The right amp to biamp with McIntosh MC275 Mk V?

I don't know all the history, but the Mk IV vs. Mk V:
IV has a splitter tube, and gain controls. V doesn't.
IV has speaker terminals that only allow spades. V allows for bananas.

Hello, I see all these references to McIntosh MC275 different versions. I wish someone could run thru (for me) any chronology and what the differences are (how to tell one version from another). The versions I am aware of are:
1-I'll lump all amps made during the 60's and 70's as ORIGINAL.
2-The first reissue that I know of (a "Gordon Gow" edition)
3-An edition where it has the plastic barrier strip, gold balanced inputs, RCA's below, and black gain knobs, etc.
4-A version where speaker oututputs are newer binding posts for bi-wire, gain knobs are removed, etc.

There are probably a few versions I may be describing here, so any info on full list of versions and or links to that info would be appreciated!

A further look into the Spectron manual revealed that if you run this amp unbalanced the gain will dip to 26 db-a perfect match for the Mcintosh in unbalanced mode.They are both in Harmony now and the listening test lies ahead.A few hours today reveal a really good match.Now i can listen to both together,a tube amp by itself,or the mighty Spectron exacting judge,jury and executioner to all that lies in it's path.
Sometimes you have ask a question to get the answer you had all along.Great listening to all!

Thank you for your comments.Thanks to Velo62 i got the information from Chuck at McIntosh.Here are the Gain specs for the MC 275 MK V....Balanced- 4 Ohms=16.8 db 8 Ohms= 19.8 db 16 Ohms= 22.8 db
Unbalanced- 4 Ohms=23.2 db 8 Ohms= 26.2 db 16 Ohms= 29.2 db
My initial biamping adventure is with the Spectron Musician MK 111 and the match is tolerable sonically on compact disc performance (EAR Acute) but the Vinyl reproduction is far too bass heavy.No surprise there as the Spectron is rated at 26 db gain and i am running balanced at 19.8 db. If i go to unbalanced i will be a closer match.I will try that today and see what that sounds like.
Several other issues come up....A great amp like the Spectron relegated to simply the lower portion of the signal.Is this rather like having a sports car that you never open up past third gear?
I did try a Channel Islands passive controller but i found,though it reduced the volume of the amp,it also reduced the voluptuous sonic bouquet.
Just from hearing these two amps on these speakers has inspired me to find a decent match and pursue this as everything is improved with the McIntosh concentrating on the Mid and tweeter.As one commented to really HEAR an orchestra you have to biamp.I found this so true as the sections stand out in almost 3D like effect.Someone else said that if you want to hear great acoustic Jazz you must have tubes,tubes and more tubes.This i found true as well.
Same goes for string quartets and pianos.
SO.....solid state amp with 19 db so i can run the MCIntosh in the balanced mode?
I really do not want to resort to a crossover.I would consider a second McIntosh.Thanks Again!

The best way to biamp, I've learned is to go for active design i.e. using electronic crossover and removing/bypassing the built-in crossover.
Otherwise you will jeopardise the dynamic headroom of your system.
Another way has already been mentioned to use another same amp.

Wouldn't a Mcintosh MC452 be a great choice? You could connect the MC275 input to the balanced output of the 452 and attenuate both amps from the input of the MC452 to the preamp with identical gain. Maybe a call to Mcintosh and some advice from Chuck or Ron could confirm this would be a good idea.

agree....

Jazz keep me posted on your decision.

I think this will be really tough to match proper gain. My recommendation is another MC275 run in mono.