using two Mcintosh MC2102 in mono parallel mode

Steve, 0,7ohm looks incredibly low to me. R U certain of that figure? If so, you'll have to mod the amp to take that sort of load (unless this has been provided for already), and, geberally, tube amps are extremely unhappy with very low loads.

I'm not sure what parallel mono mode is; if it's bridging each stereo amp to amplify mono then the load impedance the source will see will be halved UNLESS Mcintosh has a different design provision (which they'll specify).

Amp sensitivity: shouldn't change, but again, I don't know the effects of bridging on yr amp (McIntosh probably specs this in the manual).

Matching the tubes: let's not go overboard:) As long as the tubes on the old unit aren't severly tired, it'll be OK. In any case, you'll hear the differences if any. UNLESS you mean, should the two amps be using the same brand of tubes -- in which case the answer is yes.

The folks at mcIntosh Labs are very helpful. Give them a call. I own the 2102 and I am very happy with it.

what kind of speakers are you running that dip that low & what is their rated nonimal impendance? when you go paralell with the mc2102 the impendance drop's from 16, 8 & 4 ohm's to 4, 2 & 1 ohm's,i would think that your speaker's would reek havok on a mc2102 running it in stereo mode due to the low impendence dip,even if your running them from the 4 ohm tap the dip you mentioned is extremly low & cant be an easy load for that amp,does your current single mc2102 handel such a dip well?

if your speaker's truly dip that low then your probably on the right track getting another amp & running them in paralell because in paralell you can try your speakers on the 2 ohm tap or even the 1 ohm tap without putting such a demand on the amp.

i dont think ive ever heard of a speaker that dip's down to 0.7 ohm's are you really sure that figure is correct?

mike.