Jeff Rowland


I recently replaced my Parasound A21 with a JR M525. It has taken my system to new levels: soundstaging, spacing between instruments, tonality, and a natural midrange. The M525 is the first amp I've ever owned that presents a 3 dimensional soundstage. All that being said, now I wonder what improvements going from the M525 to the JR S2 integrated or bridged M525s will yield? Is it a night and day difference? Are bridged M525 better than the S2? My system: Aerial 7Ts, PS Audio DirectStream DAC, Bryston BDP-2, and all Wireworld Silver 7 cables.
ricred1
I'm not familiar with the specific amp, but in general I would not expect a bridged amp to provide good results when driving your particular speakers. As can be seen in the impedance curve shown here, the impedance of your speakers is in the vicinity of 3.5 to 4 ohms between 50 and 100 Hz, where lots of energy is often required, and is close to 3 ohms around 25 Hz. In bridged mode the amplifier will "see" a load impedance equal to half those values, i.e. 1.5 to 2 ohms, and of course most amps will not perform at their best when dealing with such low impedances.

Regards,
-- Al
Al,
Thanks for the technical information. Now it makes sense why Rowland was hesitant to say for sure bridged 525s would work.
Al is right (as usual). This amp most likely uses PASCAL S-PRO2 class D modules. Data sheet shows minimum load of 2 ohms or 4 ohms when bridged. Bridging might create problems with your speakers gaining only about 20% of loudness. Not worth trying IMHO.

http://www.pascal-audio.com/downloads/S-PRO2_Datasheet-1_20.pdf
Hello Al, Ricred, Kijanki, and all,

After reading this thread, it has led me to question my intention of using a second Class D CDA 254 amplifier, thus allowing me to use the two of them in bridged mode as monoblocs.

My speakers are of course different, they being Tannoy HPD 315's, 94 db sensitivity and 8 ohms. I don't know if you can draw any conclusions without specific test results, which in any case, wouldn't be available.

My particular application of these drivers are in custom 150 liter bass-reflex enclosures.

I have written to Tom, at Class D Audio, about this, but the expertise available here is without peer.

I'll be thankful for any information that can be provided.

My apologies to Ricred for hi-jacking his thread.

Regards,
Dan
Those Wireworld cables have a lot to do with your system's excellences
Stringreen,
Do I detect a little sarcasm in your comments?
Richard, the safe/conservative approach is not to add a second M525 chassis for a bridged configuration, but to move up the chain instead with an amp that inherently delivers greater power....

Within the Rowland line, that means the Continuum S2 integrated, which is also said to enhance all those audible parameters that you already like on M525.

On the other hand, there are reasons why Rowland was comfortable enabling bridging via a simple toggle on the rear panel... According to all reports I have heard, M525 in bridged mode does not degrade the sound quality, and delivers larger stage/images, and greater authority.

Of course, things might be different with speakers having relatively low impedance.

G.
Hi Dan (Islandmandan),

I found this impedance curve for the HPD 315he, which confirms (as might be expected for a Tannoy) that its impedance characteristics are very benign. (If the link just opens at flickr.com instead of opening at the specific photo, paste the url https://www.flickr.com/photos/89700142@N03/8344329373 into the address bar of your browser). Note, btw, that in contrast to most such curves that are presented this one extends down to 1 Hz. So the somewhat low impedance magnitudes at the left end of the curve essentially represent DC resistance, and are reasonable values that can be expected to be inconsequential.

I also looked at the web pages on the amp module and the kit, and the manual.

The bottom line is that I don't doubt that the amp can drive the speaker in a reasonable manner in bridged mode, but of course how the resulting sonics would compare with stereo mode is speculative.

Another possible concern, though, is that I note that the amp module's input impedance is spec'd at a low 7K, and I suspect that in bridged mode it is likely to be around half that amount, or only 3.5K. That will be non-optimal for many preamps, especially the many tube-based preamps which employ coupling capacitors at their outputs, the capacitors typically resulting in substantial output impedance rises at deep bass frequencies.

