A Crown MT series, I think 1200 came across my bench. It has a patented "gr ounded bridge output circuit.
I have been thinking about the ramifications of this design.
The disadvantages :
Of course you need a separate power transformer for each channel because ha lf of the audio voltage is imposed on the secondary of the power transforme r. Thios must cause some problems with capacitance. this has to induce some sort of phase shift, but of course for only half of the signal voltage. An d then, if the transformers have a little more capacitance, you are impress ing the audio on the AC line. Even if you put all kinds of filters in the A C line, you either do it twice or the separation between the channels is de graded. Or you use
The advantages :
You do not need output devices to handle the entire voltage. The thing still only uses two main filters but has totally separate power s upplies. Protection circuitry can be devised without a realy because it is so unlikely that enough of the outputs would short out to make it impossibl e to just send all the others into cutoff under a fault condition. I could do that so I am sure the engineers there can do that and have the thing saf e enough to not result in lawsuits or making it an anaethma in the industry . With the secondaries of the transformers floating, it should be safe as a ... well forget that metaphor, nothing is really safe except a grave.
Anyway, thought I would bring it up in case anyone would like to discuss it .
Page ten of this PDF pretty much explains the concept :
They have also patented a few other things like an even more efficient clas s D amp. And the class I amp wwhich apparently is variable frequency. They say it always switches at zero crossing so with all the varibles in audio i nput, it must be.
I can't find their newer class D info. It requires two inductors, one for e ach output and the diodes go to the opposite supply so they have to handle double the voltage.
I dunno, I never explored that company's designs much until I had to work o n some. Some of it fascinates me. But really, how is that MT series grounde d bridge better than an Ampzilla other than it takes less capacitors ? Oh i t is, but by how much ?
You know that pipedream I posted, wanted to call it class T but that was ta ken ? the one that only used one triac for the output and had the 60 kHz AC square wave supply ? (the one the devices are not quite up to snuff for as of yet). I would like to work with them and see if we can get it down to t hat. Of course they'll never hire me. but it would be cool to see what thei r engineers think about this.
I fully understand what was said in that thread. There are alot of problems with that, but, Crown might not be so scared of it. that is my impression now tha tI seen this grounded whatever thing. What a trip.
And the power for the preamp part comes off the fan motor. A secondary wind ing like you used to see in kid's record players in the 1960s !
This is a trip.