I received the book a few days ago and just now got time to start reading it. It starts off with the good old "wax on; wax off" approach. Simple but not simplistic.
The editorial reviews are in. Here is a sampling of them.
It is very readable; not fatiguing at all!
The book presents a wide, open sound stage that extends beyond its pages!
Inky black text against a pristine white backdrop - superb!
I digress. 😎
The editorial reviews are in. Here is a sampling of them.
It is very readable; not fatiguing at all!
The book presents a wide, open sound stage that extends beyond its pages!
Inky black text against a pristine white backdrop - superb!
I digress. 😎
I bet Bob's editor told him to use the word "heuristic" instead of "common sense".
Hi Chris,
I'm really sorry to hear that you have not gotten the book yet.
The most important thing that I would like reviewers to do is to measure the small-signal frequency response AS SEEN AT THE SPEAKER TERMINALS when they review an amplifier or compare one amplifier to another. I'm certainly not saying that it all has to do with frequency response, but this is a variable that may be at work in some cases and should be evaluated.
Ditto for reviews of loudspeakers and speaker cables.
Cheers,
Bob
Hi Lynn,
Thanks again for your kind comments. I did have a very good editor at Mcgraw-Hill, and they are a good team to work with. I also did a lot of self-editing. I reviewed and word-smithed the material many times, even before manuscript submission. Then came the copy-edit stage, and after that came the proof stage. I have effectively read the book many times 🙂.
With reference to the VI limiters and back-EMF, we used to refer to such amplifiers as "tweeter eaters".
Thanks again!
Cheers,
Bob
Spelling error page 18, last use of the word: "milliseimens"
What do I win? A smack in the head??
😀 😀 😀
Hi Damon,
SPICE is a wonderful tool, and really good for audio power amplifier design. However, there is a huge amount of SPICE information scattered all over the place, much of it providing great detail and zillions of options. I wanted an amplifier-centric coverage of SPICE. That's what I attempted to do in the book.
LTspice is one of the very best versions of SPICE out there, and it is free. It can be downloaded from Linear Technolgy Corporation's site. I plan to put a link on my site that goes right to the needed LTC web page.
Cheers,
Bob
Hi Conrad,
And thank you for the kind words. I take no responsibility for your loss of sleep 🙂. Indeed, my goal is that it not PUT you to sleep.
Cheers,
Bob
And to add to that, reviewers should start measuring distortion in loudspeakers instead of pretending that it doesn't exist !!
Why do reviewers go to great lengths to measure negligible amplifier distortion but completely disregard high levels of distortion in speakers ??
as far back as I can remember, reviewers do show SPL and the first two harmonics on the frequency response plot.
Sometimes the distortion is factored to allow the plot to fit the space in the column inches available.
I have a 1968 review of the Tannoy Dual Concentric and 2nd and 3rd harmonic are clearly visible. No body tried to hide it's existence.
Hi Trevor,
I also think it would be good to measure loudspeaker distortion. However, its significance to sound may be different than that of distortion from electronics, even though it may be numerically much higher.
First, I think it is generally confined to low-order distortion, and certainly no crossover-like distortions.
Second, in multi-way loudspeakers, there is less opportunity for intermodulation distortion.
This all is just speculation on my part, however.
Cheers,
Bob
That seems to be the exception to the rule rather than the rule.
Apart from the odd subwoofer shootout you rarely see distortion tests even on the most expensive speakers.
For example see this Wilson Sasha speaker reviewed in Stereophile. Stereophile: Wilson Audio Sasha W/P loudspeaker
It sells for $27,000 US but there is not one measurement on distortion.
Now if you'd paid 27K for an amplifier wouldn't you expect to know its distortion performance ?
Somehow you are supposed to ignore it in speakers, even expensive ones 🙁
Well it would be pretty hard to ignore a speaker distortion of 10% compared to 3 to 4 orders of magnitude or less in an amplifier even if the harmonics were distributed differently.
I think a distortion benchmark in speakers would be one good way of comparing speakers and sorting out the wheat from the chaff 😉
regards
Trev
Afair, there's been one since 1981.Sure, but it would be one of many tests needed to sort speakers. I also suspect that the distortion characteristic of some loudspeakers might be influenced by the (often frequency-dependent) damping factor of the driving amplifier.
Cheers,
Bob
Actually no.
If I paid $500 for an amplifier, I'd expect to see detailed technical specs.
For $27k I'd expect to see details of how the OPT is hand-crafted from carefully aged pure silver thread by a blind Tibetan monk.
It's certainly one test that speaker manufacturers avoid for obvious reasons mainly because speakers measure so poorly with regards to distortion and the manufactures know it 😉
regards
Trev
Amplifier Loudspeaker Interactions
Getting back to power amplifiers, it is important to understand that there are interactions between the amplifier and loudspeaker that must be recognized.
Damping factor is just another way of describing amplifier output impedance. The in-service frequency response of an amplifier is affected by the damping factor, and not just at low frequencies. This is largely due to the fact that the load impedance of a loudspeaker goes through big variations at the woofer/cabinet resonances and usually at the crossover frequencies. An amplifier with a damping factor of 20 (like a tube amp) has an output impedance of 0.4 ohms. A loudspeaker whose impedance changes from 16 ohms at an impedance peak to a bit below 4 ohms at an impedance dip will cause a frequency response change of about 1 dB - plainly audible.
In this regard, it is also important to unerstand that the loudspeaker manufacturer "voiced" his loudspeakers while they were being driven by a particular amplifier. Depending on the difference in damping characteristics between that amplifier and yours, the loudspeaker may sound quite different. Suppose the loudspeaker manufacturer was a guy who preferred vacuum tubes and voiced them with a tube amp, and you listen to them with a solid state amp with a high damping factor, for example.
Loudspeakers with wild impedance swings and low minimum impedances can be difficult to drive at moderate to high power levels as well, sometimes resulting in protection circuit intervention or simply inadequate amplifier output current capability. Amplifiers whose output stages are vulnerable to beta droop may be more strongly affected. The impedance of some speakers drops to 2 ohms or less, making life miserable for some amplifiers that otherwise measure well on the test bench.
Cheers,
Bob
Getting back to power amplifiers, it is important to understand that there are interactions between the amplifier and loudspeaker that must be recognized.
Damping factor is just another way of describing amplifier output impedance. The in-service frequency response of an amplifier is affected by the damping factor, and not just at low frequencies. This is largely due to the fact that the load impedance of a loudspeaker goes through big variations at the woofer/cabinet resonances and usually at the crossover frequencies. An amplifier with a damping factor of 20 (like a tube amp) has an output impedance of 0.4 ohms. A loudspeaker whose impedance changes from 16 ohms at an impedance peak to a bit below 4 ohms at an impedance dip will cause a frequency response change of about 1 dB - plainly audible.
In this regard, it is also important to unerstand that the loudspeaker manufacturer "voiced" his loudspeakers while they were being driven by a particular amplifier. Depending on the difference in damping characteristics between that amplifier and yours, the loudspeaker may sound quite different. Suppose the loudspeaker manufacturer was a guy who preferred vacuum tubes and voiced them with a tube amp, and you listen to them with a solid state amp with a high damping factor, for example.
Loudspeakers with wild impedance swings and low minimum impedances can be difficult to drive at moderate to high power levels as well, sometimes resulting in protection circuit intervention or simply inadequate amplifier output current capability. Amplifiers whose output stages are vulnerable to beta droop may be more strongly affected. The impedance of some speakers drops to 2 ohms or less, making life miserable for some amplifiers that otherwise measure well on the test bench.
Cheers,
Bob