But if you don't specifically envision an impedance incompatibility with the preamps you may use, given the very low price of this kit it would seem to be a reasonable risk. Also, perhaps it might be helpful in reaching a decision to try providing the kit you already have with a mono signal and running it in bridged mode with one speaker.

Best regards,
-- Al

P.S: Kijanki, thanks for both the input and the compliment :-)
Al, thank you. You have done your usual stellar job of research, before providing a helpful and informative answer.

It looks like the only issue will be the output impedence of my Transcendent Sound GG preamp. I used a 100 ohm Goldpoint stepped attenuator, what comes in the kit is 200 ohms.

Al, your idea of trying one speaker in bridge mode is a good one, I believe I'll try that this evening, and see how it goes.

Thanks and regards,
Dan

Ricred1, I stated 22% loudness increase, but it would be true for 2x loudness. I forgot that bridging doubles the output voltage, thus quadruples the power. In such case you can count on (substantial) 49% loudness increase. Speaker's minimum impedance remains the problem.

L=k^(1/3.5) where L=loudness, k=ratio of power.

L=4^(1/3.5)=1.49
A sincere thanks to everyone who took the time to respond. This thread is representative of how posting a question can be of value...at least to me! I asked the same question to Jeff Rowland technical support and a dealer. I'm disappointed that they didn't take the time to look up my speakers and explain why bridging the 525s may not be the best option.
Ricred1, I found them very eager to help. Perhaps it was just the particular support person. Fortunately we have this forum to learn and share
Well I'm 95% sure I'm going to get a Capri S2. I love my current sound, but I go direct from my Directstream DAC to the M525. I need the additional gain from adding a preamp. I just hope adding the S2 doesn't degrade the sound.
Hi Richard, I do not expect Capri S2 to degrade the sound, but it is likely to modify the tembre very subtly.... Based on my memory of Continuum S2, which includes the Capri S2 linestage circuit, Sound might become slightly warmer, and probably the bass might acquire a little more body.... All of this after appropriate break-in of course.

If you get Capri S2, will you also get the $400 DAC card for it? I have heard that it is quite a treat!

G.
Hi Ricred1,
I used to own the Capri S2 with the DAC card option. Since you already have the PS DS DAC, the dac card option would be redundant. That said, my experience with the Capri S2 while I had it was pleasant until I replaced it with the Ayre K-5xeMP preamp. The problem with thinking that something is good is that you don't know what you are missing until you have tried something else. With the Ayre preamp in the chain, the loss of dynamics, transparency, resolution and extension in the highs with the Capri S2 all becomes woefully apparent. My humble advice is, if you can, to audition at home in your system both the Ayre and Capri S2 before pulling the trigger.
Regards. J.
G.,
Slightly warmer is fine, I don't want to loose detail, imaging, or the three dimensional soundstage. I already have a PS Audio Directstream DAC; therefore I don't need the DAC card. If your suggesting the DAC card is as good as my DAC, I would just get the S2 continuum with DAC card, because I could sell my DAC and M525. I want to do what make the most sense to improve the sound, but I don't have an unlimited budget.
Via email, you stated :-
"Thanks for the Ayre K-5xeMP suggestion. How much is it? My current system needs more bass impact. I submit my issue is I'm using the DAC as a preamp and it acts like a passive preamp and I loose gain/dynamics. Everything else is fantastic...imaging, detail, three dimensional soundstage. Any suggestions? What amp and speakers do you have?"

"Hi Richard,
It's $3500 retail. JA/Stereophile rates it full Class A. I am using Bryston 28B SST and VA The Music speakers.
The Ayre will give you the gain/dynamics, bass impact and airy, transparent highs that you want.
The JR house sound including the power amps, is slightly dark with rolled off highs. Cheers! Jon."

