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Jeff Rowland Design Group

I want to say a good word for JRDG customer service. I own a consonance preamp that is now 26 years old. An absolutely wonderful preamp. Early one morning during a "late night" listening session I made a boneheaded move and while adjusting the line level gain, put that module back in the preamp one pin off. That module became toast as soon as I turned it back on. Duh. The following Monday morning I called JRDG and to my surprise was able to talk to Jeff himself. He looked in his inventory & was able to find another module for the consonance (a 26 year old preamp!) of which I bought instantly. It was shipped out that day & I bought another fuse to put in the preamp itself. Long story short, I couldn't get it to not blow a fuse instantly when powered up, so prior to putting in the new module, asked Jeff if the new module would fix that issue. He said the module would not fix that, so I packed the whole thing up & sent it to him for repair before messing it up any further myself. He received that preamp on a Friday & the following Monday his secretary called me and stated he had it fixed.There was an issue with the power supply (as well as the toasted line module). I received it today & it sounds better than ever. Again, mind you this is a 26 year old preamp that he apparently made a priority of to fix. The new upgraded module & power supply cost a few hundred dollars and his labor charge to check this preamp out & fix it, was minimal. He certainly wasn't prompted by financial gain to fix my mistake, much less make it a priority. That my audiophile friends is great customer service.  
boxer12
georgehifi's avatar
georgehifi
10,312 posts
 
Take your pick, these designers below they will have something.
But for your speakers, I’m told they closely follow the impedance and negative phase angle of the PL300’s, and these speakers are not a very demanding load. worst is 4ohms from 70hz to 200hz. Even mosfet will do.(Pass) https://www.stereophile.com/images/1016MA300fig1.jpg

But I have a feeling this is a loaded question, to which you won’t be convinced, no matter who says what.


These designers are to me are still at the pinnacle of hi end amp design, and still use linear amps and linear power supplies for their "flagship amps".
Flemming E. Rasmussen Gryphon
Dan D’agostino Krell and D’agostino.
Nelson Pass Pass Labs PassDiy, Threshold
John Curl, Halo and other hiend old school Parrasounds
Jeff Rowland Design Group non class-d old school
Mark Levinson non Class-d
ect ect.

Cheers George
ricred1
2,005 posts
 
George,

It isn't a loaded question, but you are correct that I'll never be convinced by what people say for a couple of reasons. For one I honestly think so many people make comments about components that they never actually heard. Secondly, there are no absolutes in audio, only preferences; therefore it isn't what someone says, it's what our ears hear that makes the difference. I don't think what I have is the best, not even close. I set a price range for what I want to spend on each component and try to evaluate it in my own system. If I end-up preferring something else, I have no problem saying I prefer something else. 
georgehifi's avatar
georgehifi
10,312 posts
 
It isn’t a loaded question, but you are correct that I’ll never be convinced by what people say for a couple of reasons.

" Please recommend an amp to replace my 625 S2."
OK, if it wasn’t loaded, you ask for my opinion on what would be good, I gave you the designers on where to look, I think your capable to choose a Linear amp with linear power supply from one of these designers, that would easily out perform the 652’s for sound quality.
The 625 S2 could have been much more if they used linear power supply instead of smp.

Independent bench tests carried out:
" The 1-watt signal-to-noise ratios measured by Newport Test Labs fell quite a bit short of JRDG’s specification of 95dB, with the lab reporting figures of 80dB unweighted and 88dB A-weighted referenced to one watt.
I suspect that the signal-to-noise measurement could have been tainted by very high frequency noise generated by the 625 S2’s switch-mode power supply"

Cheers George
imhififan's avatar
imhififan
2,181 posts
 
Measurements :

Dan D’Agostino Momentum monoblock power amplifier

The unweighted, wideband signal/noise ratio, ref. 2.83V into 8 ohms and taken with the input shorted, was a good 77.2dB, this improving to 78.1dB when the measurement was restricted to the audioband. Switching an A-weighting filter into circuit improved the S/N ratio to 81.65dB.Read more at https://www.stereophile.com/content/dan-dagostino-momentum-monoblock-power-amplifier-measurements#7q...


Dan D’Agostino Progression Mono monoblock power amplifier


Measured with the input shorted to ground, the Progression offered a wideband, unweighted signal/noise ratio of 57.5dB, ref. 1W into 8 ohms. This was primarily due to the presence of noise with a center frequency of 923kHz. Concerned that the amplifier was picking up some RF interference that was being demodulated, I turned off all the CFC and LED lights in my test lab, but the noise persisted. The ratio improved to 80.1dB when the measurement bandwidth was restricted to 22Hz–22kHz, and to 87dB when the reading was A-weighted.
Read more at https://www.stereophile.com/content/dan-dagostino-progression-mono-monoblock-power-amplifier-measure...

Parasound Halo JC 1 monoblock power amplifier

The JC 1’s unweighted, wideband signal/noise ratio (ref. 1W into 8 ohms) was good at 73.3dB, this improving to 87.8dB when the figure was A-weighted.
Read more at https://www.stereophile.com/content/parasound-halo-jc-1-monoblock-power-amplifier-measurements#upUeY...

Pass Laboratories XA200.8 monoblock power amplifier

The unweighted, wideband signal/noise ratio, ref. 1W into 8 ohms and taken with the input shorted to ground, was an excellent 83dB. This improved to 88.2dB when the measurement bandwidth was restricted to the audioband—and was even better, at 92.1dB, when the measurement was A-weighted.
Read more at https://www.stereophile.com/content/pass-laboratories-xa2008-monoblock-power-amplifier-measurements#...

Jeff Rowland design 625 s2 stereo Power Amplifier

the lab reporting figures of 80dB unweighted and 88dB A-weighted referenced to one watt.
Read more at https://i.nextmedia.com.au/Assets/20170221014711_jeff_rowland_685_s2_power_amplifier_review_test_lor...

Look like the Jeff Rowland S/N ratio is better than Dan D’Agostino and Parasound
ricred1
2,005 posts
 
imhififan,

I’m not a technical person; therefore I didn’t know how the JR 625 S2 measured. I think some believe "audiophiles" select components in a vacuum. I listened to several amplifiers below $20K in my system and based on listening I prefer the 625 S2. I’ve owned several amplifiers prior to the 625 S2, including Parasound. It’s impossible to listen to every amplifier that exists, but I did compare it to a couple amplifiers that many say sound great. I’m still mystified that people are quick to talk bad about components that by all indication they never heard. I don’t talk about or provide advice about any component unless I’ve actually heard it...preferably in my own system.
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