McIntosh MC275 V jumper cables/ wires for parallel use

oldhvymec:  “Yuk” was not my experience at all when running a pair of MC275 Gordon Gow Commemorative edition amps as monos (paralleling the 4 ohm taps) into my Martin-Logan Quest electrostatic loudspeakers for over 20 years.  The Quests dipped to near 1 ohm in the top octave but rose markedly in impedance as it neared the crossover point to the big 12” woofer at 100Hz.  ‘Stats DO tend to be quite revealing.. I never took the temperature of the amps but I did measure current draw, which was the same whether operated in stereo or as a monoblock, about 3.6 amperes.  I replaced the initial set of output tubes (USA made Richardson KT88’s) after 12 years out of caution and amazingly they still met specification.  The second set was Svetlana KT88’s from the St. Petersburg factory and they comfortably exceeded spec when I sold the amps several years ago when I downsized after a move. The MC275 is amazingly easy on output tubes but at the expense of the driver tubes, in recent 275’s 12AT7’s, on mine the near-equivalent 12AZ7 which are still commonly available NOS for under $10 since they’re primarily were used in TVs and were branded Zenith, Motorola, Channel Master, etc though they were all manufactured by either GE or RCA.  As far as the OP question, I made my own jumpers from several insulated 6 nines copper wire strands retrieved from a scrap of Audioquest speaker cable and some nice AQ spades.

The Older Macs can be in series or paralleled. Look at the schematic for a 240 or 275. A pair of MC30 or 60 same thing.. You can stack the old  Macs..

Bridged is in series. Usually 8 ohms is the lowest you want to go.

Paralleled a Mac will do 2 ohms. RUNS HOT but it will push 2 ohms in parallel. SQ wise, YUK!! you need to be at least 6-8 ohms to help it out.

Mac has a sound, stacked or in parallel they do sound different.. Parallel is better in MOST cases.. Distortion goes up .5 to 1-2%. You'll hear 2% if your speakers are revealing at ALL. Usually high E speakers.. 90+

The weird thing is you might like the 2% distortion.. Just a tube thing..
I like it just a tad cleaner. .5 is plenty at 1-10khz

Regards

Got it, looks like a bridge circuit. I'm not a hybrid amp expert, so I'm going to stay out of it. Guessing that when you are using output transformers, that may be called parallel. Good luck!

From what I understand of setting these amps as single-channel amp, McIntosh calls this "Parallel" versus that of "Bridged".  I read somewhere there's a difference between the two, but I cannot recall what that difference is.  So yes, I would like to run these MC275s as monos (one MC275 for the right-channel, & another MC275 for the left-channel).  When running these in parallel, the amp does still "see" the speakers OHMS at half.  So the 16ohm tap on the amp is needed for a set of 8ohms speakers. 

Thank you for asking on this. 

Help me understand your term parallel. Are you talking about bridging each MC275 amplifier for mono use?