Dynacord "3-stage grounded bridge" amp

[wg_ski]

Originally posted by rtarbell

==> What supply voltages are needed in the first and second stages? For instance, if a grounded bridge amp has a maximum voltage supply of 75V on its output devices (floating, so the load could either be +75V or -75V maximum), then does this mean that the input stage and VAS stage should be powered from a conventional +/- 75V supply to prevent clipping?

The VAS on the high side runs off the floating supply. The low side doesn't need a VAS, the output of an op amp on +/-15 (referenced to the ground it's driving) is all that's needed - just like a QSC amp.

==> Sandman proposed a bridge amp scheme circa 1971 that has a small high quality amp (A2) controlling a larger quick-and-dirty one (A1).

Yes, I *think* that this was the beginning of the SMALA amp (switch-mode amplifier linearly assisted), where the class-D amplifier (high efficiency, not so great distortion) supplies the majority of the current, and the "linear assistance" class A (or AB) amplifier provides the small correction current to smooth out the distortion. These currents add before reaching the load, and theoretically, the result is a high efficiency, better linearity amp. Correct me if I am wrong in my assertion here.

The low side can have fairly high distortion because it drives the "ground" which is the same as the input ground. Distortion products become a common-mode signal, and in effect, show up on the floating supply. If the high side amp has good PSRR, it rejects it. Some of Crown's amps have a "dirtier" low side amp (especially the bias circuit which won't track as well over temp as what they use on the high side).

[Workhorse]

Originally posted by wg_ski


The low side can have fairly high distortion because it drives the "ground" which is the same as the input ground. Distortion products become a common-mode signal, and in effect, show up on the floating supply. If the high side amp has good PSRR, it rejects it. Some of Crown's amps have a "dirtier" low side amp (especially the bias circuit which won't track as well over temp as what they use on the high side).

Seperate amp for each half bridge in a GB Amp is followed by Crown, which is not good in terms of sonics
but if you go for compound GB amp using true differential IN-differential OUT, then the result is awesome, i have designed it using Diamond Differential input and Balanced Grounded Bridge output along with 2 Step Class-H........