Jeff Rowland

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