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Mono amps...

are they all basiclly bridged stereo amps or are some designed with a clean sheet of paper as mono amps? I am asking because I have had monoblocks for more than a decade and like the idea of isolating each channel and having the amps as close to the speakers as possible (in fact I miss stereo consoles...just kidding). Being in the market for Bryston 7B-STs, I asked whether they are, in fact, bridged 4B-STs and was assured they are not. Looking at a review of them, however, I read that they are, indeed, bridged 4Bs. Why I should be concerned about this is not clear even in my own mind. I know there are pros and cons to bridging. The slew rate is dsoubled, if I remember correctly. What it all means is a little more blurred. Any thoughts?
pbb
danielk141
488 posts
 
I agree with Sean, talk to Bryston & get your info straight
from the amp builder. I believe the appreciable change in
performance from a bridgeable amp running stereo vs. bridged mode is that the "damping factor" is halved when you bridge a stereo amp. Damping factor can be thought of as a measurement of bass control-how well the amp can control the woofer.
Also, bridging the amp halves the impedence presented by the speaker. If you have a 4 ohm speaker like a Magnepan, the bridged amp will see the load as 2 ohms-a lot of amps can't drive a load that low.

Good luck!
asterix
33 posts
 
just few words
bridged amp(from stereo) = more power - overall sound quality.
tom_munro
162 posts
 
I used to own the 7B STs. There are two modes that these amps can be run in, series (voltage), or parallel(current). I believe the series mode is for impedances > 4 ohms, and may in fact be a bridged 4B when run this way. Parallel mode is for lower impedances, < 4 ohms, or where high current is required. The output ratings for parallel mode are less, but still very powerful. The two modes sound slightly different as well. Series mode has an airier presentation, with a slightly more diffuse soundstage then parallel. Parallel mode is drier, but has a nicely focused soundstage, and controls the speakers more firmly. The 14B looks like it uses one large transformer per channel vs. the two per 7B monoblock.
drrdiamond
671 posts
 
Regarding "Asterix" generalized comment about reduced sound quality from bridging .......
Cello's Performance amps when bridged produced thousands of watts and sounded better than when not bridged.

Richard
nilthepill
842 posts
 
I have experienced what " Asterix" comment in a nutshell. My two Classe CA-400 bridged exactly did just that, confirmed later in so many words by Classe.(more power -experienced by improved control, effortlessness, deeper sound stage. Overall sound quality degreded due to higher noise floor, thinner,midrange suck-out, ambient sound-result: worst compared to stereo mode)
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