Jeff Rowland amp in unbalanced mode

Hi all, does anyone have experience driving a Jeff Rowland amp (model 201 or any other) with rca-XLR adapters in unbalanced mode? Could you compare with balanced operation and was there sonic impact (I guess there will be, but how serious)? Did you use Rowland's own adapter? Thanks!
Just an FYI, you know you can use Jensen output transformers on your preamp to convert it to balanced. I know Rowland uses Jensen transformers in their gear - maybe that's what they're doing in their adapter.

Here's the transformer: DM2-2RX
Are Jeff Rowland amps truly balanced or do they just have an balanced input. Many brands of CD/amp etc have balanced in/out but every few of the are build 100% balanced.
Mordante - once it has input transformer it is truly balanced. Transformer has perfect common mode removal except for high frequencies where balanced input is defenseless anyway. To answer your question - Icepower datasheet for 200ASC (my Rowland 102) shows balanced input and I can see transformer inside on separate board.

Icepower switching frequency is too low (0.5MHz) to radiate and sharp switching pulses are filtered out by the output filter but nothing is 100% perfect and in addition there is still capacitive coupling. I would use common sense and for device that switches high currents at high speed I would use balanced cables with good shielding. My Rowland 102 does not even have unbalanced input - I respect Rowland's decision.
Kijanki, you hit the nail on the head, that is the exact reason for my question: the 201 hasn't got unbalanced inputs either, whereas I would like to use it with a pre-amp that has only unbalanced outputs. Nevertheless Rowland's manual mentions that unbalanced operation is possible with an adapter, so I am curious to find out if someone has tried this. Btw, thanks a lot for the link, Bob.
I can confirm that current JRDG amps are fully balanced in the input as well as in the output stages. According to Jeff Rowland, his amps put out an active signal on both positive and negative speaker terminals.

Hi Kijanki, have you considered adding a JRDG PC1 Power Factor Correction unit to feed your 102? I have heard that it is designed to enhance significantly its performance, but have not heard directly from anyone who has tried the PC1 on either 102, 201, or 501. PFC is already built into the Continuum 500 integrated, and the 312 amp. Guido
Guidocorona - There are two styles of class D output. One, like Icepower, uses single supply voltage and changes direction using mosfet full-bridge while the other style, like Hypex (Channel Island) uses two voltages positive and negative with mosfet half-bridge. First style sounds a little closer to tubes (even harmonics) but has half of supply voltage (DC) on both output terminals (doesn't bother me). Also bridging amps is not possible since it is already full bridge output. My small 102 has the highest bandwidth of the tree you mentioned and I don't listen very loud. I read your other posts on the PC1 and since you mentioned that my 102 is "eligible" I'm very interested. I have to upgrade speakers first (major expense) then I'll move to power supply. I'm sceptic about things like that, but I remember that at the beginning I was sceptic about interconnects and speaker cables - not anymore. Keep us informed! Is it expensive? I read review (AudioEnz) of 102/Capri and while Capri is better of two (exceptional) 102 is not bad, especially for the price.
Hi Kijanki, I looked for the Capri/102 review by Audioenz but could not find it. . . could you post the URL?
The PC1 is unfortunately not inexpensive, at $1500 list, but some dealers have sometimes offered a demo unit for quite a bit less. One good thing about it is that if you ever upgraded to 201 monos or 501 monos, the PC1 would serve there as well. Guido
Guido -
Thank you Kijanki, much appreciated. . . now I remember reading this review a while ago. Can't help thinking that the relative darkness, moderate downward extension, slight imaging problems, and other minor quibbles that Mr. Wong observed may have been caused by less than complete break in of the equipment. Capri is a bear to break in, requiring perhaps 1000 hrs. . . not sure about 102, but I wouldn't be surprised if it required more of the same. G.
I have a little over 400 hours on my Capri which I bought used. I'm not sensing any darkness or imaging problems. Detail is there in spades as well (at least enough detail for me). This unit is extremely quiet. I might agree that it is not the last word in transparency, especially in comparison to my previous K&K TVC and TRL Pre-1.5 preamps. For one thing the sound stage depth is a bit compromised, especially in comparison to what I experienced with the VAC Avatar SE which is the last unit I had in the system prior to the Capri. Overall though it is a fine preamp especially at used prices and mine having the phono option is bonus.
Clio, please keep us posted. . . I'd be curious what you think of Capri once you are around the 1K hrs mark. G.
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:
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
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
Guido - so it's entirely possible that sound improvements you heard are due to something different than PFC (wiring, shielding, power filtering, input transformer or mods to Icepower 1000ASP module). Often companies don't apply improvement to less expensive modules for marketing purpose (more money - better sound)
Guido - I forgot about another important factor - speakers. I heard that Icepower sounds great with some speakers (like for instance Usher BE-718) and not so great with others. It might be sensitivity to type of load speaker is presenting. Initialy first class D called class T had output filter outside of feedback having low Damping Factor and big dependance on the speaker impedance characteristic. Icepower has output filter inside of the feedback but nothing is 100% perfect. It would be great to compare 501 with 501+PC1 on the same speaker. How PC1 is attached to amp - is it external or requires mods to amp?
Kijanki, I suspect that the more refined sound of the 312 over the 501 is caused by a reasonably wide variety of technical factors, only one of them being integration of PFC. It is worth pointing out that PFC has now being integrated in the Continuum 500 integrated, which costs about half the 312 and also contains a Capri-like front end and some bulk output capacitance not implemented on 312. What frequently happens with technology is that novel design solutions are first tried in higher end devices, and then are gradually migrated to more attractively priced implementations. G.
Guido - I bought 102 + Benchmark to use only one pair of XLR interconnects (noisy environment). I decided against Bel Canto S300 since it was more expensive while not built as nice as Rowland. In my opinion Rowland's decision to put only XLR connectors was mature (not trying to please everybody). I know it wasn't for the savings of two RCA connectors since case is milled out from the single block of aluminum. Today I would probably go for Continuum 500 integrated.

