Negative Feedback in Audio Amplifiers

Uncle Steve · 2013-02-02T02:14:21+00:00

Recently, I had the experience of re-manufacturing the tweeters in a pair of speakers I had bought. Due to a "senior moment", I fried the tweeters in a pair of Quadral Chromium Style 50 speakers, and the local dealer decided to fuck me over even though I admitted the mistake and paid for replacements. Why they decided to screw with me is another story, no doubt involving elements of the RCMP who would prefer not to be named. At any rate, I was left with a pair of drivers with unequal efficiency, and it annoyed the living snot out of me. So I decided to take the two broken tweeters and rehabilitate them. If you look into the Quadral speaker line, you will discover that the tweeters use a filament suspended between two powerful magnets in series with a 5.1 ohm resister. The filament is apparently a piece of aluminum coated with a thin layer of titanium, or something to that effect. My replacement is somewhat thinner, and required the manufacture of unique tooling to shape. The result has less mass and consequently improved the sensitivity of the driver, with obvious implications to the resultant sound quality. My amplifier is an Onkyo M282, which is apparently an amplifier that uses negative feedback, and made in Japan. On the Web, there are a number of articles which articulate the controversy over NFB amp designs, with numerous manufacturers shunning the technique for various reasons. None of the descriptions or reviews take into account the most important factor in an audio system -- the interaction of the speakers with the amplifier. I believe I have achieved such good results primarily because I reduced the "mass" of the tweeter, which in combination with the amplifier design, has helped produce a superior sound. The key to understanding the thinking behind this is the interaction of the amplifier with the speakers. Speakers are an inductive load, AFAIK, which means they present some of the same problems as electric motors in the design of driver...

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Uncle Steve 13 years ago

I think I have a reasonably thorough apprehension of the text I quote in my .sig. What do you think I am missing?

Regards,

Uncle Steve

More than a century has passed since science laid down sound propositions as to the origins of the universe, but how many have mastered them or possess the really scientific spirit of criticism? A few thousands at the outside, who are lost in the midst of hundreds of millions still steeped in prejudices and superstitions worthy of savages, who are consequently ever ready to serve as puppets for religious impostors. -- Peter Kropotkin

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Uncle Steve 13 years ago

This is a little bit like a gun-control debate. Lots of audio equipment is garbage/too expensive/whatever primarily because the people who make it are too often contemptuous of the consumer, and the consumer is also too often ignorant to understand what he is doing. In no case is it the fault of 'audio'.

Regards,

Uncle Steve

More than a century has passed since science laid down sound propositions as to the origins of the universe, but how many have mastered them or possess the really scientific spirit of criticism? A few thousands at the outside, who are lost in the midst of hundreds of millions still steeped in prejudices and superstitions worthy of savages, who are consequently ever ready to serve as puppets for religious impostors. -- Peter Kropotkin

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Uncle Steve 13 years ago

I'm not quite sure why you are so upset. I was merely temporizing, and I think most people here understand the difference between high-speed interconnects and broadcast-oriented transports like Ethernet in the context of actually building something to move bits around.

Regards,

Uncle Steve

More than a century has passed since science laid down sound propositions as to the origins of the universe, but how many have mastered them or possess the really scientific spirit of criticism? A few thousands at the outside, who are lost in the midst of hundreds of millions still steeped in prejudices and superstitions worthy of savages, who are consequently ever ready to serve as puppets for religious impostors. -- Peter Kropotkin

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Uncle Steve 13 years ago

Tarantulas are supposedly quite tame unless mishandled or otherwise aggravated. I have no meaningful experience with apples so I cannot comment further.

Regards,

Uncle Steve

More than a century has passed since science laid down sound propositions as to the origins of the universe, but how many have mastered them or possess the really scientific spirit of criticism? A few thousands at the outside, who are lost in the midst of hundreds of millions still steeped in prejudices and superstitions worthy of savages, who are consequently ever ready to serve as puppets for religious impostors. -- Peter Kropotkin

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krw 13 years ago

Ethernet-AVB

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Michael A. Terrell 13 years ago

Rationality & Audio in one sentence?

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josephkk 13 years ago

video

though

full

Since you did ask, the first sentence more than the second. It is real hard though, i fail near as often as i succeed.

?-)

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josephkk 13 years ago

feed

was

panacea

latency?

SMPTE

Word salad and worse. You are misusing "high speed interconnects", "broadcast-oriented transports" and "Ethernet" horribly.

High speed interconnects normally refers to physical connectors and connection systems, which may or may not include a protocol, and may or may not include timing constraints.

Broadcast-oriented transports include C-band satellites (microwave carriers FM modulated by the composite {audio and video} NTSC television signal); D1, many other latency controlled SMPTE standards transports.

Ethernet is all about data transport in an unreliable network, it includes reliable and unreliable transmission protocols. Pretenses of real time as well as streaming protocols were added later creating confusion about what Ethernet really is.

HTH

?-)

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josephkk 13 years ago

The threshold is nearer us $500 per component, sometimes below. Special technologies can create some rare exceptions, e.g. laser turntables, microscopic video turntables. For the rest, it gets nearly immeasurably close to the best by $300, then some feature wars, but past $500 even that is running out of gas.

?-)

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Michael A. Terrell 13 years ago

From some recent research, it looks liks TV broadcast is still 75 Ohm coax in the studio. Some Tektronix waveform monitors have both NTSC Analog & SDI Digital loopthrough inputs (1730 series). That allowed stations to continue to use the same equipment as they converted to digital. I recently picked up two 1730 for $20 each for my home shop.

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josephkk 13 years ago

or

television

includes

time as

what

Shazzam. That is a good score.

?-)

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Michael A. Terrell 13 years ago

I also bought a Tektronix NTSC Television Sync Generator TSG170A for $15, + 25 shipping, a Grass Valley 8500 cage with power supply, and some

8501 & 8502 video DA cards for 99 cents plus shipping. The 9" Ikegami TM9-3A color monitor for $10 was a sweet deal, too. 4:3 or 16:9. :) I could build a small VHF amp (100W) for the $10 Blonder Tongue Agile modulator and have an analog LPTV station.

All of this gear is better than anything I used at any TV station I've worked at, and it's selling for under a penny on the dollar. I wish I had had this stuff on my bench when I was repairing C band sat gear. I have the perfect rack for it too. It's blue with a Tektronix logo on it. :)

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John Larkin 13 years ago

Tell that to Netflix!

John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

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Negative Feedback in Audio Amplifiers

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