amp bridging

[steelervic]

can any two channel amp be bridged? if not, why?
thanks, vic

[steveinaz]

You know, I've wondered this myself. I had 2 Soundcraftsmen amps that were "bridgable" but used an external bridging adapter. You plug your preamp into the bridger inputs, then there is connections for each amp into the bridger. It got me thinking "why wouldn't this bridger work on any set of stereo amps?". I'm no electronics guru, but it looks like the bridger ciruit does nothing more than invert phase on one of the channels, allowing you do use both positive connections off of each amp; effectively tripling the output power. In this bridged configuration, the output went from 205 watts/rms to 600 watts/rms; of course this is Soundcraftsmens' specification.

We need an electronics guru on this one...

[RuSsMaN]

Most dual-mono designs cannot be bridged. Even some amps that share a power supply cannot, for example the early Adcom Nelson Pass designed amps - 535, 545 etc.

The only thing I've noticed, and it's probably irrelevant - is that on the stereo amps that CANNOT be bridged (that I've come across) - the chassis ground and signal ground are separate.

No guru here, but I think it has to do with the design of the amps output stage(s) and grounding system.

Love to hear more on this topic.

Cheers,
Russ

[steveinaz]

I was thinking the same with the output/grounding scheme. The Soundcraftsmens' used the Class "H" design (rail voltage) and were "non-current limited." You could literally "short" the speaker terminals, and the amp would simply reset, with no damage. Maybe this plays into it somehow....

[Phil Dawson]

In my experience amps have to be set up properly (ususally in the manufacturing process) to be bridgable. If it were me i would consult an authorized service tech or the manufacturer to see how the amp was origanaly set up.
Phil

[Tour2ma]

sure "bridgability" has to be designed in, but what's the key design element?

first thought here was common ground design, but there is at least one, sunfire, that is not bridgable...

henry? manamp?