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Romy the Cat wrote:

I did not say how my saga with APS Pure Power regenerator finish but it never finished. Since the end of the last year the regenerators is sitting in my closet and I have sent the unit’s main board to APS people for the “revision” as I do not feel it was useable. I still feel that the direction that APS are trying to go hugely perspective and I wish they found how to do the Class D regenerators to be stable, and producing right sound. It looks as the APS has revision of their board that might fix the problems that they had. I do not have a lot of hope but who knows they might did it accidently. The dilemma that I see is that the APS engineers do not work on the specific sonic problems that I pointed them out but they works against one list of improvements. It is valid list and they might do good job with this improvements but they are completely clueless about the sound of the units and the main purpose of this unit. The Chinese guys who as I understand are responsible for ingenerating aspects of the unit do not even acknowledge that problem with the unit. It is very frustrated as the only contact I have with APS is via the Canadian Director but he does not look like have enough pull (or desire) to address the problems with sound as long the unit is being sold well. So, that hope I have so far that the Chinese folks doing their planed modification might accidently to fix the problems that cause of the APS generator to have sonic aggravations.

The unit that returned to APS last December has a number of sonic “issues” (well coved in my comments) and one objectively bad problem that I feel was a fault of assembling and I feel that sonic problems were deriving from it. The regenerator #5 has a huge voltage linkage between neutral and ground. It is not a symmetrical devise but it had 67V between hot and ground and 53V between neutral and ground. It had very far off sound and what I got my current regenerator #6 the very first think I did was checking the propones of AC polarity and absents of voltaged super-linkage. This time the PurePower unit had 120 on Hot and 1.1V on Neutral . The  1.1V is slightly high, I would like to see 100mA-300mA but it is not an end of the worlds and considered that the problem with voltage linkage was resolved.

The unit also sound much softer and with much more polite “Super Structure” then the regenerator #5. In fact it was quite good out of box. (The unit is keep running for the last 3 days). From my past experience I knew well what the PurePower regenerator, so I quickly run over all my all familiar configuration confirming that the this unit #6 has no own “issuers”. The results are following: Bidat D/A,   Lavry D/A, Lavry A/D,  DAW machine,   Placette Preamp, CEC TL0 transport, Sansui TU-1X and REL tuner are very nice on APS power. The Pacific Microsonics Processor and Rohde & Schwarz tuner and the “End of the Live Phonostage” break up sinusoid very unpleasantly. The sound of Pacific and Schwarz get worse with PurePower. The sound of the Phonostage does not get worse even the sinusoid get twisted. Whatever it worth: the Phonostage has input filter, the Schwarz and Pacific do not. I did not even try to use my power amps: the APS folks and I mutually agree that my power amps are a taboo for this regenerator.

I ran the system from the regenerator connected to a power meter. Exactly like before I confirmed that the PurePower unit shell not be loaded more then with 200W for sonic consideration. My regular load was 100W and it looks like was even better then 200W. This unit #6 has an experimental feature that allows manual adjusting the depth of regenerator’s feedback with regard to the specific load. This is VERY good and very smart functionality as with class D amp feedback is something that set the stability of regulation and it effectiveness certainly affected by load. Experimenting with different loads I was able to see how the change of feedback’s depth changes the stability of the wave’s summit. However, I was pretty much in the same corner of feedback attenuator. Perhaps it is because I did not run the unit in the very different load conditions… like 70% or 90% of load. Also, I did not detect a whole lot of sonic changed with change of feedback. I changed the load from 50W to 150W that the regenerator might recognize as the “same load”. I presume that if I change the load from 50W to 900W then the feedback attenuator and observing the wave shape change with load might be more affective.

The most ugliest but partially relevant features that all APS units had still exist in my current regenerator. The PurePower returns back to the source power line a LOT of noise. I was not able to use PurePower on my dedicated lines as it craps it out inhumanly power for the rest components that are not connected via the PurePower regenerator. The cure is to plug the PurePower in house utility line, keeping the dedicated audio lines free from the PurePower’s returned noise. If not to do it then this noise is EVRY much visible on scope and it is very nasty.

