MC275 MK-VI vs vintage MC275 ?
- Thread starter ofery
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Well the input impedance of the MC275 VI is 47,000 ohms but C11 should be used with amplifiers having input impedance of 50,000 ohms or greater according to the Owner's Manual. The input impedance of the MC240 is 250,000 ohm so no problem there.
I honestly can't say whether a mismatch that slight is contributing to the issue.
I wouldn't start throwing money at tubes before diagnosing the problem.
UncleBingo
Super Member
What tubes are in the 275 now and how much listening time do you have on them?
The newer model has better specs so it should outperform the older - at least in theory. But this can fast become a gray area.
The only thing that can be said with certainty is that the older version is definitely better suited for use with the C11 than the VI.
ofery
Active Member
Why is that ?
The input impedance of the original version MC275 250K ohm.. Being that of the VI is 47,000 ohm which is below expressed McIntosh's instructions that the C11 be operated into 50,000 ohm or greater, would strongly suggest the original version MC275 is better suited with that model preamplifier.
As I said earlier, I cannot say how much this is contributing to the issue.
In any case, I doubt tubes are going to be the answer, this side of a faulty tube(s).
ofery
Active Member
My other option is to sell the VI & to buy original 275 instead.
Pio1980
AK Member
For the op, with what preamp?
C11.
ofery
Active Member
So, a "better suited" means a "better sound" ?
Original 275 instead of VI with C11 means a "better sound" ?
In theory of course.
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damacman
Resident Psycho
It may just be that the MC240 is a tad colored in comparison to the MC275VI ... in most cases, it’s nearly impossible to tell this as Mc gear has always been designed to sound neutral. But 5 decades separate the two ...
Or it may be that the output of the MC240 is influenced more by the speakers than is the new amp due to advances in the output transformer design.
Or it may be that the output of the MC240 is influenced more by the speakers than is the new amp due to advances in the output transformer design.
If you go to the Akdatabase and look up the schematics for the C11 ( and for that matter the C22) you will see a rather complicated output filter section.
I see a inductor, a capacitor or two as well as the complicated resistances of series and paralleled resistors within and outside the Erie or Sprague RC module.
I suspect as the load impedence of the ampilfer decreases due to more modern design goals the rather high and complex output impedence of the preamp starts creating new corner frequencies and time constants for the regular output filter as well as the switchable high filter.
Toss in the complexities of some modern litz style multi strand interconnects with their typical high capacitance and I would expect some strange frequency aberrations to start showing up.
Typical interconnects from back in the day were quite predictable what with their simple coax construction with either braid or foil with braid shield construction.
What interconnects are you using?
I see a inductor, a capacitor or two as well as the complicated resistances of series and paralleled resistors within and outside the Erie or Sprague RC module.
I suspect as the load impedence of the ampilfer decreases due to more modern design goals the rather high and complex output impedence of the preamp starts creating new corner frequencies and time constants for the regular output filter as well as the switchable high filter.
Toss in the complexities of some modern litz style multi strand interconnects with their typical high capacitance and I would expect some strange frequency aberrations to start showing up.
Typical interconnects from back in the day were quite predictable what with their simple coax construction with either braid or foil with braid shield construction.
What interconnects are you using?
twiiii
Lunatic Member
The new amp requires extra current the C-11 will be compromised to supply, and is probably what you are hearing. Go back to the older amps with high input impedances. But you have to keep the hook up cables between the amp and pre-amp as short as possible, to prevent cable capacitance from compromising the signal even more.