AR Ref 600s Best for Genesis2?

Sorry to change the subject, but has anyone compared the sound of the ARC amps before and after the new JFET input upgrade? I'm particularly interested in how the input change affects the timbre of the sound.

Jonathan, thanks for your very informative post. Otherwise, I may get the bad idea of owning the REF 600. I understand you have the BAT VK 150SE. How do they compare to other tube amps at or around the same price bracket?
Suchart

fwiw.. i have to completely disagree with Jtinn, specifically the statement: "thin sounding, tonally inaccurate, hotter than a radiator with bloated bass as
well as a huge noisefloor". that is a total bunch of concocted rubbish. my close friend owns Genesis 201's, and he tried a plethora of expensive amps to find the best for the mid/tweet panels. among those in his home audition were the VTL Wotans, ARC Reference 600 mkII, and the ARC Reference 300 mkII's. First we tried the Wotans.. while they sounded pretty good, they had a recessed midrange, which with the 201's midrange ribbon, was not good at all. then we tried the Reference 300's.. wow! these sounded great with the panels. Then we tried the Ref 600's. This was rather interesting. While the Ref 300's sounded a bit better in producing "bloom", they were actually slower during transcient attacks through the Gen ribbon's. We concluded that the larger capacitor power reserve in the 600's controlled the mid/tweet panels in the Gen's much better than the 300's. As far as tonality, the Ref 300's had a slight improvement over the Ref 600's.. I would attribute that to the newly designed JFET/6H30 input stage,
but neither amps had any tonal "anomalies". We also noticed that the 600's ran fairly cool with the easy to drive mid/tweet panel load. We were able to turn the fans down with the variable control because the tube output heat wasn't that bad with the panels. in the end my friend and i both agreed that for the genesis 201's the Ref 600's controlled the panels with better authority and accuracy than the Ref 300's.. and with the fans turned down the heat was a moot issue.. Good luck in your search!

I agree with the last response. Its difficult to find fault with the 600s. Certaintly, major crtitisms are unfair and inaccurate. No amplifier handles transients on orchestral passages as the 600s. There is no mid-bass bloat, unless one is mistaking deep controlled bass for bloat. Deep bass is a good thing. Tonally inaccurate is so wide of the mark there's not much to say. The tone is realistic and accurate, but not colored and euphonic as many tube amps. The Bat Amp is far less tonally accurate. I also think there is no such thing as too much control. You get what your willing to pay for and all else masks hidden desires or agendas.

May be I jumped to the conclusion too soon about the Ref 600s. But I must defend that the Bats are very suitable for the Genesis as well. In terms of sound quality, I regard the Bat as detailed, fast, and musical. With four monoblocks they can control the Genesis just fine, giving up only at the very loud level. I have no doubt about the power and control of the Ref600s but don't want to give up the blooming quality the Bats have in abundant. Now I decided to stick with Bats but will either add another 2 monoblocks of VK60s which is a cheaper alternative or switching to four monoblocks of Vk150s.