Try switching your tubes around to see if the right channel has the same issues.
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Thanks everyone for the replies, will change the tubes around and see if I can isolate the problem. For the fuses, I'd think they would work or not work (blown). Is there something to look for in particular? This is my first tube source, but in general how do you know that the tubes need to be replaced? Thanks!
Someone else may want to check this to make sure. When I read a schematic like this (lot of parts) from a pdf reader, I get eye fatigue.
Anyway the way I can see is the V4 and V5 are for the phono. They share the left and right half in each individual tube.
The V6 and V7 (gain tubes) also share a left and right in each individual tube.
So assuming the V4 and V5 was physically swapped left to right side (of amp), the V4 and V5 would have should have replaced the gain tubes V6 and V7. I'm thinking the phono (V4+V5) and gain (V6+V7) shouldn't have a bad section on the same side (half) of two tubes. At least it doesn't seem likely, but strange things can happen. A lot of other parts in there. Possibly a solid state part, or other. You could call MAC to make sure also.
The center tubes (V5 to V7) aren't mirrored on top of the chassis, meaning the two on the left isn't for the one channel, and the two on the right side are not for the right channel only.
All of the other tubes (not center four) are for the side they are on I believe.
Link for schematic for anyone else. [http://www.berners.ch/McIntosh/Downloads/MA2275_ser.pdf]
It would seem odd for two tubes to have a bad side. Those two phono tubes are like a spare pair of used tubes, when using them in the other inputs like CD. It still might be worth trying a couple of new 12AX7s. All the other tubes should change the distortion over to the other channel when you switched them, one would think. Did you swap the CD left and right outputs to the amp to make sure the CD player left channel doesn't have the distortion? Or, use another source, like a spare CD player, DVD player, etc. If you did and no changes, I'm thinking repair time. Don't hold me to this though. Anything is possible...
There are fuses on the power tube board sections of both left and right channels if one of these fuses blows you may get noise like you describe and also low volume output from the channel with the blown fuse. It then may be that a new fuse will correct the problem or there may be a bad resistor or other part on the circuit board. Don't know if this is the problem with your amp but is another possibility.
JLind...Done everything and every combination including moving the Mac to my other system...doing the same thing, its the left channel of the Mac so heading to the Doctor in the morning for 3 weeks of therapy. What really irritates me is I just bought it from someone on AudiogoN as a 9/10 in perfect mint condition. It was doing this the moment I hooked it up and he is pleading the fifth.
G5flier, I would recommend using the augiogon system including feedback and dispute process to get it right with you and the seller. Based on what you have said, the repair should be the responsibility of the seller or you should be able to return it for a full refund. I can see a tube getting damaged during shipping but it doesn't seem like this is your issue.