Question for First Sound Owners

I am using the H2o Signature Monoblocks with the First Sound Presence Deluxe Mk II and am very pleased with the synergy. There is a review of the amps on http://www.6moons.com if the amp is of interest to you...

I'm using the First Sound with a Music Reference RM-200 tube amplifier with excellent results. I feared the low input impedance of the RM-200 (15kOhm) would be a problem, but it sounds great to me driving Hot Rod Shearwaters.

Thanks guys for all your help. Cheers.

Just one more idea that hasn't yet been mentioned which is to check the input impedance on the CJ amp . . . The output impedance of the FS is rather high and if my memory is correct it is about 1700 ohms. So using a rule of thumb between preamp output impedance and amp input impedance of 50:1 or even better yet 100:1 then your CJ input impedance would need to be 85K or 170K respectively.

I have used VTL ST-150 with an input impedance of 100K ohms and currently an Art Audio PX25 amp with great results.

usually, if the input impedance of the next stage/piece of gear is 10X the output impedance of the previous stage/piece of gear, it is sufficient. So, if the CJ amp has about 20K Ohms input impedance, it *should* be OK in that it should not load down the preamp o/p stage.
The reason for the lifeless sound for the FS-CJ combination could have been something else besides impedance mismatch.
Eps, your orig post has no text supporting an impedance mis-match - you merely state that it's likely a mismatch issue. How did you conclude it was an impedance mis-match?