Just to add to our email exchange above, you won't be losing "detail, imaging, or the three dimensional soundstage" with the Ayre. But with the Capri S2, you get less of these compared to the Ayre.
Jon2020,
Yes, I sent you an email and didn't "post" my question. If you feel the need to post my "Private Message", you should post all of it. In addition, I said,"The JR M525 is very detailed, I compared it to a bryston 4bsst2 and parasound A21...both had more bass impact, but not the 3 dimensional soundstage. My other option was to bridge the 525, but I'm concern about the impedance of my speakers.
I'm confused, I read glowing comments from you regarding the Capri?" Because I can't listened to everything, I post questions to provide food for thought and then I make my decision. I'm not into trashing or glorifying one company over another. Audio is subjective and I've learned there are no absolutes in audio. Thanks for your feedback.
Didn't expect this at all.
My apologies, Ricred, if I have unintentionally offended you. I have posted what I thought were relevant parts of your message only for the benefit of others following this thread. I was not trashing one product in favor of another. I was merely relating my personal experience with the Capri S2 vs Ayre K-5xeMP. Yes, audio indeed is very personal. The usual "to each his own", then.
Good day ahead. :)
Hi Richard, the universal "true truth" non existing in audio, the ultimate beauty for one person is sometimes "not my cup of tea" for another one.

So for example, while Jon feels that the Rowland sound is somewhat dark and rolled off at the top while AYRE is extended and thusly preferable, I feel that Rowland yields my preferred kind of extended range and extreme musicality, while I perceive AYRE to be excessive in its highlighting of treble, and in fact can't listen to AYRE for more than a few minutes at a time.

Who is right and who is wrong... No one really... It depends on how we perceive sound and what turns into greater beauty in our mind.

Concerning removal of detail, I fear that any preamplifier you place in the chain is of necessity a compromise: it will inevitably remove microscopic amounts of detail, and is bound to modify the sound in some way. The issue that one needs to address is... Does the change of a particular preamp enhances your experience of beauty in sound, or overall does it detract from it?

And sometimes... Does the house sound of manufacturer "A" meet your conception of nirvana more than manufacturer "B", or viceversa, or... none of the above?

G.
+1, G.

Try before you buy, whenever possible.
Synergy is king.
G.,
I take everything I read with a "grain of salt." I understand that everyone has their biases. I love the Rowland sound, but I'm lacking bottom end and I'm trying to find the most cost effective way to correct it. It could be the Rowland or a combination of the Rowland and Directstream DAC. I've read comments regarding the Directstream's lack of bass reproduction. I don't know if adding a second 525, a preamp, or going to the S2 Continuum is the most cost effective way forward. If the DAC chip is that great, adding the S2 continuum is the most cost effective.
ricrd...no saracasim intended....I love Wireworld stuff..use it myself. I have also used Rowland (know Jeff peronally). Excellent company....I always look up to Mr. Rowland.. (He's very, very tall :)
I remember the 7T's though very good speakers didn't have the bass that I thought it would have, by looking at the speaker. Have you thought of adding a sub?? A powered sub would make the main speaker sound better too.
Ricred, what can often be a very major contributor to lack of bass impact is the acoustic effect of the rear wall (the wall behind the listening position). I can't tell from your system description photos what that distance is, but under typical indoor environmental conditions rear wall reflections will produce a suckout (i.e., a lack of bass) centered at a frequency in Hz of about 282 divided by the distance in feet between the listener's head and that wall.

So if you were say five feet from that wall, there would be a suckout centered at about 282/5 = 56 Hz. In my experience that effect can often be MUCH more significant than differences in bass performance between most electronic components.

Good luck as you proceed. Regards,
-- Al
03-07-15: Kijanki
Ricred1, I stated 22% loudness increase, but it would be true for 2x loudness. I forgot that bridging doubles the output voltage, thus quadruples the power. In such case you can count on (substantial) 49% loudness increase. Speaker's minimum impedance remains the problem.

L=k^(1/3.5) where L=loudness, k=ratio of power.

L=4^(1/3.5)=1.49
Kijanki, that's not true over the entire amp power range, correct? it will be true for a small power output range until the amp runs into its max current capability. So, we'll see a 4X the power just for that small power output range.

