Back to Jeff Rowland, now listening to Criterion and 825 :-)

shakti

Well-Known Member
May 9, 2015
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Cologne, Germany
Shakti ,

How do these New Rowlands differ from say JR earlier stuff like model 9 et al ..
Difficult to say, as I have my former Model 9 Ti/HC not onside to make a direct comparison.


Coming from model 6, 8 and model 9 with battery PSU the more modern model 10 and 12 were already a step into the direction of a more "neutral" tonal signature. But Model 10 and 12 were still very close to the 6, 8, 9 range.
Than Jeff Rowland developed his first switch mode PSU and offered them as upgrade (or repair kits) for model 8, 9, 10, 12.

I had the chance to listen to model 8 and 10 in direct comparison to standard PSU and switch mode PSU.

The newer switch mode made the Rowland amps "faster" and more precise, but some start to miss the "soul" of the original sound.

The first steps with class D Amps, like model 201 and 501 were the next steps away from the old emotional midrange focussed Rowland signature to a more dynamic and neutral speaker amp.

I had not the chance to listen to models if the 300 series, as in Germany nearly not offered.

But listening to Model 625 and 725, the magic of the Rowland sound is back. It looks like, that someone has owed to Jeff a pair of model 9 and has given him the task to transfer the sound into a smaller chassis and to improve it as well.

Personally I see the 625 as the first real successor of model 6.

The current model 825 and 925 would be then the 2 (4) chassis replacement of model 8 and 9, which can be found in the chosen price point as well.

My model 825 reminds me to my former Model 8 and 9, but with more speaker control, more speed, more contour, but still with the typical "tone" of the Rowland DNA, which I like a lot.

Overall Rowland improved his goal to develop "silent" amps. The "blackness" in a full Jeff Rowland system is incomparable.

Listening to a system like the Avalon Osiris the track starts, that you enter the room of the recording, that the music starts.

This first seconds of "room" reproduction , before the music as such starts is something, which only a few systems can demo.

Interestingly Rowland managed over the years to transfer his DNA consistent into many different technologies in terms of the usage of different PSU or amplification modules.
 

GuidoCorona

Well-Known Member
Apr 23, 2010
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173
Summerville (SC)
Hello Shakti, a couple points...

* are you operating Criterion's battery power supply, or are you staying with its AC supply? If your AC mains were a bit dirty/grungy, Criterion's driven by batteries will enhance the overall listening experience, versus its operations driven by its integrated AC SMPS.

* PSU is actually a Rowland product name. PSU stands for Power Storage Unit... This is a external stand-alone power supply component based on ultra-capacitor technology that Rowland has developed specifically for -- and is compatible only with the Corus preamplifier, the Conductor phono stage, and the Aeris DAC.

* All, for some information on the Rowland M925, which is the native monoblock version of M825, you can have a look at my detailed scribblings at:

https://www.whatsbestforum.com/threads/rowland-m925-monoblock-amplifiers-break-in-notes.10653/

* The original M625 stereo and M725 monos have been succeeded a few years ago by the sonically enhanced M625 S2 stereo and M725 S2 monos. In turn, last month the M735 mono has replaced M725 S2. Reports this far have indicated that M735 is even much superior to its predecessor.

Regards, Guido
 
Last edited:

shakti

Well-Known Member
May 9, 2015
813
836
315
Cologne, Germany
* are you operating Criterion's battery power supply, or are you staying with its AC supply? If your AC mains were a bit dirty/grungy, Criterion's driven by batteries will enhance the overall listening experience, versus its operations driven by its integrated AC SMPS.

Mostly I am using the Criterion by AC supply. For dedicated listening sessions Battery Power is used. Both power solutions benefit from a solid PowerChord, then the difference becomes minor.



* PSU is actually a Rowland product name. PSU stands for Power Storage Unit... This is a external stand-alone power supply component based on ultra-capacitor technology that Rowland has developed specifically for -- and is compatible only with the Corus preamplifier, the Conductor phono stage, and the Aeris DAC.

Thank you for the explanation, PSU, LPS and others are universal abbreviations for external Power supplies, Jeff is doing a great marketing, but to brand an external PSU (Power supply unit) as "Power Storage Unit" " PSU" was not the best idea he had.

I heard the "PSU" once on Corus, was a great improvement, still like my battery supported Criterion "tone". The Thomas Holm developed Aeris DAC need a kind of S2 upgrade to work with High Res, currently not an alternative for me. Conductor is nice, but my current Cadence are in direct comparison not that bad, that I have to look for the upgrade.

* All, for some information on the Rowland M925, which is the native monoblock version of M825, you can have a look at my detailed scribblings at:

https://www.whatsbestforum.com/threads/rowland-m925-monoblock-amplifiers-break-in-notes.10653/


The M825 technical spec:

Output Power400 watts @ 8 ohms / 750 watts @ 4 ohmsFrequency Response5 Hz – 50 kHzInput Impedance40k ohmsTHD + Noise0.004%, 20 Hz – 20 kHzDamping Factor> 1000, 20 Hz – 20 kHzOverall GainSwitchable 26/32 dBInputs1 pr balanced (XLR) / 1 pr unbalanced RCAOutputs2 pr parallel binding postsAmplifier Weight160.4 lbs. / 73 kgOverall Amplifier Dimensions (h/w/d)16.5” x 15.5” x 16.25” / 419mm x 394mm x 413mm


and the M925 technical spec:

Output Power430 watts @ 8 ohms / 850 watts @ 4 ohmsFrequency Response5 Hz – 50 kHzInput Impedance40k ohmsTHD + Noise0.004%, 20 Hz – 20 kHzDamping Factor> 1000, 20 Hz – 20 kHzOverall GainSwitchable 26/32 dBInputs1 pr balanced (XLR) / 1 pr unbalanced (RCA)Outputs2 pr parallel binding posts (per channel)Amplifier Weight160.4 lbs. / 73 kg (per channel)Overall Amplifier Dimensions (h/w/d)16.5” x 15.5” x 16.25” / 394mm x 394mm x 413mm (each)


are nearly the same, so we can guess, that the M925 has the same 2 amplification Modules as M825 separated in 2 alloy cases plus separate Power supply units, which explains the slightly higher power measurable. As the Avalon Osiris needs a lot of power, I decided to go for 2 x M825, which is nearly doubling the power (compared to M925) plus the benefit of the BiAmping possibility.

