Music Reference RM-200

Thanks for the help and clarification. I thought both versions were rated class A. This other person thinks that it's only the mk2 version and he thinks I'm intentionally misleading. I'm sure they sound different but that doesn't mean they both are not great amps. Some times designers change the model for a different audience who uses different kinds of speakers or that they just want to try something new and experiment. At first, I did not like the mk1 model but then I spent more time with it and realized how good it was with the tone and timbre of instruments, as well as the balance of other qualities throughout the frequency spectrum. I wish it did have a little more damped bass, but everything has tradeoffs. I will call Ram Labs about the tube swap because I know that they are used in these amps in unique ways. 

Does anyone have suggestions for a good balanced tube preamp?  

I've used an Atma-Sphere MP-3 with the RM-200. Both units are fully differential from input to output which is an added benefit. I really don't know of another preamp that is fully balanced like the MP-3 but others might have recommendations there. However, there are plenty that offer balanced outputs which is not quite the same.

As for the tube swap I'm trying to save you that phone call because you'll be speaking to me. RAM 6BQ7A hand tested by Roger. You can play with other 6BQ7A or their "equivalents" at your own risk. Good luck trying to get those output tubes to balance. The driver and output are tied together so the offset of the driver tubes is critical.

The damping of the RM-200 is 10. That puts the output impedance at just under 1 ohm. The nice thing about Roger's amps is they respond well to light loading, which he recommends whenever possible. Meaning if you have an 8 ohm speaker use the 4 ohm tap, a 4 ohm speaker use the 2 ohm tap. Less distortion, more efficient operation, and you get more damping.

There's also an RM9 MK2 listed by TMR with vintage Siemens EL34 tubes for $2,499 (can probably negotiate down to $2,250).  I have the RM9 MK2 and have success with both RAM EL34's and GL KT88's.  Great amp and a great value!   I've owned many tube amps, some that retailed as high as $18K, but the RM9 MK2 is as good as any tube amp I've owned.

That $1500 price for the RM200 caught my eye.   If I were in the market for a tube amp I'd snap it up in a heartbeat!

Me too, @pdreher. I bought my original for $2,000, and sold it for same when I found a Mk.2. Another balanced (via transformers) tube pre-amp that plays well with the amp is the EAR-Yoshino 868L (line only) or 868PL (take a wild guess ;-), or if you’re really flush the 912. I think ARC pre’s should be avoided, as they don’t like the amp’s low input impedance. The EAR’s will drive a 600 ohm load!

Wonder how a Schiit Freya (balanced outputs) would pair with the RM-200?  It seems to work well with several power amps I’ve tried it with so far.