I wonder if there are RCA-XLR adaptors for the output of preamp that preserve balanced cable configuration (transformer?). I know that people often have very expensive unbalanced interconnects and wouldn't change them. Transformers are not completely benign since they introduce small harmonic distortion at very low frequencies. On the other hand sonic difference, I heard of, is at higher frequencies, balanced being more "airy".
Good stuff Rafael. I don't plan to touch the Continuum's output, thank you. You raise one more good question to ask Mr. Rowland. Guido, will you do the honors?

Rafael and Dave, the active PFC circuit of the PC1 is in fact used in series with internal DC2DC transformers of compatible devices to optimize voltage regulation. Unfortunately I am not an electrical engineer and my technical knowledge is limited. G.
"Rafael and Dave, the active PFC circuit of the PC1 is in fact used in series with internal DC2DC transformers of compatible devices to optimize voltage regulation. Unfortunately I am not an electrical engineer and my technical knowledge is limited. G."

Hello Guido,
Yes, we do know that PFC must work with DC:DC converter. That was not a question. The qestions to which only Mr. Rowland can answer are:
1) is his DC:DC converter fully regulated
2) what is the peak voltage of the amplifier in quesion output (and what is its duration).

I am sure you undertsand these questions and you or Dave can ask Jeff Rowland for answer similarely as I ask Spectron people. If specs are good then nobody will hide them.

If I would read your writing above "... optimize voltage regulation" then it mean to me NOT fully regulated (just optimized) but I don't know if you meant it

Thank you
I'm a bit confused here - 200ASC module in model 102 is already regulated (nature of SMPS). Where PC1's voltage is injected?
Thank you Rafael, I may have misunderstood. . . As I am not an EE, you will get more precise answers by contacting JRDG directly. G.
Hi Kijanki, once again, I am not an electrical engineer, so I apologize for my lack of rigor. You are correct the PS of the ASC200 power conversion module is already regulated. Yet, according to the designer and to many users, feeding 102/201/501 devices 385V DC current through an active PFC unit, further increases their musical performance. G.
Thanks Guido
Hello Guido,

" will get more precise answers by contacting JRDG directly."

Sorry, I am (very) happy owner of Spectron monoblocks and if I would call to Mr. Rawland - I would just waste his time since I am not potential customer of his amplifiers and I don't want to do it - I would feel very uncofortable.

FYI, if interested, Spectron power supplies are linear and not fully regulated but as you eloquently said "optimized"
meaning among other things that the choice of aftermarket power cord will have sonic consequences.

We can probably answer this question. If your 312 and Dave's Continium 500 do not react to the choice of the pwoer cord then their power supplies are fully regulated - ...I think.

All The Best