Yamaha's new floating and balanced power amplifier

Latest High End HiFi power amplifiers from Yamaha use their floating and balanced circuit. Power transistors are same polarity MOSFETs for both halves of waveform and the circuit is complety floating. Any ideas for DIY version? Do you think that it is promising circuit?

Yamaha says:

The basic design of the power amp circuit adopts Yamaha’s own, uniquely developed Floating and Balanced Power Amplifier technology. Adopting output elements with the same polarity on the plus and minus sides of the output stage, and also completely separating the NFB (Negative Feedback) circuit and power supply into total of four plus and minus sides of the left and right channels, results in thoroughly symmetric push-pull operation of the output stage, Completely floating the entire power amp circuit from the ground removes any negative impact of minute voltage fluctuations or ground noise. Moreover, the output elements are comprised of MOSFETs, which provide a warm and natural sonic character. The use of MOSFETs, which have the same polarity on the plus and minus sides, further evolves the ideal of a complete symmetrical design, to eliminate sound quality variations due to difference in polarity—a major distinguishing characteristic of the Floating and Balanced Power Amplifier—resulting in sound with a superior signal-to-noise ratio and superbly well-defined sound field.


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my little Circlotron, the Zirclon140, sounds very well. I never have such a silent amp, no hum and very less noise.

I have Circlophone with JFET input and it is perhaps my best sounding amp from standpoint of great bass dynamics, overall transparent response without adding coloration - smooth mids and highs with no sibillance. It sounds like a class A amp without the class A heat output.

That is also my impression.
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Hi there,

I get the whole floating ground concept, however what seems to escape from my understanding is the Yamaha's output stage configuration, see the Yamaha A S1000 schematic (you have to download it):

YAMAHA A-S1000 SM Service Manual download, schematics, eeprom, repair info for electronics experts

Can one explain it to me, please! What are we talking about here? Is it a triple common-emitter output stage, as oposed to a triple emitter-follower, and if so, does it make sense from a performance perspective?:confused:
It is a circlotron-push-pull topology with common-emitter output stage, a nice topology if you ask me. Multiple cascaded common-emitter stages tend to produce a distorted, excessively bright soundstage. (Very high THD).

Thank you N101N, for your reply. But, following the dashed line (pink) in the attached picture what is the configuration of the pair made by Q222 and Q223? Also, I was expecting that their collectors would be connected to the positive rail, not to the load, what am I not seeing here? :confused:


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In my interpretation, Q222 and Q223 form a common-collector Darlington pair driving three common-collector 2SC4468 in parallel. The outputs are (should be) at the positive rails (and referenced to input ground).


If you follow the pink dashed line, which is supposed to represent the signal path, you see that Q223 and Q222 (pre-driver and driver, respectively) form a darlington pair, as their outputs are taken from their emitters, and then the they fed the output transistor Q219, which in turn is connected to the load from its collector (common-emitter configuration). Thus, the 3 transistors, pre-driver, driver and output don't form a triple emitter-follower, which would be otherwise expected.

I've never ever seen such an arrangement, what I'm missing here?

Also, I don't understand how the collectors from Q222 and Q223 are connected, because they seem to be connected to the load. HELP!
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Sorry to have kept you waiting. The collectors are directly connected to the positive supply rail (which counts as ground) and to the loudspeaker load. This point has to be elevated above input ground potential. Definitionally, the 2SC4468s are common-emitter amplifiers and the predrivers are common-collector amplifiers - behaving as common-emitter amplifiers. The ouput properties of the common-collector amplifier are relevant for driving the next stage, while the same amplifier looks different from the perspective of the loudspeaker.