regret, that I found this information in the manual. Believe me, there is nothing I would rather be able to say, than that it IS a 600 watt pure Class A amp. but I am afraid, that it is just not so.

I will scan and send you this file as soon as I get home, but as I am in Hong Kong right now, it is not possible for me. The manual says as follows:

The DMA-X2 has three stages. a Driver Stage (A0) which is a Class A Amplifier and a Final Stage, consisting of two parts, namely a stage one named (A1), which is a small Class A amplifier, but then, and this is the crucial part, the second stage of this Final Stage, is a big Dynamic "Swinging" Class A/B amplifier (A2).

Now what exactly this means I don't know, but my seller, didn't mean that the A1 stage was at more than about 20 watts. Now I think it is more than that, but then again probably not any more than a maximum of 100 W.

They also point out themselves, that is Stax, that they are not the only ones who has made amplifiers like this. Although I am sure, that this amp is one of finest in the world, it does send chills down my spine, when I hear this and makes me remember Technics with their cheating class AA principle from the late 80's and early 90's. Although I of course know that this is a huge insult to Stax and highly unjust, it still irritates me that Stax is not open about this and tells straight out, how much output the A1 stage has and how much the A2 stages has.

It reminds me more though of a more serious brand, namely Marantz, which in the same time period had their PM 64, 84 and 94 Mark I and II with their own system AVSS (Automatic Voltage Shift Supply), which as the name implies, shifted to the more effective Class A/B amplifier stage, when the volume and speakers demanded it. But they gave away the wattage of their amps. to be one quarter of the maximum output and so you knew more or less how much you had to go with.

What does Class-A with Dynamic Power Supply as Stax themselves describe it exactly mean?

With the DMA-X1, it was easy, because here they clearly say: Mono Class A/B power amp. And so here there is no doubt, because here they never claimed, that it was a Class A amp. but a Class A/B.

With the DMA-X2 I see it as more difficult, to exactly find out what this beautiful is. I guess in the long run it doesn't matter, as long as it sounds good, I just thought it would be nice to cast a light on the description of this amp. as it might not be completely correct, when it is described as a 600 w "Pure" Class A amp. if it is really not.

Sincerely

Thomas Lerche.

thomaslerche@hotmail.com

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