On other speaker configurations, like single speaker wire input the M925 will be the better choice.


* The original M625 stereo and M725 monos have been succeeded a few years ago by the sonically enhanced M625 S2 stereo and M725 S2 monos. In turn, last month the M735 mono has replaced M725 S2. Reports this far have indicated that M735 is even much superior to its predecessor.

I found in the web, that Jeff Rowland has decided for a new generation of Lundahl input transformers for M735, even if the measurable seem to be not on the M725 level, the performance level was improved.

So let us wait, I would believe, that M835 and M935 will be the next upcoming upgrade ;-)

... but as M735 is still not launched on the JRDG URL, we might have to wait a little longer...
 
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GuidoCorona

Well-Known Member
Apr 23, 2010
327
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Summerville (SC)
Hello shakti...

Yes, I agree with you, the naming of the Rowland dedicated external power supply based on ultracapacitor to be PSU was not one of Jeff's best marketing decisions... Has apparently lead to some confusion as of the unique nature of the product.

You are also correct that an M825 stereo amp sports two power conversion modules in its audio chassis, while the M925 mono amp contains one module inside each of its two audio chassis. On the other hand, each M925 power supply chassis sports a 2500W DC power supply, while M825 shares the same 2500W power supply for the two stereo channels.

Rowland M735 has actually been released worldwide. Units have been shipped to dealers in USA, Europe, and Asia... It is unfortunate that the web site has not been updated yet.

The new Lundahl input transformers in M735 are based on amorphous (non-cristalline glass-like) Cobalt cores. The technology was first applied by Rowland as an option in the Conductor phono stage. Unlike in Conductor, the Cobalt transformers are standard inside M735.

As info on M735 is not yet on the Rowland site, I have compiled the following blurb about it:

...

The Rowland M735 stereo amp is rated at 330W per channel and is now shipping. The new amp has been enhanced over its predecessor in several areas with potential sonic performance relevance…

 Custom designed cobalt-based amorphous core input transformers are standard on M735. These are used instead of the older high permeability, mu metal lamination core type previously used in the M725 and m725 S2. Note that this is the first time that Rowland adopts Cobalt amorphous transformers in a power amp. Cobalt-based input transformers were first introduced by Rowland on its Conductor phono stage as a higher price option.


 Input phase filters have been enhanced to reduce further EM pollution.


 The error correction circuits first introduced in M625 S2 and M725 S2 have been enhanced in M735 to reduce distortion even further.


A new proprietary compliant material has been adopted for M735’s specially machined footers to maximize mechanical isolation.


You will find more detailed information on M735 in the official Rowland announcement letter below which I have saved on my Dropbox:

<https://www.dropbox.com/s/ohjhfx6zpobk8aa/Rowland M735 Monoblock Amplifier Announcement.pdf?dl=0>

The video below was shot by Lucien Pichette (Rowland Sales Director), and shows what the critter looks like:


<https://www.dropbox.com/s/gqrh9yxir927qbu/Rowland M735 Monoblock Amplifier Video.mp4?dl=0>

Needless to say, I hope the Rowland site will be updated soon!

Regards, Guido
 

shakti

Well-Known Member
May 9, 2015
813
836
315
Cologne, Germany
Since I am currently looking at various non-Jeff Rowland preamps (looking for the next step up) and not all of the proposed devices have multiple power amplifier outputs, I had to study the M825 manual intensively.

There is a switch on the rear of the M825,
which is simply called "link R to L".
Unfortunately, the text in the BDA doesn't give much more information.

Nothing can be found in the vastness of the net either. Since the M825 has input transformers,
I would be very interested to find out how the switch works or is connected internally

Currently my two M825s are connected with 4x 8m NBS Black Label cables, so that full biamping is operated from the pre-stage. One stereo power amplifier each drives one loudspeaker.

If you can't find anything useful in the BDA and on the Internet, I thought that such a switch would also cost money and that Jeff Rowland must have thought something about installing one.

Accordingly, I then disconnected one pair of the NBS Black Label XLR cables and set the switch to "on".

To my great pleasure, all 4 power amplifier stages continue to play, ie the signal that arrives from one XLR cable is transmitted to the other channel input.

The difference in sound is of course exciting, as it makes a big difference whether the signal is transmitted by 2 or 4 of these "thick" signal cables.

The difference in sound is very clear indeed. To my surprise, the variant with only one set of the signal cables played clearly more agile and lively.

Sometimes less just seems to be more, or Jeff Rowland seems to know his equipment so well that he has provided this switching option.

Now I have a spare set of 8m long NBS BL cables. So if I want to operate the Avalon Osiris with even more power amplifiers, nothing stands in the way ;-)
- at least the matching signal cables are already there ...

In any case, I can now look even more freely for preamps and am no longer bound by the fact that the Pre has to have two equal XLR outputs.

Let's see if I can find a Pre that plays even better,
than the Criterion shows me every day.

With my former Koda Takumi K10 I am a bit spoiled with regard to preamp ;-)

IMG_4594.jpg IMG_4595.jpg
 

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