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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
 
At 20 hours, the stage has a nice depth to it.... In addition, resolution is intriguing. Yes, I am discovering some of my CDs anew... if sometimes in unusual ways: I have a set of Bach Well Tempered Klavier played on harpsichord; and I had never realized that there some cute errors in the performance... Not wrong notes per se, but errors in timing between the two hands, and some rhythmic imperfections. Until M925, such minutiae were blended into the background.

I had a little "excitement" yesterday: I had a friend over to help me with the chassis stacking operation... Yes, it is a breeze with two people. However, when I powered up the right amp, the right speaker started to emit a bizarre multi-frequency burr, as if I had a mad cicada in rut inside the coaxial flat driver... And no music signal could be heard at all from that side... Disconnected and reconnected the whole amp to no avail.... The factory assured me that I must have done something wrong with my connections. True enough: I eventually discovered that the source selector switch was inadvertently flipped upward to RCA mode. Flipped the switch back to XLR balanced and reconnected... The amp started to work again without further ado.

But with hour 21, the amps have decided it is high time to go into a bit of break-in funk. Image is more recessed and has lost some airiness. The voice of Mezzo-soprano D'Althan in Exulta Filia by Claudio Monteverdy has developed a bit of a steely burr on the sostenuti at end of phrases, where the incompetent recording engineer is fooling around with artificial reverb to enhance the echo of the small church used as recording venue.

Now I have inserted a tuner into the system, so to exercise the amps 24/7... Nighttime the amps will be served a diet of FM interstation hash.... Extremely healthy and highly decongesting!

G.
guidocorona OP
4,298 posts
 
At about 100 hours of operations, and an additional 45 hours on standby with the linestage feeding FM hash from the tuner into the M925's input transformers, here is a very brief update

Thankfully the rather jarring steeliness in the resonance notes that I earlier reported on the young mezzo soprano Tania D’Althann in Monteverdi’s Exulta Filia Sion (Girlande Sacre, Ghirlande Profane Arts Music redbook) has been already reabsorbed by about 75%... She does sound significantly more natural than a few days ago. The other side of the coin is that minor blemishes in her intonation, breathing, and rythmic technique, which I had not noticed with my previous amps, are gradually coming to light with M925's low level resolution.

G.
vicdamone
850 posts
 
A wonderful account, thanks for taking the time.
french_fries
815 posts
 
(Just kidding around), but at FIRST you expressed concern that voices sounded steely while the amps were breaking in, and NOW your concern is that due to the improvement in transparency that the amps produce, voices sound flawed due to the limitations of the singer(s). Perhaps a downgrade in the future would be something to consider if this becomes increasingly bothersome...
guidocorona OP
4,298 posts
 
Hahaha David... You may have a point! To put things into perspective, we are talking here about a very young Tania D'Althann, probably in her late teens or early twenties, on a work with melodic embelishments which are devilishly difficult to render with precision... I do not fault D'Althann for the minor issues... Nor of course the M925 for evidencing them. My only beef is with the recording engineer who took undue liberties with his console, and monkeied around with the reverb pot, just to enhance what D'althann was already masterful on her very own.

If I remember correctly, the CD is copyrighted 1982, but might have been recorded as early as 1978, perhaps a time where recording engineering flights of fancy would be masked by most sound reproduction equipment.

It is interesting that the engineer appears to have lavished his disruptive attentions on D'Althann, because the voice of countertenor Giuseppe Zambon, who uses the same approximate voice range for his selections, is unaffected, and always sounds completely natural.

On a happier note, at approximately 120 hours, the sweetening of the residual steeliness is detectable only in traces, while the singer's image has continued to solidify.

Saluti, G.

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