Reopening an unfinished debate: Dual bridge vs. Single Bridge

[BWRX]

Originally posted by xiphmont
Oh! related question: the note 'problem here: minimize loop area!' implies that, eg, the voltage rails would also benefit from being braided? Ground return included or no?

For a supply with dual secondaries and dual bridges twist the the V+ and Ground wires together and twist the Ground and V- wires together. The loop area on the PCB also needs to be minimized, which means you want to place the local electrolytic caps as close to the chip's power pins as possible, and have the speaker ground and the two secondary grounds as close as possible.

My LM3875 amps use a supply with dual secondaries and dual rectifiers with large electrolytic caps close to the rectifiers. The power and return lines for each rail are twisted together (to minimize loop area) and routed to the amplifier modules where the bridge grounds and speaker ground are connected through a ground plane on one side of that part of the PCB. On the PCB I use one 470-820uF per rail as close to the chip as possible to keep the loop area between the local tank caps and the supply pins as small as possible. The signal ground uses the ground plane on the other side of the PCB and the ground reference is at the plated through hole of the speaker ground.

[xiphmont]

Originally posted by BWRX


For a supply with dual secondaries and dual bridges twist the the V+ and Ground wires together and twist the Ground and V- wires together.

...and for CT/single-bridge supplies, with V+/single ground/V-?

[BWRX]

I would braid the V+/GND/V- wires together, but the large capacitor charging currents will mainly be flowing through the V+ and V- wires for a center tapped secondary with a single bridge (with an ideal center tapped secondary, ideal caps, and equivalent resistive loads across each capacitor no current would flow through the center tapped ground wire).

[xiphmont]

Originally posted by BWRX
(with an ideal center tapped secondary, ideal caps, and equivalent resistive loads across each capacitor no current would flow through the center tapped ground wire).

...except for the speaker load currents. :-)

[BWRX]

There is no speaker load current if there is no speaker

[xiphmont]

Originally posted by BWRX
There is no speaker load current if there is no speaker

While true, this scenario is also not useful :-)

OK, so to the last remaining question: does the dual bridge actually have a practical benefit for a true monoblock, ie, one transformer, one supply board, one amp, one channel in one enclosure?