OTL Amps and ProAc Speakers

Does anyone have any experience with OTL amplifiers (specifically a Graaf GM20) driving Pro Ac 1SC monitors? Thinking about switching out my Audio Research VT-50 for the OTL route. Any OTL advice would be greatly appreciated.
I haven't had any experience with that particular combo ,but with an Atmosphere M60 and Proac 3.5.I was amazed how dynamic and still very musical ,a match nearing heanen.There's magic in those OTLs provided the load is fairly simple/not a complex crossover.Good luck!
Hello JLA- I have a GM20, though a special European version. Though OTLs usually prefer higher impedance speakers with at least moderate efficiency, my GM20 is amazing on my 4 ohm Venture speakers. It seems much more powerful than my 50W SET amps. The only consideration with the GM20 is that it has a lot of gain which can be great if you're using a passive or low gain active preamp. The only issue with the 1SC would be trying to overdrive them with alot of deep bass. I've heard the 1SC bottom out when driven hard. Other than that, it should be a great combination. Good luck.
I have owned/own a couple OTL amps, Atma-sphere M60,s and I currently own the Tenor's and I also own a pair of the 1sc's. The OTL's are a fine match. The proac has a fairly flat impedence curve and the OTL's like this. While I don't have specific experience with the Graff I think it is a safe bet to sound good.
Thanks a lot you guys for all the great info! I am looking forward to entering the OTL space...should be fun.
Jcbtubes...Thanks for letting me know about the gain on the GM20. I would be running a Wadia 860X directly to the GM20 and would assume that I would be okay since the gain can be set appropriately inside the Wadia. Do you have any experience running your GM20 in this type of config? Thanks again...John
Judging from my own experience I think many here would really appreciate serious performance gains by using a product called the ZERO autoformer. Information regarding these is available at http://www.condor-connection.org/asog/tweaks/ps/zero/index.html

I use Atma-Sphere M60 amps, and my speakers are N.E.A.R. 50Me II's. They have a nominal impedance of 8 ohms and I am told they do not dip below 6.5 ohms. It was amazing how much the ZERO's improved the performance in my system. They were a MAJOR upgrade. I have the autoformers connected directly from my amps to my speakers, bypassing speaker cables entirely.

Another product in my system I highly recommend is Walker Audio High Definition Links Mk. II. If you try these out be sure to get the Mk. II version.

It is phenomenal how much congestion was removed with these products, especially the ZERO's. I can not imagine anyone being disappointed with either.
I switched from a McIntosh MC2205 amp (solid state, 200wpc) to the GM20 to go with my old (14 years) pair of ProAc Studio-2 speakers -- man what a difference, the speakers just came alive. I did listen to the 1SC but not with any tube gear, so I can't say. The SC1s seemed to be very focused and has a much smaller soundstage than my old studio-2s. But the studio-2s are about twice the size of the SC1s. I also own Graaf's 13.B tube preamp but I find that the lowend noise is better when GM20 is paired up a SS preamp such as a McIntosh C32.
Hello again, Jla- I'm certain that the Wadia straight in would work fine as long as the interconnects are kept relatively short. The question of pre-amp or not to pre-amp has been asked and answered many times here. There certainly is "cleanliness" usually found with no additional active stages. However, with a great pre-amp, the sound can be almost supercharged - not as clean or pure, but with better drive and authority. You'll have to find out for yourself which camp you prefer to be in. Trust your ears and listen for the emotional connection to the music, not just for detail. Good luck.