Jeff Rowland amp in unbalanced mode

No problem Guido. Rather on the contrary, thanks a lot for pointing out the differences between those amps. If I'm looking at the pair of JRDG 201 presently offered at a bargain here, it is out of pure curiosity as it would be my first acquaintance with Rowland as well as my first acquantance with switching amps. Noticing you put them in the more "sterile" (just to categorize them, I know we may be talking about nuances) group, it might turn out to be a bit of a disappointment, especially since I would have to drive them in the unbalanced mode that Rowland themselves obviously consider not to be the optimum. Have you ever heard the Danish made Acoustic Reality IcePower amps, in particular the eAR 1001-REF mono blocks? (Or perhaps someone else, reading this thread?) They are moderately priced (factory sales), the specs are interesting and they look very stylish - actually quite "icy", but I wouldn't want to judge the book by the cover.

Power Factor Corrector, PFC:
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Hello Guido,

I have noted that you and Dave endorse Jeff Rowland PFC with emphasis on 385 DC voltage. However, this is not "real" voltage.

The PFC allows the power supply to draw a sinusoidal current from the mains. This will reduce electrical pollution and highly spiked currents that can generate undesirable harmonics from the amplifier to the other equipment. Consequently, the PFC minimizes the harmful electrical and nasty audible effects of many older traditional power supply designs. Also, the PFC reduces the need for filtering; Finally, there must be a small energy storage capacitor which may or may not be used for energy storage. These are positives of PFC.

The PFC output is, indeed, 380 to 400VDC but it is NOT isolated from ground i.e. - you touch it - you dead (DEAD). To isolate it from ground, requires a DC:DC converter which has a transformer isolation. The output voltage from Dc:Dc is a "real" voltage and you better ask your favorite manufacturer what is it and much more importantly - is it regulated. In other words PFC is semi-regulator and DC:DC converter, in theory, can be fully regulated. In traditional liner power supplies, the partial regulation can be better then PFC - its not easy but best linear power supply have it....

If you want to share with us what Jeff Rowland does with PFC output then it will be very interesting.

Thank you in advance.

All The Best
Rafael

Hi Karelfd, unfortunately I have not had the opportunity of listening to the Acoustic Reality amps. It is my understanding however, that most switching amps are truly balanced designs. I suspect therefore, that no matter what amp of this type you adopt, you may not be getting their musical best in a single ended configuration. This is purely an educated guess on my part, and if anyone has had any direct experience one way or an other, please post your findings here.

Guido - I don't thing is changing anymore but I haven't counted hours.

I wonder what came earlier 312 or 501. It is possible that Rowland requested (or made) some changes to Icpower module based on previous experience. There are also some external components like input transformer and possibly mains filter. It would be interesting to listen to the same amp with and without PC1.

As for steril sound - my experience is very limited but I suspect that very clean sound might create impression of sterility or lack of dynamics (distorted guitar is lively in comparison to clean jazz guitar). When I upgrated from integrated solid state amp to Benchmark DAC1 + Rowland 102 I got impression that some instruments are missing - it sounded too clean.

Hi Kijanki, 501 were introduced prior to 312. Both use ASP100. However 501 monos are relatively basic design, while 312 costs almost 3x the 501s, and is much more sophisticated and, includes integrated PFC among other things. G