Music Reference RM-200

The original can be sent in and brought up to Mk.2 status in every way except for the capacitor forming capability.

No it can't. I was never aware of the upgrade, Roger never speaks of it these days, and if they were done in the past they aren't going to be done any longer. We will continue to service RM-200s.

The 6BQ7A supplied by the Tube Audio Store are the correct driver tubes as they need to be aligned for offset which Roger does (and I will soon be doing) by hand. As for the output tubes, RAM KT-88 are stock, most folks like the Gold Lion KT-88, and my personal favorite is the GE 6550. Some people run KT-120, good luck with that.

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.

We don't brand the Gold Lion KT-88s so those could have possibly come from us. We brand the Chinese KT-88s. I'm pretty sure our 6BQ7s are Sylvania but we brand them as well.

One way to determine how well balanced the output tubes are is to take a volt meter, set it to volts DC, and preferably set to measure for mV. In the back of the amp at the binding posts, for the left channel put the red probe in one pot and the black probe in the other and you can measure the difference, which should be quite a small number. less than a couple of mV. Then repeat for the right channel. You should also check the bias as well after the amp has been on a while. A good reading would be around 36 mV.

The RM-10 is my favorite MR amp. I've owned one for over 10 years now. Great match with my Lightspeed Attenuator. You really need an active or buffered output preamp with the RM-200 as the input impedance in both unbalanced and balanced is fairly low. I've spent a lot of time with the RM-200 as well. It's a nice amp and if you have speakers with difficult loads it's an amp that can get the job done as it increases power as the speakers impedance drops.