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The load that I used everywhere was pure restive load. Not good at all…. Also it would be worth to note that the unit with increase of load better filter the switching frequency of the D-amp.

Well, the oscillator itself does not care of course about the load. The class D-amp usually has very little distortion as well. The wave on the scope bends quite aversively for a few seconds what the load changes and it takes 2-3 seconds to stabilize. So, I presume that the people out there who would use the PurePower with class AB amps that drown all time different current should have a lot of fun…

I consulted with Dima and he told me a lot about design of this unit and he proposed a half dozen of problems that might cause it, naming the most likely the problem with the AC filter that the APS has after the digital amp. We discussed a lot of the idea of this filter and we agree that it is very hard, if any possible, to make this filer to operate properly with different load.

Theoretically it would be possible, if I own the unit, to open it up and to rebuild the failing filter for a very precise current that my entire playback would drew, perhaps even making the experiments with the type of the filter and the order.  But I am not in the business to build the damn regenerators. The entire idea to pay $2.500 to APS people is not to have a $3-worth oscillator with $40-worth off the self digital amplifier but rather to have out of box complete sonic solution. If need to rebuild the out filter then what I am doing?

Frankly I am very much egger to hear from the APS folks that I need to look at the unit and count some capacitor or coils at some kind of board and then we learn that one coils or caps or power resistors from the output filter was missing. It would perfectly explain the ringing of the filter during and after the switching. The fun would be if we fix the ringing and tame the sinusoid shape … but loose the quality of Sound…

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