Mc 240 vs. Prima Luna

@russ69

"Although mono-blocks are better than stereo amps, bridging a stereo amp is not the same thing as a pure mono-block amp." 

I agree, the key point is bridged amplifiers are not the equivalent of a true  mono block pair. 

In addition as the late almarg  would politely explain,  bridged amplifiers will see 'half' of the speaker's impedance.  8 ohm becomes 4 ohm, 4 ohm load becomes effectively 2 ohms. As a result,   the bridged amplifiers are asked to drive a more difficult impedance load.  Better to obtain genuine mono block amplifiers. 

Charles 

Yea, just not with 240s in parallel or in series, you can run the 240 and 275 EITHER way. A MC275 were made for Klipsch Honestly a MC240 stacked is for PA, it will run the speakers just fine, they just won’t be the sweet sound of a MC240. They are VERY special one way but not EVERY way. They like 8-24 ohms too. They just sound better.

50 years with Mac, I’d be changing back to a MC275 before the bill started to fade if I was looking for true Mac sound.. Or better yet try a Cary V12r.. LOL Second best amp I’ve ever owned.. What a wonderful amp AFTER I worked it over.. I love it..

I’ve had VTL 750s and 1250 Wotons here a few times.. I’ve listen to a LOT of amps and did a lot of work on others..

A real nuget is a MC225 with just a PS upgrade and a few PIO caps changed for some of the non MPWs but NO yellow pollies.. They use MPW metalized polypropylene, DON’T you dare change them. They are the wonderful sound of the little MC225 amp.. Just make sure on the resistors and check for tolerance in the caps.. Virshay coppers are a GREAT resistor.. Pure (?) too I think it’s Pure..

Regards

I've heard the nasty downside of bridging, with solid-state amps which I loved in stereo mode (Phison A2.120 SE), and they lost their sweetness in mono/bridge. But tube amps can be a different story, probably in part because you can change taps to manage the different impedance. Also they won't just "double down" the current & power while straining the PSU and output stage. My VAC switchable mono/stereo tube amps sounds by far the best in mono. 

But @oldhvymec has experience with the MC's, doesn't like bridging them, and that trumps theory. So that's a solid vote against mono/bridging the MC240...

Kevin Hayes discussing his VAC 200 IQ amplifiers With Hifi news.com, 

"With respect to overall power, it's generally been forgotten that very soon after the inception of the KT88, nearly 70 years ago, the GEC/Genalex data sheets showed a 100W/pair operating point in its application circuits' says Kevin. 'In practice, we find that some pairs of KT88s will exceed 100W. The KT88 delivers exceptional sound under these conditions and, in our circuits, average tube life is quite good – typically 6000-8000 hours.'

VAC's custom output transformers are also core to the amp's 'real world' performance. 'In stereo mode the taps are effectively for 2, 4 and 8ohm; in mono, a parallel operating configuration, they are effectively 1, 2 and 4ohm. So, in mono mode [as tested here] the maximum power, lowest distortion, and widest freq. response occur into a 4ohm load on the top tap, which is labelled "4-8".

'Most audiophiles will try more than one tap to see which best suits their loudspeaker (with its varying impedance curve), so we label the taps with a range rather than a single number'.

So it seems in "Mono" (Bridged) mode the amplifiers are seeing 1/2 of the speaker's impedance they encounter when in stereo mode (As almarg described).

Anyway the bottom line is what the listener hears and likes.

Charles