Class A multi-channel amp?

El: Simulating tube sonics in a SS piece of gear typically means slower response times and less control of the drivers. This softens the leading edge of instruments, making them sound "less aggessive" or "more enjoyable" ( especially with typical digital recordings ). At the same time, you end up with a rounder, warmer bass. This tends to fill in the lack of body that many hard, cold and sterile digital recordings suffer from. Both of these are colourations related to poor technical performance but could be pleasurable to listen to.

As far as the distortion characteristics of the amp go, i think that John Curl measured phenomenally high levels of distortion on both odd and even orders, making this more like a poorly designed Integrated Circuit ( IC ) based component than a tube or Class A design.

While i may sound like i'm attacking / belittling these amps, the bottom line is that you like and are enjoying them. Who cares what i or anyone else thinks. Sean
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sean...I have heard it said that conventional testing techniques get screwed up in ways that I don't recall, when used on digital amps. Who knows?

"Less control of the drivers" means higher output impedance. That I can understand. But what does "slower response time" mean. Surely response time is defined by slew rate which is indirectly specd in terms of frequency response. HF response of tube amps is limited by transformer performance, and PWM digital amps do use filters to remove the switching artifacts, whereas conventional SS amps have to have a small inductor at the output to avoid becoming radio stations. So the digital amp may indeed roll off above 20Kc like a tube amp.

It is the stated intent of the zr1600 designers to emulate tube class A sonics, and several reviewers have suggested that the goal was achieved. I don't have a set of 600 watt class A tube amps handy for comparison, so I suggest that you lay hands on one of these digital amps and see for yourself. The cost will be less than the wires to hook it up!

El: many switching amps have gone to a design that uses a very high / fast switching frequency. This moves the potential for in-band noise of any measurable amplitude further away from reality. As such, some such designs offer excellent linearity out to well beyond 80 KHz or so with minimal distortion. If everything is done right, that means that the amp will have the speed to pass a square wave with good linearity up to at least 8 KHz. Anything above that frequency, in terms of musical notes or test signals, would be hit or miss depending on the individual design.

Other units, with a lower switching frequency, lower hinge frequency for the filtering, poorer transient response, lack of stability with diverse loads, etc... tend to produce high frequency roll-off and in-band phase shifts at frequencies that are closer to mid-band reproduction.

My guess is that you personally know all of this, so we are pretty much discussing this for the edification of those that aren't as familiar with such things. : ) Sean
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sean...The Carver amps, and some others, but not the Spectron, reportedly use variable ("spread spectrum") pulse width up to more that a megacycle, and this somehow means that the supersonic filter can be less abrupt. Do you have any further clarification on this?