when the amp output voltage doubles so does the current. So, you have 2X voltage & 2X the current & an increased heat dissipation (& maybe even amplifier catastrophic destruction).
Or, am i thinking of this incorrectly? Thanks.
always look up to Mr. Rowland.. (He's very, very tall :)
indeed he is. I met him at the 2013 RMAF - on Sat he was running the demos himself in the afternoon (had the 525 amp driving the Raidho stand mounts which were crazy priced). I'm tall but no comparison to Jeff Rowland himself....
Almarg,
Speakers are as follows:
the rear of the speakers are 4' 2" from the front wall
8' apart, 4' 8" from sidewalls, I sit 10'away, my head is 6'away from the rear wall
I have 2 GIK Soffit Bass traps in each front corner from floor to ceiling, 6 GIK 242 panels-2 each on the left and right at the first reflection points and 2 on the ceiling
Stringreen,
I just had a discussion yesterday with a friend regarding adding a sub. The thought was to add a JL F112. Unfortunately it would cost more than I currently want to spend...I don't have a preamp; therefore I would need to purchase the JL F112 and preamp. In addition, I never really liked subs. Years ago I had an Martin Logan Depth i and a HSU sub. Neither one blended well with the speakers I had at the time.
Jeff is a very nice man and makes time for less fortunate people. He is not a personal friend. I just have seen him at some dealers and have been to his company with other retailers and got to see his operations and visit with him at times. So I know of him. I am not a retailer and never have been. I have just got to enjoy others in this hobby. Jeff also has a great ear for what is natural. I think very highly of his electronics. I have been on the look out for a long time for something from him and just havn't done it because of cost. But hopefully someday.

But for Ricred. I don't know if this will help or not. I use a buffer after my passive attenuator and it does fill out the bottom end in a very nice way and does not leave anything negetive to speak of. I don't know how this would work out for you. What I have is a Burson AB160. It is made with quality discrete components. I think that may be why it seems like it doesn't have a sound signature of it own yet fills the sound out. What I think I mean is it doesn't seem to lose any transparency yet it makes everything sound more full or complete. I have always liked the less is more plan. It has always worked out well. So I was somewhat surprised that this buffer was such a benefit for my system. Chris Johnson of the Parts Conexion(former Sonic Frontiers owner)said this Burson AB 160 was the cadillac of buffers. For whatever that is worth. And that happens to be what the Burson sales stuff says it is suppose to do. And suprise it seemed to meet up to that for me.

That being said they don't make them any more. And I don't want to give mine up for almost anything I have heard(6 preamps)under 8000.00. Sometimes they have shown up used. Burson may have a better replacement for it. I don't know how it could be much better but I have been wrong before. Anyway just a thought.
03-09-15: Ricred1
Speakers are as follows:
the rear of the speakers are 4' 2" from the front wall
8' apart, 4' 8" from sidewalls, I sit 10'away, my head is 6'away from the rear wall
I have 2 GIK Soffit Bass traps in each front corner from floor to ceiling, 6 GIK 242 panels-2 each on the left and right at the first reflection points and 2 on the ceiling
OK, so rear wall reflections will result in a suckout centered at a frequency of 282/6 = 47 Hz. It's hard to say how far above and below that frequency the suckout would extend to an objectionable degree, but I wouldn't be surprised if the affected frequency range is wide enough to be a significant contributor to the issue.

For experimental purposes, just to gauge the significance of that effect, if practical you might temporily relocate the two bass traps that are in the front corners to a position such that both of them are in a line extending directly back from the listening position. Perhaps one immediately behind the listening position, and one up against the wall. And it would probably be most useful to compare sonics between having the traps in that position and having them out of the room altogether, so that the comparison wouldn't involve changing two things at once (i.e., moving the traps away from the front corners, and placing them behind the listening position).

Also, again for experimental purposes, you might try to determine how severe that effect seems to be at differing listening distances. In doing so, it might be helpful to purchase a test CD, such as this one, further described here. Track 17 would facilitate assessment of frequency response flatness in the bass region.

Bombaywalla, I agree with your comment. It would be unusual for an amp to be able to fully quadruple its max power rating into 8 ohms when bridged, much less into 4 ohms, due to the current and thermal limitations you referred to. Although for an 8 ohm load the OP's 525 comes surprisingly close to doing that, the 8 ohm ratings being 250 watts and 950 watts for stereo and bridged modes respectively.

