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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