OK, everything was fine and I might do into the sonic nuances of the PurePower unit. The PurePower drives a lot of switching nose from output. It has the filters but they help only partially. Adding capacitance to the PurePower’s output minimize the noise. In the past I bough specialty for this task some high-frequency-optimized caps and I put them in the game. The PurePower filter has CLCLC filter with 1uF caps. Adding 6uF kills all noise. However, it also softer bass and eats dynamics. Experimenting further I concluded that approximately .5-1uF extra capacitance does OK and it looks like doe not crap dynamics too much. Then I discovered something even more interesting. The PurePower use some ferrite chokes on the cables between the units sections. However, it uses ferrite bagels on both wires suppressing the HF noise across common mode. The differential noise between the hot and neutral wires is not suppressed. I have a lot of ferrite left over from my Tuner/DAC project.

http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=7851

 http://www.GoodSoundClub.com/TreeItem.aspx?PostID=7949

…so I put some of them on the individual wires – the result was very-very positive – I did not expected even how effective it would be.  So I went to extreme and load the each inch of the free output cable in the unit with a LOT of ferrite suppressors. In fact there is a lot of empty space in the PurePower unit and am planning to order a twice-trice longer cables (between the generator and output filters) and put there insulting amount of ferrite, both in common and deferential position. With what I did load with ferrite the init was very nice with practically no need to add caps to the output. The ferrite kept the “super texture” but took the edge out of it – very nice and gentile effect. I need more ferrite… where this damns cheap Russian surplus suppliers where one you can barter a railway train of ferrite cores for a bottle of vodka…

I was listening and I kind of like what I heard and I decided to finish up any further experiments and let it to be. I unplugged all cables, suck doe the regenerator, picks it up and dumped it in my closet – where I was intended to sit driving the system via the extension cables. I installed the PurePower and without even connecting any input of output cables I stated the unit from own buttery. Well, it was the last time when I saw it working. The unit started, in 2-3 second it heard a click insider the unit’s chasses and in a few seconds the air of closet begin to fill with the small of coked electronics. What the fuck!!! The unit went down, it was restated but there was no voltage at output – so it looks like the output stage was burned. I have to tell you that I was so disappointed that it hard to explain. I was trying to call to APS folks, it was Saturday and they were not there. It was kind of good as I was so pissed off that I could tell them something that we both were not be happy later. Why this fucking regenerator keeps blowing up? This is 6th unit and 3 of them ended up in flames!!! Is it cursed or it is just faulty designed? I do not know the answers.  If my 2nd  PurePower unit blew up what it started my power amps then the unit #4 and #6 blew up totally without any explanations! From one side the APS people are fine and cooperative dealing with this type of problems but the downtime and the annoyances with shipping and replacements are …. the annoyances. Not to mention that since the last June when I started experimenting with PurePower I did not have even a whole week of a properly functioning APS regenerator in my room. Is it too much to ask?

I truly do not know what to do now. It looks like the PurePower idea might work but it must work persistently in order to be usable. The APS folks admit that under specific conditions the PurePower might blow but they connect it only with exercise in-rush current. In case of my unit #4 and #6 I had no in-rush current, in fact the unit #6 was not even connected (!!!). What I need to do next – to fix it and to pray that it will not blow next time? The APS people claim that their new 2000W regenerator immune to burning out. I do not know if I feel comfortable to believe to it. The reason this damn regenerator is blowing is because there is insufficiently designed protection.  How difficult in case of any problem to shunt the regenerator with 100-150A diode? The diode switches at nanosecond sped that would take a fraction of cycle – and solid state device will not have time to get overheated… Anyhow, I do not know what to do now. I know that I would like to USE the PurePower unit in my system, not to spend my time to write the stupid post at my site about the damn regenerator’s flames. It begins to annoy me… The second summer is coming through and I still stupidly waiting for the PurePower’s freaking miracle….

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