Nope. I'm not kidding. The first one I know was published by Norman Crowhurst. And then there's David Berning's ZOTL amps.
I, again, have to relate what I learned about negative feedback in audio from Richard Heyser.
Richard and I first met when I attended my first AES convention as a member, in LA in 1968. We both used a single K-horn to listen to quality audio, and we were both very interested in making quality audio electronics, so we became instant colleagues, for the next 15 years or so. Now, I seem to have heard statements from Richard Heyser that many of you have never read in one of his papers. At least not how I heard about negative feedback from him.
Now can you comprehend why he told me things that he did not necessarily put into his technical papers? Probably not, for many here, but it because I kept an OPEN MIND about the opinions he gave. Later, I was to test his assumption that negative feedback was problematic for quality audio reproduction, when I started making low feedback, fast circuitry professionally, and that is when I confirmed his position on feedback over 40 years ago.
Now, how did he come to hold such an opinion?
He told me that he developed an amplifier circuit that was destined for a moon mission and after getting it to work, he took it home just to see what it might sound like with his K-horn. This was years before I first met him, but he did write a paper for the AES on his amplifier (it's around here somewhere) after his listening experience.
Initially Richard did not know that the amp he designed, (when you see the schematic you will understand), would work as well as it did. It generated plenty of distortion. What was going on anyway? Well, others heard it as well and it got popular with the diy set, long ago. One guy just lifted the circuit and started making and selling it to customers. Most of us would just think it was a fluke, but a 'prepared mind' took it further. He determined that it was the 'open loop' aspect of the amp was what made the difference, and he was not afraid to tell me this, even though he apparently had just as much trouble with the entrenched establishment at the time, as Chas and I do today. That is why Richard and I could remain colleagues, we didn't call each other stupid names when something not so obvious came up. (more later)
Richard and I first met when I attended my first AES convention as a member, in LA in 1968. We both used a single K-horn to listen to quality audio, and we were both very interested in making quality audio electronics, so we became instant colleagues, for the next 15 years or so. Now, I seem to have heard statements from Richard Heyser that many of you have never read in one of his papers. At least not how I heard about negative feedback from him.
Now can you comprehend why he told me things that he did not necessarily put into his technical papers? Probably not, for many here, but it because I kept an OPEN MIND about the opinions he gave. Later, I was to test his assumption that negative feedback was problematic for quality audio reproduction, when I started making low feedback, fast circuitry professionally, and that is when I confirmed his position on feedback over 40 years ago.
Now, how did he come to hold such an opinion?
He told me that he developed an amplifier circuit that was destined for a moon mission and after getting it to work, he took it home just to see what it might sound like with his K-horn. This was years before I first met him, but he did write a paper for the AES on his amplifier (it's around here somewhere) after his listening experience.
Initially Richard did not know that the amp he designed, (when you see the schematic you will understand), would work as well as it did. It generated plenty of distortion. What was going on anyway? Well, others heard it as well and it got popular with the diy set, long ago. One guy just lifted the circuit and started making and selling it to customers. Most of us would just think it was a fluke, but a 'prepared mind' took it further. He determined that it was the 'open loop' aspect of the amp was what made the difference, and he was not afraid to tell me this, even though he apparently had just as much trouble with the entrenched establishment at the time, as Chas and I do today. That is why Richard and I could remain colleagues, we didn't call each other stupid names when something not so obvious came up. (more later)
Tee hee. Maybe an exclusive line of audio ones in gold plated metal cans @ $200 each could do the trick. Mil rated and everything. In three grades A, B, C with A commanding a premium of $100.
Grade C probably represents nirvana in 2016.
Cars? Guitars? Shoes? Nails? Baseball bats? Interstellar cameras? No.
I think your non-mil rated, plastic cased standard kit probably represents a black blob with gain......
I'm happy with 3.14. But I also understand measurements. Measuring gravity waves is phenomenal. I get the tech and finite, tiny values involved.
The negative feedback argument is very old. We can measure tiny values in 2016. A modern OP-amp is many years advanced (on an exponential curve) from even 10 years ago.
I have no problem with personal preference. Also musical expression. Also individuality.
Amplifier tech is under the microscope. Modern OP-amps are difficult to fault. Unless you use magical, karma, presence, "fluff" or some other measurement method.
The classic marketing story for high end always seems to have NASA/,military in there somewhere. Handy that...
Minus of course, all the nasty, grubby, test and validation parts that verifies efficacy and safety. 🙂
Tee hee. Maybe an exclusive line of audio ones in gold plated metal cans @ $200 each could do the trick. Mil rated and everything. In three grades A, B, C with A commanding a premium of $100.
That's not really a joke, AD8229 works up to 175 degrees (in SOIC) and costs 160 quid, in singles. That's by far the best op amp I've seen, available for the masses 😀.
AD8229HRZ Analog Devices Inc. | Integrated Circuits (ICs) | DigiKey
Obviously those oil drillers don't care about money.
Here is the schematic that Heyser published in an AES preprint in 1959. (091)
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Shhhh you could start a new craze. Imagine all those descriptions - deep, subteranean bass, fluid treble etc.
Proto is built. PCB is 98% finished. It hands down beats the pants off of the most tweaked LCRMKIII I can conjure up. Remember Bear's most recent rant about speakers disappearing and the sound enveloping the listener? This design is a big step in that direction.
It does things like vividness, micro-transients, depth, left-right AND up-down (significantly above the placement level of tweeters) imaging. All those things that can't be measured and illudes most of you on this forum.
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We can do femto-second pulses and record light propagating through space. Surely nano is old hat!
Yes, much better. That was a time of trafo scarcity. Those big red Wima's are gone now too. They were munching micro-dynamics a bit too much.Better than the one with indecent transformers? 😱
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Are we now supposed to stand in awe in front of this crap?
Yes, it sounds interesting when the voice coil pops out of the
pole plate and stays there as the quiescent state.
A quintuple Darlington, overall. Did he hope he could force it
to get voltage gain from a few stages more?
With a construction like that I understand that feedback
can never work. Since the total beta is the product of
the n betas, gain falls at n* 6 dB/ octave, with the resulting
disaster for the gain margin. Around the 180° somewhere
in the middle of the passband.
I fully accept if someone pulled the emergency brake.
I need a drink now.
Cheers, Gerhard
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