Will the 4 ohm double if I bridge my Mcintosh???

Hi (Aball) All,

I recently aquired a nice Mc7100 via "The Gon". That I really adore. Thing is it didn't come with a manual. I know from internet searches that it's rated: 100watts X 2 8ohms/ 150watts X 2 4ohms & 300 watts mono at 8ohms(no 4ohm listing when bridged to be found). I also know that I could probably purchase a manual from www.audioclassics.com
But, thought I should try here first.

Will the 4ohm also double if bridged???

Reason for asking is I plan on getting new speakers in the near future and may grab another 7100 (dual mono's) should I decied to go with some power hungry monsters like Dynaudio's, Martin Logan's, and Maggies just to name a few.

Thanks for your time,
Jalen- The ability of an amplifier (solidstate) to double power output when the load is halved, usually indicates a very healthy power supply. The Mc7100 can't do this in stereo mode, and certainly can't do this in bridged mode. This doesn't mean that it may not sound good on the right speakers, but it isn't intended to drive difficult loads (<4 ohms) and still perform at its best when pushed. Of course, there are certainly amplifiers that can double their output power into halved loads that don't sound particularly good, so don't let just this one characteristic determine your appreciation of the amp. Let your ears be the final judge as to the amplifier\speaker combination. Good luck.

Virtually no amplifier actually doubles power into 4 ohms.
Many amplifiers may claim this, but, typically, they are under-rated into 8 ohms, and slightly over-rated into 4 ohms. Unless they have no current limiting, in which case the reliability may come into question. On to your answer...

The mc7100, if bridged , is not designed to operate into 4 ohms. It might overheat and you would be stressing it if operated for extended time at full power. If you do NOT listen very loud, though, and just want a lot of power for peaks, then it will be fine.

Do not stack anything on it, give it a few inches to breath.
The reason that most amps aren't rated at 4 Ohms when bridged is that bridging effectively drops the load in half. In other words, the "300 watts bridged into 8 Ohms" is twice the "150 watts into 4 Ohms" rating, because both channels are driving half of one 8 Ohm speaker. Putting a 4 Ohm load across a bridged amp makes each channel think it is actually driving 2 Ohms. The amp isn't rated for it, and will likely get very hot if you drive it at high levels (which is usually the justification for bridging in the first place).
Thanks for the input guys. Looks like my new speakers will be limited to Newer Klipshes & Or Paradigms then. Or Maybe a "Big O' Mac" will be in my future as well, LOL. I'll hate having to get rid of the 7100 it's really a nice sounding\looking amp.

Yeah, The Book on My Rotel RB 976 states that when bridged do not connect anything less than a 8Ohm load as well.

Kzelin: your right about these amp ratings. I've only seen a couple that claim to have ratings down to 2ohms and they were from Mega-buck Comapanies like Krell, Sunfire, and I think Mark Livengston (sp?). It's hard to beleive how people are getting power to such speakers like ML's which are known to get as low as 1ohm for the highs.

I guess I'll hang onto the MC7100 to try on whatever speakers I chose, as JCBtubes suggested. But, I'll always keep notes of what the dealers were powering My final speaker candidates with.
Hello Jalen, just try Tannoy's Definition line on your (s) 7100 and it will sound wonderful. The Mac-Tannoy couple is one of the best. If you go for a bigger Amp like 2255, 7270,7300 or 352, just test the D700 and D900, they're amazing loudspeakers. Good luck. Yannick.France.
if you are still looking for the manual,go to www.berners.ch/McIntosh
In the section Amplifiers 2 you'll find the manual to download for free