To "tube" or not to "tube"

Tennis, congrats! You're going to really love that amp! The power tubes the MC 275 comes with are KT88, either Electo Harmonix (round holes in the plate) or Svetlana Winged "C" from the St. Petersburg plant (square holes in the plate.) The Penta KT88SC copy (SC stands for "strict copy") of the GEC Gold Lion/Gold Monarch KT88 are suposed to be the ones to have. I just ordered a new matched quad from a member for $100 shipped. I'll let you know on those. As for 6550's, you can also run them in this amp, but for my money, they're not as nice sounding a tube as the KT88. (Maybe a teentsy bit more power though.) The amp has neither bias adjust nor auto-bias; it's not necessary for the Unity Gain circuit design. It's good though to have matched pairs of power tubes and gain multiplier tubes in each channel.

For the 9-pins, I will be trying Mullard, GEC, and Amperex/Holland in addition to the Teles (what's up with the RCA's?). All I know is, the McChina's suck, IMO ;--) The tubes that make the most difference in sound are the three 12AX7's. Or just the two 12AX7's in V2 and V5 if your using the balanced inputs.

I'll be anxious to know how it sounds driving 1.6's. However, mine sounded like crap for the first five hours! Tubby, boomy bass and grainy mids, yuk! So do give the amp a 50-70 hour break-in before you evaluate it ;--)

hi neil:

what fo you think will happen if i use lower gain 12ax7, namely 5751 ??

according to mcintosh, changing tubes will not change the sound of the amp very much. a dealer told me that the 6550 gives a more romantic sound than the kt88. in any case, i won't be getting the amp for about 10 days.

I don't believe the 12AX7 does gain multiplying, but you shouldn't take my word as I'm not a tube circuit maven ;--) Check with McIntosh technical support.

I know what everyone connected w/ McInt. says about tubes not making a difference. All I can figure is they're all listening to McIntosh speakers ;--)

As for 6550's, I had 8 Svet. Winged "C" (per side!) in my ARC monoblocks, and I wouldn't characterize them as "warm and romantic". More neutral and dry. Now maybe that was just the ARC amp, I don't know, but many audiophiles and lots of electric guitar players seem to favor the KT88's, which let's face it have only started to be re-issued in quantity relatively recently.
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Nsgarch, You (and the rest of you guys) have been a big help, given me lots to think about, I like the idea of 275Mcs mono blocs for either speaker set ups, so will be on the lookout. the next question of course, is pre-amps... And to Beheme, couldn't have said it better myself.
jb