> these are not referreed journal submissions
Today's aX offers at least three examples.
Nelson Pass is playing with high-Z amplifiers, damping factor like 0.1. That would raise eyebrows on the peer committee. True, it does not change the midband, and the slope in the treble can be designed-away in the speaker (or a zobel...). Quite interesting bass is possible in large baffles or in horns (another of Pass' toys). I think the killer flaw is that a hi-Z amp does not allow the small-box speakers, AR-3 et al. For the same flattness, efficiency, and F3, the hi-Z amp will always need a larger box.
The Ω pipe speaker article is interesting. A factor of 10 is pulled from thin air and locked in stone without examination. The result may be more an extended vented box than a pipe. It does take a given speaker deeper than is practical in a vented box, but the F3/size/efficiency factor is like a vent-box. Oh, he stumbles over the Fs/Qts ratio but does not notice that Fs/Qts is a key parameter for a speaker driver.
And those darn PA horns. Lot of hogwash theory. LOT of time in the woodshed. I must admit his results are interesting. The current one gives a horn-gain that hits or beats what I would expect from perfect horns that size. It "beats" because he's getting a huge amount of directivity, boosting the on-axis and near-axis SPLs. It would be interesting to see total-output and Q figures. But to come anywhere near a perfect horn, in a box that size, with construction that is darn difficult but not insanely so, shows that he does not take his hogwash theories too far.
I shouldn't get started on the Line Amp essay, except to note that the current source will NOT "begin to pump current at power-on", and you do NOT have to let the tubes heat before applying B+. It is NOT a "current source", it is a current limiter, and can't "pump current". Argh.
Oh, the article on digital amplifiers surprised me. It is a TI-written puff-piece. I don't mind that: cutting-edge work like this often comes out of commercial labs and who else could write it up as well? But in this case, where's the beef??? Technical information is just a pretty picture and some pretty words. I know exactly how their new scheme differs from the common "digital" amplifiers; I invented the plan a decade or two before it was practical. But the article does not explain actual operation even at dummy-level. I think TI should have been charged ad page-rate for most of that piece. And they probably have better text right on the chip-series data-sheets. I know I've seen a plain-text tech-explanation somewhere, maybe from the days before TI ate the patents.
> When OTOH some arrogant a**hole holds forth, for example in Electronics World
In recent years, Wireless World et seq have fallen on hard times. They don't have revenue so they can't pay, and have to take what they can get.
> the time that an rf engineer decided to enlighten us about how IM distortion was what we stupid audio folk should be measuring
I recall the article and, ignorant as he is, the RF racket's tests are a useful way to think about audio. 2nd order and 3rd order intercept, and 1dB compression, are valid for audio amps with simple nonlinearities. Multi-tone missing-bin IM testing may be a very sensitive test of complex flaws that our ears hear.
