Is the moscode 600 a great amplifier?

Replace the tubes with either Siemens E188CC/7308 or CCa, and the sound will be transformed greatly. Then there's the upgrade path as well: (http://moscode.home.att.net/M_mods_upgrades.html) People don't ususally bother with modding products that aren't worth it in the first place. If you are stuck on SS amps- Don't let the slight "mist" of the MOS-FET bother you. That's a great improvement over the grain, glare and edge that bi-polar transistors exhibit. Yes- The Hafler TransNova 9505 is a great SS amp also(I power my woofers with one). FET front-end instead of the tubes, pure class A, fully differential, and MOS-FET outs(also slightly "misty". That "mist" takes a trained pair of ears to notice, BTW.

Perception seems to be one of the most determining factors for what people hear. But most designs can sound good, even MOSFETs.

The amps are even better now. Remember these are a pair of the Max mods that George Kaye does. I have Russian NOS ('79' & '81') 6H30p-DR in the four input positions. I have four Amperex Bugle Boy 6DJ8s (early '60's' in the four driver positions. And a Pope NOS 7 yes 7DJ8 in the regulator positions.

The amps are heavenly.

It is powerful, reliable, and more tube like then transistor.
It drives just about any reasonable load, and even some unreasonable ones.
IMHO, it is THE amp to have if you are a guy like me, always changing, or owning many pairs of speakers.
The Moscode 600 is a LOT better amp then a Moscode 300.
The Moscode 600 can be tube rolled to sound like you want it to.
This means you will not have to buy a new amp to get your new speakers sounding right.
Simply roll the input tubes of the Moscode 600, and change the sound as you wish.
They go for around 600 to 800 dollars.'
At that price, it is a no brainer.

One further thought on modified and tube rolled Moscode 600's.

George once told me that he had bridged some 600's for a famous record maker (to remain un-named), because that is what they wanted. However, in his opinion they did not sound as good bridged as they did vertically bi-amped.

Never the less, based on experience with a different pair of amps in the late 70's. I kept trying to bridge them.

First I used a transformer input. Interesting result, but George was right. Later I bought a SS bridging unit with absolute polarity switching, still not as good as vertical bi-amping.

Eventually I bought a preamp with balanced out, but no absolute polarity switch. I built a little box to convert the balanced out to single ended with switches for absolute polarity. The box also gave me the ability to bridge the amps.

WOW, WOW, WOW!! That was what I was looking for.

I now have two preamps with balanced out, one SS, one tube. They both do a fabulous job of bridging the amps into 1000+ watt monoblocks into an 8 ohm load.

The good news is that the amps were originally stable into very difficult loads. Because they are bridged into a pair of Martin Logan Prodigy they need to be stable. These speakers are nominally 4 ohms with a dip to 1 ohm above 15kHz. Running the amps bridged the amps effectively see 1/2 that load, so a dip to 1/2 ohm.

If you are willing to do a little, to a lot, of work with them the 600's can really shine.