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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

Showing 10 responses by krell888

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
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
krell888's avatar
krell888
12 posts
 
Guido, you are simply the best. I am placing the order for that beefy 825. Will update about the sound some time later. Dealer here in Singapore told me, Jeff is struggling to meet demands as he personnaly checks every piece that goes out the factory. Waiting time could be awhile.
krell888's avatar
krell888
12 posts
 
Hi Guido, did you ever wonder why, the heat dissipators or sinks of current amps are so huge? The size of the dissipators take almost half the width of the amp unlike the old amps like models 8 and 9 where the the dissipators are relatively smaller than the overall width of the amps. The fact that the m825 and m925 emit lesser heat because their output stage is Class D, they actually do not require dissipators as large as m625 or m725 in terms of the ration of the width of heat dissipators over the overall width. The reason I am asking this is was it because they want them to look beefy rather than functional?

Bernard
krell888's avatar
krell888
12 posts
 
Thanks Guido. Btw, how is the sound of this Jeff reference compare to class A classics like Gryphon Antileon and the newer Gryphon Memphisto. I heard the Vitus and I am not for it. So are the Plinius which are also Class A design but does not sound as musical as the Jeff class AB design of M625. If there is any amp out there that can give Jeff's newest design a challenge, it must be the Gryphon as these are truly class A. If so, then one could say, class A design still rules the pantheon. If not, then Class D has finally arrive at the pantheon to replace Class A.
krell888's avatar
krell888
12 posts
 
Hi Guidoo

I was so excited to receive the 825 last Thursday. Setting up took quite awhile as a large effort was made to put this monster into the Finite Elemente Pagode Aps rack as the space just only fit the monster. After playing for 2 hours I realized the potential of what it can do to my sonus faber Amati Anniversario. It presents a bigger soundstage better imaging and detail except that its raw and lack the finesse as compared to my previous 625. The bass was already better than 625. This is without doubt as the 825 packs with much more power. However, the next day when I switched the amp on again, i heard a loud crank sound inside the chassis and thereafter there was no sound coming out from the speaker. Yes no signal. Following day, the dealer took it back promising to replace a new one. This happening prompted me to learn more about class d amp. I saw this website below and read it had to say. I m particular concern that it said that the switch mode power supply is so complex that if it stay on operating pass 7 years, then you are lucky. More often than not it wouldn't survive pass the 7 year mark. What it is trying to say is that the reliability is limited in a switch mode power supply and that it virtually can't be repaired AT ALL. What's your take on this?

http://education.lenardaudio.com/en/12_amps_6.html
krell888's avatar
krell888
12 posts
 
Found out that a condenser (capacitor) swelled and that it also emits a smell when the cover was opened on the main unit (not the power supply). The power supply unit was alright.
krell888's avatar
krell888
12 posts
 
Finally the replacement of my 825 arrived. Was told by the local agent that Jeff made some modification to prevent the capacitor from giving way in the future. It was sheer joy just looking at the 825. It's beauty second to none. After about 4 hours of listening, I can't say much about it. Only that it sounds bigger and larger than my previous 625. Vocal now sounds more prominent and the tonality sounds sweeter. Overall it still doesn't sound warm and bloom as my well run in 625. Btw, just got the Aeris. Sounds excellent. Never mind about it can't play DSD files or upsample PCM more than 192khz. It just play more of my CDs musically. It's holographic, detail without sounding clinical but organically pleasing.
krell888's avatar
krell888
12 posts
 
It's ashamed. The amp blew again after 10days. When it arrived, I have it switched it on for 9 days even without playing and it was alright and did fine. The sound was promising as times but some times it went into a mood swing. This I presumed is normal as it needed to run in as Guido has described. But even then, I was enjoying playing symphony pieces thru the vinyl like Handel's Watermusick. It plays the symphony music very well. Handles the crescendos superbly and piano notes and violin sounded so real and natural. Yes the highs, the crispness and the abilities to separate percussion highs from electric guitars, etc, essentially able to create a sense of space between instruments were fantastic. Soundstage, though already better than my 625, is still evolving. In fact in all aspects, the sound is still evolving. Only one area that the 825 has not yet come to match the 625, is the female vocal. Linda Ronstald tracks in the album, Simple Dreams has not sounded as sweet and warm compared to 625 but then it's jusr 30 hours of playing. The 825 plays bass excellently and has a tight grip on the woofers of my sonus Faber amati Anniversario. It fully controls and plays the Amati to the fullest never once I suspect it doesn't have the power and grip. This I realized when playing Carl Orff's Carmina Burama Paul Hindernith: Symphonic Metamorphosis, Robert Shaw The Atlanta Symphony Orchestra and Chorus. For all I knew over the short time I had with the amp, I was confident that the amp will show up its best (no doubt) later when fully burnt in. On the tenth 10, I switched it off in the morning and on the evening I switched in on and played for an hour or so before I switched it off to switch the gain from 32db to 27db. After selecting the gain, I switched on the amp again and heard that eerie, "clung" sound again inside the amp. I knew it.

I called my dealer immediately and they got a reply from Jeff that it would be replaced as soon as possible ..... With a 725 without topping up. The 725 now cost USD800 more than and the 825 now. Yes, I reckon I am fated with class A/B and had no luck with 825. Will upgrade to 925 in future. No worries.
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