Rowland M625 class A/B 300W Stereo Stereo Power Amplifier

[Miro Krajnc]

Hello everyone,

recently, I have listened to the Rowland 625 in a system with an Pass active crossover:

turntable: Puhar / ESE Lab, Panasonic Strain Gauge
Combak Remiyo CDP 777
Joule Electra JE-450ME, preamp
Pass Labs XVR-1, electronic crossover
Rowland 625 for the ribbons
2 x Spectron, Musician III SE Mk II, upgraded with V-Cap in Bybee filters for the woofers
SoulSonic Impulse speakers

We also have had Krell 2025e on hand, but the real star was the Rowland 625, either used as a mid/tweeter amp, or a woofer amp. This amp really excels across the whole spectrum.
The owner now seeks a second hand 625 .
Cheers,
miro

 

[GuidoCorona]

Hi Miro, how are you planning to apply a second M625 to the system? In a vertical biamping configuration, or instead bridging both M625 to mono operations (not officially supported)?

If you are thinking of bridging, a better solution might be to use a pair of M725 monos instead... M725 sounds even more refined than M625, because it features ceramic mother-boards throughout, and 4-poles Jensen capacitors in the power supply rectification.

If you decide for a 2nd used M625 instead, make sure it is an updated unit. If you supply its serial number to the factory, they will be able to tell you. If the unit were a non updated original production run, it can be easily updated by the factory to the current circuit standard.
Guido

 

[Miro Krajnc]

Hi Guido,
absolutely in vertical configuration as I would like to keep the back EMF from influencing each other.

In my humble opinion bridging is not the way to go, especially if the power supply isn`t up to the task. Most of the amps sound less than optimal in the bridged configuration and for various reasons (mostly they sag under the heavy load), at least to my ears. I prefer more transistors and no bridge.

Updated unit? This is new to me, thank you very much for this info I will pass it on to the owner. The 625 itself is probably the most interesting AB class amp I have heard in a long time.
May I ask what the update consists of?

Thanks,
miro

 

[GuidoCorona]

Hi Miro, I concur with you about user-initiated bridging... If the manufacturer has not provided an explicity bridging switch or methodology, he has probably good reasons to abstain.

Concerning the M625 update... I have not learned what it consists, but I suspect it may be trickle-down technology solution from M725 monos, which were developed after M625. I know that the procedure may be relatively straight forward. According to Rowland, the update to the very initial production run yields a perceivable sonic enhancement, but I have no further details. I vaguely remember that at one time the update may have been no charge or was performed for a nominal charge... In case you asked, there is only one update to early M625s... No further updates have been made to the internals since the first one.

 

[Miro Krajnc]

Hi Guido, thank you for your quick reply, but what I meant was actually that I`m pretty much against any type of bridge configuration, be it user initiated or original, provided by the manufacturer. If higher power is needed, I prefer more transistors and bigger power supply than bridging an amp. Bridge mode is a cheap way to gain electrical power and doesn`t always mean more dBW.
It can give more SPL, but not necessarily more micro and macro dynamics, if you know what I mean?

Another thing I don`t like is when an amp is running on high voltage which gives high power into 8 oHm loads, but not enough into 4 oHms. Spectron is one such amp (600W into 8oHms, 800W into 4oHms), while Rowland 625 on the other hand doubles into lower impedances. If I`m not mistaken the German magazine measured 300W/8oHms and 592/4oHms, which is much better behaviour and gives enhanced dynamics. Spectron has nominally double the electrical power, but sounds weaker, subjectively.

OK, we will have to contact Rowland in regard to the update. Thank you for pointing that out.
miro

 

[GuidoCorona]

Very interesting, the factory has published a more conservative M625 4 Ohms power rating of only 550W. Would love to find the article you mention... Is the German article available online? Post the Url if you can, or let us know the print publication, and issue number.

Best, Guido

 

[Miro Krajnc]

hifi & records 1/2012

http://www.i-fidelity.net/news/deta...ords-12012-ab-heute-am-kiosk-erhaeltlich.html

Jeff Rowland 625
Nennleistung 8 oHm (1%THD) 300 W
Nennleistung 4 oHm (1%THD) 592 W
Verstärkungsfaktor 21,2 fach / 26,5 dB
Klirrfaktor (THD+N, 10W/4 oHm) 0.012%
IM-Verzerrungen (SMPTE, 5W/4 oHm) 0,058%
IM-Verzerrungen (CCIF. 5W/4Q) 0.024%
Fremdspannung (20/250kHz-Filter) - 89,3/69,7dB
Geräuschspannung (A bewertet) -104,5 dB
Kanaldifferenz 0,01 dB
Empfindlichkeit (Vollaussteuerung 4 oHm) 2,3 V
Eingangswiderstand 9,4 kß
DC-AusgangsOffset 3,1 mV
Leerlauf-Leistungsaufnahme 90 W

Cheers,
miro

 

[GuidoCorona]

Thank you Miro, link and quoted info very much appreciated. Guido

 

[Miro Krajnc]

Just a brief update, the owner (Boris Vidmar) has found another Rowland 625 in Germany and now has completed the system. Jeff Rowland was kind enough to point out that these amps need more space for cooling purposes, so the current placement is just temporary. I have sent the serials to Mr. Rowland to see if the amps were already upgraded or not and am awaiting the answer.
I will hear this combination on May, 25th, when I will visit the owner, but he is already extremely satisfied with the sound. Will keep you posted.

Cheers,
miro

 

[GuidoCorona]

Hi Miro, have you found out if the two M625 amps require the factory update?

Saluti, Guido

 

[Miro Krajnc]

Hi Guido, what an interesting coincidence, this morning I have also received a reply from Jeff Rowland (I have sent him the serial numbers) and he wrote that their records do not show these two amps as being modified and that we should send the photos of the circuit board under the top covers, because some units were modified in the field.

We need to get the US standard Allen key to be able to open them up.

On a side note, this saturday I will visit the owner and experience the sound of two Rowlands singing in unison
Will keep you posted.

Cheers,
miro

 

[Miro Krajnc]

Yesterday I have heard the two Rowland 625 models in action and must say was mightily impressed. I wonder what the mods could bring though. Has anyone had any experience with the pre and post modificated 625?

Cheers,
miro

 

[GuidoCorona]

Hi Miro, My only experience with M625 is with the original version. According to Jeff Rowland, the update brings the M625 closer to the M725 sound... Having used M725 for about one hear (retired them last Friday to make room for M925), I suspect that this means that the update makes M625 even more transparent and resolving.... But I do admit of having no first hand experience of the change.

Guido

 

[Miro Krajnc]

Hi Guido, thanks, this is very good news, I just wonder if the mods could be performed at an authorized dealer`s place? Anyway, with these amps Jeff Rowland is absolutely on the right path.

Cheers,
miro

 

[GuidoCorona]

Hi Miro, I would not be surprised if the M625 update could be performed by a qualified national distributor... But the only way to find out for sure would be for you to contact the Rowland factory and ask them directly.

Alternatively, you may want to contact your Rowland distributor. Rowland distributors in Europe are listed at:

http://jeffrowlandgroup.com/us/distribution-europe.html

Guido