Try switching your tubes around to see if the right channel has the same issues. |
Yes, it could be a tube but I have also heard a bad resistor sound like this too. |
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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! |
OK changed the tubes from right to left and still having an issue on the left channel. Does anyone know if the MA2275 shares any of the tubes? |
One more check. Trace your cables on the left side including speaker and IC.
Not sure about sharing for the MA2275. |
Lapierre, checked the cables and the interconnects, even removed them and connected with bare wire still having the problem. You said to check the fuse before, wouldn't the fuse either work or not work? Their is only one fuse so wouldn't that effect both channels? It's a slo-blo type fuse. |
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] |
I hope your using other inputs than phono also. And, if it did the same with other inputs, the above would have worked. Otherwise it could be a bad gain, or phono tube if you just used phono in. |
The center tubes (V5 to V7) aren't mirrored on top of the chassis, meaning the two on the left Correction: Should have wrote (V4 to V7)... |
Hifihvn - wow thank you so much for looking over the schematic and comments!!! I'm only using the CD input, not phono at this time. I did swap CD and CD2 but same result. |
I should clarify. Section B of V4 and V5 tubes are for the left channel. Section A of V4 and V5 are for the right channel in these phono tubes.
Section A of V6 and V7, tubes is for the left channel. Section B of V6 and V7, is for the right channel of these gain tubes. |
Hifihvn, again thank you! So given what you have found out what do you think is the next step? Should the tubes be replaced? Something else? Thank you! |
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... |
Are you positive it is the Mac? Have you swapped ICs left to right at the source only? Or try another set of interconnects from source to amp. You may be looking at the wrong component for trouble. Good luck. |
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. |
Kbell...thanks for the input about the fuses on the power tube board, the channel with the distortion problem is actually louder than the channel that works well. |
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. |
G looks like your getting pretty good feedback. Nothing I can really add here.
I did reach out to Mc customer service after my tube blew just to ensure I understand my options.
Good Luck. |
A big thank you to everyone that replied to the thread, many great ideas! The 2275 is heading to the doctor in the morning. |
The MA2275 came back from the Dr today with a clean bill of health...blown resister on the left channel was the problem. Thank you again for all the advise, everyone was really awesome and a big help. |
Glad it was something simple.
Thanks for the update. |
