Haven't looked into schematics of the Lab Gruppen, but wouldn't the voltage levels become a problem for the zener diodes?I would go for class H (continuously variable power rails), look up the well respected Lab Gruppen pro-audio amps for idea's (schematics freely available).
Load impedance is simply a matter of design as I am sure you are aware.
@ Fourtytwo, class H uses switching supplies - which per the post are too noisy - please re-read the post more carefully before typing
I saw and heard electostatic speakers about 50 years ago driven from a special vacuum tubes amplifier. They produded a lot more than only 400Hz.@ Auidogubu there are in fact electrostatic speaker drivers that go up to several kV, i.e. low current and high volts - some what in contrast to your post above ....
Class G uses multiple power supply rails ( fixed ) and effectively series transistors which are turned on as the output level is driven higher - the picture above describes it exactly for a 2 voltage system ...
I once worked with a design extremely similar to the one in this picture (in fact it wouldn't surprise me if the engineer who did that design based it on that very schematic). One of the very annoying things about it is that dissipation vs output amplitude is maximum somewhere in the mid range. There were times when setting the amplitude to 30% or 70% was fine, but in between it would melt because we were operating too much near that worst case operating point. We were frequently trying to tailor it to the waveforms we wanted to produce.Apologies to all - but just really seeking input as to Class G design - the load will be largely resistive with 0.8 PF lagging - I am now leaning towards 3 rails, +/-100V +/-200V & +/- 310VDC as the lowest loss design for an output ( now increased ) of 600Vpp at 2 amps rms.
As stated above the main test freq is 400Hz - but the amp will be DC coupled, allowing 0 - 400Hz
We do not need clean 0v x-over, and can tolerate small glitches as the rails are crossed - as it is mainly a power/endurance test
The rails will be supplied from ultra quiet switchers, and we may use BJT's for the 100V & 200V level, and 400V fets for the 310V level - with substantial zener protection across each.
The whole circuit and drive is pretty simple for 2 level - per the image attached - was hoping for tips and tricks from someone who may have designed similar as we build a 3 (6) level version ...
kind regards,
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