Jeff Rowland amp in unbalanced mode

Guido - 102 took close to 400 to break in. My setup so far is a little bit crazy since cables are the most expensive part of the system (Acoustic Zen Absolute XLR, Acoustic Zen Satori Shotgun) but I treat them as non-perishable items and therefore invest more for the future. Acoustic Zen Satori has a little "round" lower midrange which is blessing with Icepower. Lean sounding cables should be avoided. Strange (sterile?) top end according to many people is in my opinion related to limited bandwidth of Icepower (102 ~ 80kHz, 201~ 65kHz). Bandwidth limit is introducing some phase shift at 20kHz and perhaps wrong summing of harmonics. Other explanation?

Hi Kijanki, has your JRDG 102 stabilized completely after 400 hours mark?
I also have observed some treble sterility -- or at least
lak of ultimate musicality -- in some 'entry level' switching amps such as Flying Molde (by far most evident), Channel Island, JRDG 201, JRDG 501. Conversely, JRDG 312, Spectron Mus 3 SE, and to a great extent NuForce 9, are capable of a very delicate and nuanced treble. I have not heard the 102 myself, so I cannot comment on it directly. I can't comment on phase shift above 20Khz because my technical knowledge is very limited. The solution that JRDG has adopted to addressed the perceived harmonic sterility and somewhat moderate microdynamics of raw ICEpower modules is to feed the 312 and the new Continuum 500 a 385V DC through an internal Power Factor Correction circuit in front of the power supply. I have done comparative a/b/c listening of 201, 501, and 312, and the latter sounds more graceful and musical by miles, with no hint of sterility. The external PC1 unit does the same thing for the 102, 201, and 501. . . but 2 units are apparently recommended for use with the 501 monos.
But now I realize I have at least partially hijacked this thread, as my last couple of posts have nothing to do with single ended operations. . . my apologies. G.

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.