Best regards,
-- Al
Almarg,
Thanks for taking the time to provide assistance. You are a smarter man than me!!!I moved the bass traps from out of the corner and put them behind my listening position. I promise I'm not exaggerating...my wife was downstairs and game upstairs. She said,"I knew you did something, because it sounds so powerful downstairs." I haven't move the bass traps out of the room, but I will do it tomorrow. It addition, to more powerful bass, I hear more detail. The question is why? I thought bass traps were good?
Almarg,
My other question is about the volume control on my PS Audio DSD DAC. I guess it operates as a passive preamp; consequently I need to turn the volume up to 70-80 for it to be adequate(70 normal listening, 75-80 loud). How does that affect the amplifier? Would it sound better with an analog preamp?
The output of the DirectStream DAC is transformer coupled, and in that sense can loosely be considered to be passive, but unlike resistive-based passive preamps it has an output impedance that is low enough to be comparable to that of most active preamps, both tube and solid state. That is confirmed in John Atkinson's measurements.

Given that, as well as the 40K balanced input impedance of your amp, as well as PS Audio's claim that its volume control mechanism does not lose resolution at any setting (which if it occurred at all would occur at low settings of the control, not high settings), I see no technical reason that would call for the insertion of a preamp. Which is not to rule out the possibility that you might find adding a preamp to be subjectively preferable. But FWIW my own bias is to put the burden of proof on adding anything to the signal path that is not clearly necessary, and in this case I don't see it as being clearly or technically necessary.

The reason for the relatively high settings of the volume control you are using are most likely the combination of the "full scale" (maximum) output voltage of the DAC being a bit lower than usual, and the sensitivity of your speakers being somewhat low (Stereophile measured the speakers as 86.6 db/2.83 volts/1 meter, which for their 4 ohm nominal impedance is 83.6 db/1 watt/1 meter).

So as long as you never find yourself wanting to turn the volume control up beyond the top of its range, I wouldn't attach any significance to the fact that you are using it in the upper part of its range.

A couple of things to check, though:

1)Apparently the DAC's output can be set to two different levels via the menus. Check to see that it is set for the high level, i.e., that the output attenuator that is provided is deselected.

2)Check that the unit has the latest firmware (version 1.2.1) installed. User comments as well as PS Audio indicate that that update tightens up and improves the bass. I would expect that you can determine the firmware version somewhere in the menus, or perhaps it is displayed briefly at startup. If it is an earlier version, you can easily download and install that version per the instructions at PS Audio's site.

Regarding the bass traps, it's of course sometimes possible to have too much absorption in a room as well as too little absorption, especially from a subjective standpoint, and depending on the speakers, their placement, etc. I suspect that the main reason for the more powerful bass reported in your latest posts was removal of the traps from the front corners, rather than their placement behind the listening position, in part because the change was perceivable at other than the listening position. Hopefully after doing the remaining experiment (removing the traps from the room altogether), and some further listening, you'll be able to determine which of the four possibilities is preferable (traps or no traps in front; traps or no traps in the rear).

Continued good luck. Regards,
-- Al
Bombaywalla, You are right - not many amps quadruples or
even doubles power exactly. I don't even care for the one
that does, since in order for this to happen amp has to have
hefty power supply but also lots of negative feedback.

On the other hand listed power specification is useful only
if you listen to sinewaves. Music demands very little power
on average, since half of the loudness is 10% of the power
and music has gaps. Heavy orchestral pieces might demand
more power but Jazz trio needs very little. Maximum current
is perhaps more important. Power specifications are very
vague. It can be FTC, EIA, CEA or no standard at all. FTC
defines amplifier's power when both channels are driven over
full audio band 20Hz-20kHz for 5 minutes after one hour
preheat at 1/3 of power and meeting listed distortions. EIA
requires test at 1kHz and 1% THD without preheat for one
channel only (not sure how long). CEA test requires 5
minutes at full power at 1kHz without preheat, while other
channel is driven at 1/8 of max power (why 1/8 ???). Most
of class D amps would not even pass FTC test, having very
limited power at high frequencies. The only class D modules
manufacturer I know that specifies full power bandwidth is
PASCAL but it is useless anyway since music demands very
little power at high frequencies, not to mention size of the
tweeters. Most of manufacturers don't even specify what
standard, if any, they use for testing. For instance
Icepower module in my 200W Rowland model 102 is specified at
only 55W FTC power limited to 0-8kHz with explanation
"The power bandwidth is limited due to the output Zobel
network". Continuous module power is listed in
datasheet as only 40W @ 25degC and 25W @ 50degC. Bel Canto
specified S300 and M300 amplifiers as 300W with the same
Icepower module (200ASC). These modules can produce
momentary power of 290W at 10% distortion and only at 230V
supply. Useless specification but 300W looks better than
200W on the paper.
Thanks Almarg for the feedback.
Thanks Kijanki for the feedback & some dope on how power supplies are spec'd. Lots of diff ways to specify a power supply & that adds to the confusion already prevalent in the audio community re. power amp output power, distortion & dynamic headroom.

