TAS5706

[bcarso]

Scanty details on this "digital" amp so far regarding the output stage correction circuitry that reduces power supply noise. Anyone know more?

 

[Rochey]

For all intents and purposes, it's a closed loop amplifier. Normally, most class D amps are open loop, meaning any noise on the power supply will get coupled into the output. (as class D essentially switches the power supply into the speakers multiple times a second).

By having integrated feedback, the noise of the power supply gets rejected.

Open loop amplifiers require power supplies that are superior to those required for closed loop. (superior supplies = $$)

/R

 

[bcarso]

I'd still like to know how the loop is closed---evidently, according the the blurbs, it is confined to the output stage, as opposed to some other schemes. [ EDIT: That is to say, the question is not why, but how.] The PSR with frequency didn't seem to be shown, although there was a remark about 120Hz rejection improvement over open loop, and the important distinction about measuring with a signal and load compared to what most do at zero signal.

I may have remarked in here that I was negotiating a few years back with TI to do some interim hybrid design while the European team worked on a next-gen higher-power digital modulator system. We deadlocked on price, but before that got obvious I had hinted at some approaches to doing a form of PS compensation. Not that I am claiming those ideas were lifted. What may be greater issues are possible conflicts with some of Gerald Stanley's recent patents.

But then the switchamp arena is a minefield for IP.

 

[JohnRoberts]

I have seen class D where the loop is closed around the output stage.

some discussion here.

http://recforums.prosoundweb.com/index.php/m/326030/22399/0///361/#msg_326030

This is not your old school PWM with triangle wave and comparator. The lag from the output filter determines the amp switching rate.

JR

 

[bcarso]

Yeah, that's basically Bruno Putzeys' uCd, and it works very well indeed. I was told NXP/Philips will let anyone use it if you agree to populate with at least some NXP silicon.

Don't use the H* word with the Hypex folks though---they seem to be unduly sensitized.

But the TI beast is clearly a digital modulator-based amp. They don't seem to want to talk about the details of how the output stage correction is done. Perhaps it is still in patent purgatory.


*heterodyne---the toplogy is inherently variable frequency, thus can be prone to artifacts in multiamp systems.

 

[bcarso]

Here's a nice little story about Bruno I just found:

http://spectrum.ieee.org/feb08/5924

I have to smile about the significant other in...Rwanda :roll: