Fantastic new audio amp !

I bet it did. The technology did not exist to build these things at a reasonable price even a decade ago. Maybe if you had BJTs made from resublimated thiotimoline. ;-)

Best regards, Spehro Pefhany

"Fantastic" as in "a fantasy?"

Thanks, Rich

That 400W amplifier was around 1975-ish, for the neighbor kid who I tutored in Algebra, applying a little bribe... get "A" and we'll build you a 400W guitar amplifier ;-)

He got an "A", and I got a swimming pool for around 1/2 price... his father was president of Anthony Pools ;-) ...Jim Thompson

Yep. They say 100W "peak power" output, which of course means nothing at all.

It's the same hyperbole many companies release today... they may well have some improvement that make their amplifiers a bit better (notice that nowhere to they talk about something as simple as the power *efficiency* of their designs), but they have to come up with all sorts of hype to get anyone to pay attention... or so they think.

The whole "use a low voltage except when you start getting peaks at which point you switch on a boost converter and have it track the peaks" is well-known (and pretty obvious to anyone "skilled in the art") technique for high-power RF amplifiers; I have to imagine the audio guys have known about such things for decades too.

---Joel

Simply put, audio signal has Gaussian distribution of amplitude. Providing ~12dB backoff for peaks, for the same max. output swing, the average audio power is going to be somewhat 1/8 of the undistorted sinusoidal RMS power. So, there is little advantage in sustaining high power at sinusoid, however the amp should be able to handle peak loads. This allows for saving $$$, especially as audio market is VERY sensitive to cost. The consideration applies to linear amps and Class D as well, because the efficiency of Class D is not so good at low power.

There are, however, quite many folks who like to drive amps deep into clipping and all that matters is loudness. If the amp is overheating, it turns down the party. The amps for those folks are rated in watts per dollar, and they should sustain full swing square wave operation. This is entire special area and the design approach is different.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

"Power efficiency" is politically correct way of saying "saving on the heat sink metal".

Audio is very sensitive to cost; lots of different things could be done, however the art is about getting it cheap and simple while keeping reasonable performance.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Unfortunately (for my ears, at least) the width of the distribution has been narrowing quite a lot over the past couple of decades. A great many commercial CDs being released these days have very little dynamic range - their peak-to-average ratio has been squashed down into a paper-thin wafer. It seems to be that the "race to be loudest" (on average) has won out over any sort of dynamic range or expressiveness.

It's even worse if you're listening to music on the radio... most stations take the already-squashed material, and squash it down even further.

Audio amps designed to play this sort of music will have to deal with a regime in which they just won't see significant changes in output power level over time, unless somebody actually grabs the volume control knob and twists it.

would be=20

Pretty much. For those old enough it seems a lot like the return of PMPO. And the other amplifier appears to be class A instead of class D.

would be=20

The target audience may be people who are dissatisfied with how loud their mp3 players get.