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Experiencing Rowland M925 4-chassis reference amps

My pair (or should I call it my quartet?!) of the new SS Rowland M925 reference mono amps were finally delivered yesterday.... Needless to say, I am excited!

The 430W M925 monoblock amplifier is a hefty affair: The amp is formed by four chassis: two power supply chassis and two audio chassis, amounting to a total weight of 380 Lbs in the four boxes, and 320 Lbs in their birthday suits. Each chassis is double boxed, protected by heavy urethane foam inserts, and then bagged in a heavy cloth sleeve tied with a drawstring.

Each power supply box also contains an accessory carton, featuring a power cord terminated at one end with a 20A IEC connector, a heavy ombilical to carry DC current to the audio chassis, and a skinnier ombelical, which I conjecture carries control signals and may have an additional grounding line. A baggie contains 3 1-inch spherical delrin footers that can be screwed into the divets at the bottom of the SMPS chassis if if you do not use 3rd party spikes/footers. A smaller baggie contains 4 smaller delrin beads... They fit into the dimples milled into the top of each the power supply chassis, and are used to keep top and lower chassy from touching when the two are stacked.

I am using Nordost Titanium Sort Kones instead of factory-provided footers. Each power supply chassis stands on top of 3 divet-centered Kones. The whole thing sits on top of 1.5 inch thick granite slabs, which have been patiently waiting in place for the M925 amps since 2011.

The audio chassis are even heavier... They will get into place in the next few days, one way or another. Rowland recommends the stacking be a two-person job.

In order to break-in both output terminal in each unit, I will connect each amp to my Vienna Die Muzik with a form of shotgun wiring: Aural Symphonics Chrono and Cardas Golden Ref for the time being. The Aural Symphonics speaker wire connects to the single 5-way binding post of the Muzik speaker with bananas; the Cardas Golden Ref connects to the same posts with spades... I have already tested the configuration using other mono amps... Works flawlessly. Of course, I have no idea if M925s benefit from shotgun wiring... This will be part of the discovery fun!

The amps will be fed by the Criterion linestage through Aural Symphonics Chrono B2 XLR ICs.

Power cords will be Aural Symphonics Magic Gem and Ultra Cube XXV, plugged into a dedicated 20A circuit served by Furutech outlets.

According to Jeff Rowland, breaking may be excruciatingly long, because of the oversized input transformers and power supply. I suspect that the process may extend well into the summer months... I will log my periodic observations on this thread.

For sake of completion, here are the amps specs as far as I know them:

Monoblock Power Amplifier OUTPUT POWER: 430 watts @ 8 ohms/850 watts @ 4 ohms
Monoblock Power supply: 2400 W regulated DC SMPS per channel, with Active Power Factor Correction (PFC).
FREQUENCY RESPONSE: 5 Hz - 50 kHz
INPUT IMPEDANCE: 40k ohms
THD + NOISE: 0.004%, 20 Hz- 20 kHz
OVERALL GAIN: Switchable 26/32 dB
Combined AMPLIFIER chassis & POWER SUPPLY chassis WEIGHT: 160.4 lb / 73 kg (per channel)
TOTAL DIMENSIONS (H/W/D): 16.5" x 15.5" x 16.25" (per channel) 419mm x 394mm x 413mm

Saluti, Guido
guidocorona
guidocorona OP
4,298 posts
 
All, besides waiting for Aeris, my next crucial step, which might take up to one year to finalize, will be to equip the system with a loom of wires, and possibly power management products, that maximize synergy with my speakers and Rowland electronics... and meet my goldilockian preference for evenly textured musicality and broad frequency coverage.

Based on my RMAF 2013 visit, and on prior experiments, I have narrowed my short list down to three fantastic product lines, which all bear further examination, listed below in totally random order...

* Nordost Valhalla 2 -- What a stunning surprise... In olden days I sometimes felt that the original Valhallas were a smidgin to slender and trebly inclined... But the new series that I auditioned in Blanca Peak is magnificently harmonically texttured, and is an incredible imager/stager, while maintaining the broad frequency extension
that the Nordost Valhalla line is well known for.

