BASH and expired patents


FYI, everyone, the BASH patent is basically expired and that is where ’new’ amplification will very very likely...begin to shift into. Don’t know the exact dates but this is what it looks like is happening..

Just a prediction in potentials, is all...

Basically.....BASH is a class AB or C-ish output stage, combined with a pulsed power supply, where the rail voltages dynamically shift in level, in conjunction with the signal.

This is what class D was trying to side step, one might say -- the BASH patent. The BASH/Indigo patent was considered (by me) the better way but it blocked the path forward.

Now that path is again open and it will very probably be the new thing.

The whole idea is to gain efficiency, but have a non switching output. The BASH patent was the best compromise of quality and efficiency.

For the purposes of high end audio, the ending of the BASH patent will probably spell the end of high quality audio oriented class D amplifier development.

That was a 20 year delay....

The trick about Class D, is to remember or cognate the why of it in the first place. The pulse modulated output is not ideal, the filters can only do so much and create huge complications (The pulsed output and filter as a combination).

BASH sidesteps the worst intractable problems of Class D amplifier design and execution... and gives us the best that a high efficiency compact system can do. The problem of development in that area, was that the BASH patent blocked that entire spectrum of design pathways.

Now that path is open.

I speak a little on it (preliminary realization and musing) over here.
teo_audio
Honest, I cannot agree with much of what you have said.
I don’t see digital as at all a step backward, and see 24/192 or high bit rate DSD as vastly superior to any analog format, tape or vinyl, but really we only need to compare to tape, as any vinyl is either an analog conversion from tape, or more far more likely for the last few decades a digital recording finally transferred to vinyl.

I can see one liking the euphonics of vinyl, which is what most people consider analog, especially the reduced channel separation and increased cross-talk, which in the absence of a well tuned room, may provide a level of ambience that is lacking from a digital stream (but which could be simulated). Even that low level background hiss can add a sense of realism. But for pure accuracy of recording, vinyl or analog tape just does not have the "chops" to compete. It simply is not even close.

For me, I do see the filter as somewhat trivial as when my PWM rate is pushed high and my pulses reasonably symmetrical, quite possible today, then anything that is not music is pushed way outside the audio band and can be filtered in the analog domain such that anything near the audio band is well below anything a human could detect, and the same would be true with near ultrasonics so you don’t have any weird speaker breakup modes. Class-D also has some inherent advantages with a good power supply design for reducing IM and multi-spectral modulation in real music.

Long term, digital signal processing will allow corrections to what comes out of a speaker that simply is not possible in purely the analog domain. That pretty much makes it a necessity towards what may be consider our holy grail.
Basically.....BASH is a class AB or C-ish output stage, combined with a pulsed power supply, where the rail voltages dynamically shift in level, in conjunction with the signal.
Class H appears to be exactly that - class AB output with modulated power supply to minimize power losses.  This scheme is used in my Benchmark AHB2 where modulating of rail voltage is part of AAA (Achromatic Audio Amplifier) patent owned by George Lucas.   The key of AAA amplifier is not only modulation of the rail voltage, but also elimination of looped (recursive) feedback by adding second parallel "error" amplifier that corrects the output by subtracting the "error" form the output value (two sets of output transistors), completely eliminating TIM distortions.   

Perhaps in BASH and class H power supply voltage is modulated with different time constants, but I don't see any sonic benefits of either scheme.  It is used only to minimize power losses.  I believe that BASH was intended for subwoofers. 
When I was a 12-14 year old kiddie (early 1990s) with the seed of audiophilia inside of me - though not to be realized for another several years - I still cared about audio reproduction enough to realize some things sounded better than others. E.g. CDs dubbed to those Maxell high bias cassettes sounded relatively wonderful. And the Panasonic boomboxes with BASH label on them sounded a hell of a lot better than any other comparable boxes at the time ;)

As far as voltage rails following the signal, I thought that’s what the Sunfire amps did to achieve their massive power ratings without equally massive heat sinking? Now ironically, the Sunfire Signature II 600 amp I had some 13 years ago still stands as the worst sounding amp I’ve ever owned (I think the old Panasonic BASH boombox was better).
They are similar in functionality, but BASH is a bridged topology and Carver's is not. BASH claims theirs is better, lower IM distortion, but it could have been also to get around patents.
mulveling589 posts10-30-2019 6:41pm
As far as voltage rails following the signal, I thought that’s what the Sunfire amps did? Now ironically, the Sunfire Signature II 600 amp I had some 13 years ago still stands as the worst sounding amp I’ve ever owned.

@kijanki : the AAA circuit is just the feed-forward topology invented by Peter Walker (of Quad fame) back in 1976! He used it in the Quad 405 and later amps. I have a 405 in my collection. It is an excellent sounding amp (90 wpc)!