Luckily today we have the benefit of good simulators, mathcad etc which can really help develop ones understanding of feedback ( and other stuff) very quickly. I know that climbing the learning curve without these tools no doubt took much longer. That said, there is also no substitute for burning ones fingers with the soldering iron as you try to stabilize an errant amplifier.
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This is somewhat paradoxical, but I think true. All distortions are not created equal, and the observation that loudspeakers have a lot of one sort or another should not provide an excuse to neglect improvements in other areas.
Two ears and a brain are remarkably adept at sorting things out. For example, one of the most surprising aspects of listening tests for loudspeakers that's come to light recently, in carefully controlled experiments, is the degree to which listeners' preferences for loudspeakers persist in even "bad" rooms.
Closing the loop(s) in a system, however, I think is a promising way to go. Most of the approaches I've seen tend to focus on flattening the on-axis frequency response, which in isolation is a good thing---but unless the directivity index is well-behaved, can actually make things worse. Of course there is a brisk business in room correction boxes, but they can't fix poor off-axis behavior.
The problem of course is that in high end activities, devotees wish to mix and match. If you bundle the electronics with the loudspeakers this interferes with that pursuit. I have opined to a couple of people still at Harman that I think it was a marketing mistake to insist that the M2 be sold with amplifiers, regardless of how good they may be.
For lower-overall nonlinear distortions, some positional-motional information could be helpful if used right. And it should not be approached as just a way of fixing a bad transducer, any more than global feedback be used wholesale to correct for a lousy open-loop amplifier.
Nonsense John.
Buy the LTSpice book from Jan and go through it.
There are lots of systems out there today that could not have been developed cost effectively or at all without simulation tools - think aeronautics, chemical engineering, construction, semiconductor processes, drug development etc. Electronics is no different and simulation helps you explore subleties that would otherwise go unnoticed or misunderstood. It also makes trying new ideas a whole lot easier.
That said, you do of course need to have a good grasp of the fundamentals - you are otherwise just shooting in the dark.
+1
Which everybody here knows damn well, it's just that this argument is about as near as some of us get to a conversation. If it floats your boat...
After a look around, I stumbled upon another young chap, Niko Petro, from the same area - he references Kolinummi. He just did a thesis recently on "Modernised Current dumper audio amplifier", https://dspace.cc.tut.fi/dpub/bitstream/handle/123456789/21669/Petro.pdf?sequence=1 - just about all in Finnish I'm afraid, but plenty of circuits and scope shots from working units.
A short intro in English, and from that,
A bit of effort with Google translate should extract the jist of it ...
The JBL M2 speaker has been mentioned a few times, and this review is a good sign, Mix - August 2013 - First Listen: JBL M2 Master Reference Monitor. The manufacturers seem to be finally starting to get it, as evidenced by the reaction of the listeners quoted.
I ran simulators back in 1966, even BEFORE Spice ever existed. I attended classes at UCB given by the 'father of SPICE' and went through weeks of detail back in the early 70's. Still, I found that for audio, it was not the easiest way to make successful products. Perhaps more complex systems would be OK.
I have LT SPICE, and so what?
I have LT SPICE, and so what?
The fact that Apple hired Tom Holman (THX, Apt, Advent) might seem to indicate otherwise. We'll see.
Kindhornman, those "couple of parts per million" distortion artifacts are the wrong things to measure - I find it trivially easy to get an amplifier to audibly misbehave, by giving it an electrically unpleasant environment to work in, and feeding it the right material to amplify - just because a car can do a 150 mph doesn't mean it's not a death trap to ride in at normal speeds.
Kindhornman, we still have to look at improving analog electronics, no matter how well it measures in the conventional sense. There are still differences I cannot explain, and nobody else can either, (yet).
For you to tell me about feedback when you don't even know calculus, is really surprising. Of course, Bob's book does not include calculus, but don't think it that isn't important to understand processes like feedback at a deeper level. Without calculus, I don't know what I would do. Perhaps repair electronics.
For you to tell me about feedback when you don't even know calculus, is really surprising. Of course, Bob's book does not include calculus, but don't think it that isn't important to understand processes like feedback at a deeper level. Without calculus, I don't know what I would do. Perhaps repair electronics.
> There are many amps with ever decreasing distortion,
> a couple of parts per million, the final frontier is the end
> of the chain, the speakers.
Agreed ..... BUT ! ..... The rattiest speakers (within reason)
will not conceal perceptual amplifier differences.
In the same way that with 100 op amps in series, the 100th
degrades the signal as much as the 1rst by itself.
> a couple of parts per million, the final frontier is the end
> of the chain, the speakers.
Agreed ..... BUT ! ..... The rattiest speakers (within reason)
will not conceal perceptual amplifier differences.
In the same way that with 100 op amps in series, the 100th
degrades the signal as much as the 1rst by itself.
John,
I don't think you need to know calculus to understand feedback. Do you need to know materials science to understand how a transistor is working? I did have the notion at one time that feedback must be wrong until I read Cordell and Self and others on the subject and saw the errors in my understanding. I bet you couldn't do many things I find simple, that doesn't mean I couldn't explain them to you in simple terms you would understand. I respect that you have more than a simple understanding of many things in electronics and are ahead of many others in your field. I'm not sure I would go to you though to do design work on the digital side of things and you do know calculus, so it is a lot more than simply knowing some mathematics.
hitsware,
Agreed.
I don't think you need to know calculus to understand feedback. Do you need to know materials science to understand how a transistor is working? I did have the notion at one time that feedback must be wrong until I read Cordell and Self and others on the subject and saw the errors in my understanding. I bet you couldn't do many things I find simple, that doesn't mean I couldn't explain them to you in simple terms you would understand. I respect that you have more than a simple understanding of many things in electronics and are ahead of many others in your field. I'm not sure I would go to you though to do design work on the digital side of things and you do know calculus, so it is a lot more than simply knowing some mathematics.
hitsware,
Agreed.
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