Mixed driver tube for Mcintosh MC275

Okay, after viewing the schematic, it is clear that V1 is not in the signal path. Then what am I hearing? Voodoo? I am obviously crazy! Now I am convinced as to not buy anymore tweeks because my hearing is somewhat flawed.

I thought I noticed a more full sound with the other tubes I used. This is crazy. I am going to put my one pair of balanced cables back into the amp and see what I hear. I did ask the tech and he did say it was in the signal path and would have an effect on the sound. I felt I was pretty clear on how I asked the question. My mind is obviously playing games with me. This is a very informative thread. Maybe I will try different balanced cables and see what happens. There I go again, tweeking.

Tzh21y --

1.) I don't think there is anything at all wrong with your hearing! I'm 68 and I KNOW my hearing isn't what it used to be (to say the LEAST!!) however my ability to LISTEN is better than ever ;--) I wish I could go over your system with you in person, because I know I could find out what is keeping balanced operation from sounding completely marvelous and far superior to single-ended.

2.) My long experience talking with McIntosh technical people (even those at the top) has been 'highly unsatisfactory' to be diplomatic about it ;--) You would have better luck talking with one of the engineers; at least they understand English, but they are harder to reach. See if you can get hold of Ron Evans, V.P. Engineering.

I have a couple of system specific comments:

1.) JPS interconnects are OK (as in: decent)
2.) Everything "Cardas" sucks! Way too much capacitance (especially for your Merlins) and terrible time-alignment. There may be a couple pieces of equipment on the planet that one could connect with Cardas cables, but nothing I'd want to own! ;--))
3.) I'd be interested in knowing what kinds of (good) tubes you own for the amp, and -- I almost forgot -- what (if any) tube changes you've made to the C220?

Neil
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I have the Cardas on the CD player. I am listening ( auditioning) to JPS superconductor 3 cables connected to the turntable. I can see how some can be critical of them. I have NOS Telefunkens in the C220, all Telefunkens in the 12ax7 position in the amp, GE 12at7's and Tung Sol 6550 in the 275.

I am going to plug the XLR's back in try that V1 thing again. If it still sounds different,

Tzh21y -- If you like the JPS product, you should stick with them, perhaps throughout your system for synergy. I just don't like (almost) any of Cardas' products because of their high capacitance (especially of their speaker cables) and the excessive time smear of their interconnects -- all due to all that "Golden Section" multistranding ;--)

Did your MC275 come with 6550 tubes? And what vintage Tung Sols are they? I ask because you might want to try a quad of KT88's which are more powerful and some say more accurate. I haven't tried 6550's in my amp, so I haven't compared the two. The best price/performance current KT88's are the SED's (yes, I've listened to them and tested them ;--) You can get a matched quad here for about $170 http://www.conusaudio.com The other tubes you are using are OK for now pretty much, except if you are using the C220 phono section, I would recommend tubing that part with 5751's -- either Sylvania or RCA triple-mica blackplates for ultra-quiet, great dynamics, and smooth top-to-bottom frequency response.

In order of bang for buck:
1. KT88 power tubes $170
2. JPS speaker cables (??)
3. Sylvania blackplate 6201's (12AT7's) $150/quad
4. JPS for the other cables (??)
5. RCA or Sylvania TMBP 5751's (12AX7's) for the phono section. $140 or $200 per pair respectively.
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I have 2 RCA tall plate 12ax7s that I am not using. Maybe I should try them in the phono section. I do not find the Cardas to be as bad as you are saying. They are decent cables. I may try the Anti Cable interconnect. I cant go wrong for $100.00. If I do noy like them, I will sell them here. Many here are tossing their expensive cables in favor of them. They have spent much more than I on their systems.