Although for an 8 ohm load the OP's 525 comes surprisingly close to doing that, the 8 ohm ratings being 250 watts and 950 watts for stereo and bridged modes respectively.
Almarg, I might be reading this incorrectly but in reading the Pascal Audio S-PRO2 data sheet (link provided by Kijanki in an earlier post by him) I noted that the bridged mode (Pascal Audio calls this BTL mode) power output is 700W/ch in 4 & 8 Ohms using a 120VAC power supply. It's higher for a 230VAC power supply (that they use in Europe) - maybe the OP is using a 230VAC power supply?
Again, if I'm thinking of this correctly, in bridged mode this Pascal Audio amp module has quite a large output wattage that it can sustain given its 30A max limit. Some serious watts with current delivery to backup these watts....

I also noted that the max current from the integrated SMPS is 30A & if you read the amp specs, you will see that the max power is rated for a 2.7 Ohms load!! wow, this is the 1st time I'm seeing an amp manuf spec his amp for such a weird load. I did the math & voila what did I find?? At 2.7 Ohms load, the output current is 14.9A - exactly half of the 30A max. This made sense to me - 30A max, stereo amp module, therefore each channel gets 15A max. Hence the lowest load impedance it can drive is 2.7Ohms before the integrated SMPS runs out of current delivery capacity.
Thanks, Bombaywalla. I see what you're saying. The module datasheet shows that when it is operated with 120 VAC it is rated to deliver 600 watts into 2.7 ohms in stereo mode, although with just one channel driven. That corresponding to an output current of 14.9 amps.

While the max rating in bridged mode that you cited of 700W into 4 and 8 ohms corresponds, for 4 ohms, to 13.2 amps from each channel, simultaneously but with the channels being operated out of phase.

A couple of inconsistencies in the numbers, though, which I don't know how to reconcile:

1)The 950 watt figure I cited for bridged mode, for an 8 ohm load, comes from the Rowland site (click "specifications"). That number being even higher than the 900W number that is indicated in the module datasheet for 230 VAC operation, for an 8 ohm load in bridged mode.

2)I would think that the indication in the module data sheet of 30 amps peak output current is likely to refer to the peak of a sinusoidal waveform. (For example, I've seen credible indications that Pass Labs specifies peak output currents on that basis). While the currents that can be extrapolated from the power ratings based on Isquared x R would be rms values. For a sine wave, 30 amps peak of course corresponds to 30 x 0.707 = 21.2 amps.

As I say, I'm not sure how to reconcile all of that. Assuming that the module for which Kijanki provided the datasheet is truly the one used in the 525, I suppose it all adds up to further confirmation of how, as he indicated in his last post, power specs are often not defined on a consistent basis.

Best regards,
-- Al
Thanks, Almarg, for confirming what I was seeing. What prompted me to go to the data sheet was the power output inconsistency I read @ the Rowland website, your post & my initial quick perusal of the S-PRO2 data sheet.

agree that the 30A is max implying RMS = 21.2A, as you wrote. Then, in bridged mode if each amp in the stereo module is outputting 13.2Arms that total is 26.4Arms which is greater than the 21.1Arms that the integrated SMPS is capable of supplying!! So, is the amp really able to output 700W into 4 or 8 Ohms in bridged mode (as in the spec sheet)?
In bridged mode, the 13.2Arms must be the total bridged-mode current for *both* amps in the stereo module (700W, 4 Ohm load).
while in Stereo mode the current must be 5.5Arms from each amp (8 Ohm load, 245W/ch).
As you pull the amp out of bridged mode the speaker load doubles to 8 Ohms & the power output drops to 245W/ch.
Or, am i thinking of this incorrectly??

