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

**GuidoCorona** · 01-16-2011, 10:04 AM

Rhyno, one factor in the heat signature of M625 is the automatic self biasing of the device. For what I understand, as the average throughput rises, biasing moves more towards class A. On the other hand, idling power appears to be much lower, indicating that the biasing may readjust downward as well.

One more factor is the high compactness and circuit density of the device, hence the relatively higher heat dissipation per square inch. If the device were larger, skin temprature would be deceptively lower.... 100W idle consumption per the specs at:
http://jeffrowland.com/knowledgemana...questionid=585

Concerning long term reliability, we can hope that M625's behavior is similar to older high bias JRDG designs.... Anecdotally speaking, as far as I know, my former JRDG 7M monos are still making music without issues over 20 years since they left the factory.

Rhyno, do you live in Houston? ... So does David (Kawika). G

**Husk** · 01-16-2011, 08:23 PM

Kawika, I am not especially concerned with how hot the 625 is to the touch, but how much ambient heat it puts off in your room. What is like in your room after a few hours of listening? Do you leave it on 24 x 7?

**Husk** · 02-08-2011, 03:33 PM

GUIDO, I am hearing that the 925's are 4 to 8 months out. Not good news.

**GuidoCorona** · 02-08-2011, 04:51 PM

Husk, that is quite possible.... M925 may end up much more complex a project than a higher powered port of M625. in the meantime, I am considering an M625 to tie me over. I have reports that M625 was handling the Vienna Die Muzik at CES with very high synergy. G.

**Husk** · 02-12-2011, 05:12 PM

Guido, You are probably right. Jeff never releases anything until it is perfect. I believe they are also spending a lot of time and energy on their new dac.

**Orb** · 12-21-2011, 05:33 AM

Guido,
appreciate it may had been awhile since you listened to the M625, but can you remember how hot in terms of temperature the amp operates; did it seem warm-hot-etc?
Curious as it seems to have low mains consumption when idle (some kind sliding bias I assume), so wondering if this reflects lower operating temperature when idle, and also when it is in use.

Cheers
Orb

**GuidoCorona** · 12-21-2011, 07:13 AM

Hi Orb, yes M625 appears to have an automatic bias adjustment. As far as I know, it idles at approx 100W. During operations, the bias grows as needed. Skin temperature of the device seems identical on top/sides/front/back, and also depends on room temperature... Seems to range from medium warm to rather toasty, depending on duty cycle and room temperature.... Only during August, when my music loft sometimes reaches the mid/high 80s, M625 may become borderline too toasty to touch.

**Orb** · 12-21-2011, 07:55 AM

Good to know, thanks

Cheers
Orb

**GuidoCorona** · 12-23-2011, 07:04 PM

I called the JRDG factory today. The M725 monos have just been released and have started to ship. Price seems set at $28K for the pair. Production level units will be heard at CES in January. G.

**GuidoCorona** · 01-19-2013, 06:36 PM

Hey Husk, in case you were still interested, JRDG has just release the Model 925... Yes, the charming quad-chassis monoblock amp is shipping. I have just posted updated specs for M925 at:

http://www.whatsbestforum.com/showth...owland-925-amp