* Cardas Clear and Clear Beyond -- performed magnificently musical and resolving in all Rowland-based system that I heard at the show;

* Shunyata Z-Tron Anaconda and Pythons -- A long time love that is still going strong... I experienced their synergy with Rowland and Die Muzik in my own
system a couple of years ago.. No reason to believe that I would love Shunyata products any less today.

I am positive that any of the three series above would make for heavenly system-wide looms in their own special way... If you have experienced any of these products, do let me know your observations, comparative or not as they may be.

Saluti, Guido
krell888's avatar
krell888
12 posts
 
I am planning to upgrade my 625. Considering 725 but after reading about 925 from Guido, I am considering 825. I am using it to drive sonus faber Amati Anniversario
guidocorona OP
4,298 posts
 
Excellent choice Krell888... While M725 remains an exceedingly fine monoblock amplifier, I found M825 to outperform it.... More revealing than M725, and more musical at the same time.... And I fully expect a single M825 to deliver a larger stage and more authority than an M725 monoblock pair... M725 delivers 330W/8 with a 1200W DC power supply on each chassis... The M825 stereo delivers 400W/8 and 750W/4, and shares a 2500W DC supply for the two
channels.

There is also a direct growth path in M825 without loosing your investment... You will be able to add a second M825 chassis at a later time for even greater authority... A toggle switch in the back of M825 ties the left and right channels... This means that the two NCore NC1200 modules, would be processing the same input signal... You would connect one M825 output channel to the lower binding posts of an Amati Anniversario, and the other output channel to the upper binding posts of the same speaker. You would then connect the second M825 the same way to the other speaker.

Best, Guido
krell888's avatar
krell888
12 posts
 
Thanks Guido for your enlightening advise. Some years back, before I purchased the m625, I was using the M8 which was excellent until the point I found M625. I auditioned the Ice powered amps I din enjoyed it as the presentation was too clean and lacked the musicality. Just like CD and LP, the latter sounds more musical. Assuming the Ncore is superior over the traditional A/B output, the stereo block M825 has crosstalk and inter modulation distortion because both channels are sharing the same DC supply and in the same chasis unlike in a monoblock. Don't know whether the SMPS powers supply would have crosstalk distortion. Amati speakers have only one level of input and I presumed biamping is not possible. The M825 certainly looks more juicy and beefy and sophisticated looking from the rear end and my visual perception intuition tells me that M825 is the way to go however, my past experience of class d Jeff amps including the feedback from users of class d amps in the various forums and the crosstalk thing affects me in making a decision as to which is the right and better amp. Am I right to say that I won't be getting so much of a difference if I upgrade from m625 to m725 rather than to M825?
krell888's avatar
krell888
12 posts
 
Morning Guido

The frequency response of the 825 is 5hz - 50kHz compared to the 725 which has significantly higher range (5Hz-350kHz). What this means to the music playback? Is 50kHz sufficient? If not the 725 may be a better pick.

The damping factor for the 625 comparing to most other class a/ab amps is relatively high except comparing with class d amps which have very high damping factor. Was told that a higher damping factor would be good to tone down speakers that are too bassy. But how much do u need actually. Maybe 200 is more than enough. Arc tube amps have damping factor less than 50! I noticed that Jeff does not specify the slew rate of his current models exept in the past. Don't know why as slew rate is an indication of fastness.

I m also concerned that class d technology for audiophile amplifiers is at its evolution stage while class a/ab amps are now at the peak and plateau. That means one could say that there will be better class d amps to come, whereas the 625 is already at its best in its class. Its difficult to accept that a class d amp in its evolution stage is already better than the class ab amp in its plateau stage of development.

I want to believe that 825 is a better choice than 725 but I m still struggling to leave the old school of thought that a/ab is the safer choice as the development is at its mature state,

Hope you can sway me more to accept 825. Please. 😄. Thanks

Bernard
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