I agree - all these numbers don't jive with each other further adding to the confusion of what the amp is really capable of power output-wise. in such a case, I'd be inclined to take a slightly conservative path & side with the class-D amp module manuf...
03-10-15: Bombaywalla
Then, in bridged mode if each amp in the stereo module is outputting 13.2Arms that total is 26.4Arms which is greater than the 21.1Arms that the integrated SMPS is capable of supplying!! So, is the amp really able to output 700W into 4 or 8 Ohms in bridged mode (as in the spec sheet)?
I'm not 100% certain of this, but I believe the way to look at it is that since in bridged mode the two channels are operated out of phase with each other, and the load is connected between the two + output terminals of the amp, from the perspective of the power supply it is supplying 13.2 amps, not 26.4 amps, when supplying max rated power into 4 ohms in bridged mode.

In other words, the 13.2 amps that is flowing through one channel does not add to the 13.2 amps that is flowing through the other channel, because it is the same 13.2 amps!

While if both channels are driven in stereo mode the power supply would of course have to supply enough current to support the total amount of power being drawn from both channels. Note, though, that all of the output power ratings indicated in the module datasheet for stereo mode are based on only one channel being driven.
... all these numbers don't jive with each other further adding to the confusion of what the amp is really capable of power output-wise. in such a case, I'd be inclined to take a slightly conservative path & side with the class-D amp module manuf...
Agreed (except that strictly speaking I believe it would be "jibe," not "jive" :-)). Perhaps all that can be said with certainty is that this is a very powerful amp, but one which should not be expected to perform well when used in bridged mode with speakers having impedances which drop below 4 ohms at frequencies for which lots of power is likely to be required.

Best regards,
-- Al
Almarg,
I just want to reiterate how much you have helped. Simply moving bass traps solved my problem, that many people would simply blame on the electronics. You have indeed saved me from spending money on another JR 525 or a new preamp. I'm still listening to other DACs to see what improvements can be gained over my PS Audio Directstream DAC. Although I like bass, my priorities have always been what I consider a "natural sound", great spacing, and an open soundstage with good depth.
Glad I was able to help, Ricred, and thanks for the very nice acknowledgment. Enjoy!

Best regards,
-- Al
I moved the bass traps out of the room, put them stacked back in the corner, put two behind the listening position, with two in the front corners and after a whole day of listening decided that one in each front corner and two behind the listening position was best. No bass suckout, but more air and better imaging with two in the front(not stacked) and two in the rear.

Almarg- what is your thought on subs? I called PS Audio and they said I could control a sub through my Directstream DAC's RCA inputs, because my amp is connected via balanced cables. However their own literature says, not to connected both the RCA and balanced cables simultaneously. I want to try a JL F112, but don't want to purchase a preamp.
I'm uncertain as to how well connecting a sub to the DAC's RCA outputs would work. It would certainly function. But without clear information as to the design of the DAC's output circuits I would have some concern that doing so might have at least slight adverse effects on the signals provided to the Rowland amp, and thus to the main speakers, unless the circuits driving the two outputs are totally independent. That concern being heightened by the fact that as with the line-level inputs of most subs the input impedance of the F112's unbalanced inputs is low, in this case only 10K.

And I note that in the entire DAC manual the only statement that is bold-faced is "We do not recommend using both outputs at the same time."

And then of course there is the question of how good a match there would be between the sonics of the sub and the main speakers, about which I'm not in a position to comment.

Also, of course, there are other subs which provide speaker-level inputs, such as the RELs. However, the 525 amp is described as having "balanced topology implemented throughout all power and input/output circuits," which leads me to suspect that it may not be ok to connect the ground wire from such a sub to the amp's negative output terminal. And the amp does not appear to provide any other suitable ground connection point. In which case connecting that wire to a chassis screw on the amp would **probably** work ok, but again there is uncertainty.

Best regards,
-- Al