Why Is High Feedback Considered Bad In Audio? In Simple Terms

Yup, high-end audio is mostly a useless waste of money, but at least it's not outright harmful like cigarettes or opera tickets.

John

On Fri, 23 Jan 2009 16:24:45 -0800, "Bob Eld" wrote:

Some classes of higher-order filters ring, some don't at all. More math.

Ringing can be a linear phenom, in which case it's just peaking in the frequency domain. And if the ringing is above 20 KHz, there's nothing to peak and nobody can hear it anyhow.

John

I'll have to add "grittiness" to my list of audio metrology terms...

5N, 6N, 7N (as in 99.99999 pure copper) acceleration agressive air articulation bass transient response blackness bloom bright burnin (cables) clarity color confused congested continuousness crisp delineation of inner detail dynamics effortlessness etched extension fast bass free-flowing ease grainy granularity hangover hard harmonic completeness hashy holographic honesty impact jump layering liquid liquidity liveliness lush macrodynamics microdynamics musicality openness pace quantum purifier reference refinement relaxed roundness reveal single-crystal copper slam slow bass smear soundstaging space sparkle effect spatial resolution speed stunning (everything is stunning) thin tight tight (bass) timbre tipped-up transparency truth unfussiness wire direction

Orrrff?

John

Wait, you mean my 99.99% oxygen free monster speaker wire won't help me?

"

You left out "warm" ;-)

...Jim Thompson

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4N wire? you can barely make out the lyrics with 4N. You need 6N or 7N purity for serious audio. Preferably cryo-treated single-crystal.

John

Well, yes, but selling a few silver wires and gold plated CDs to people is hardly in the same league.

Sylvia.

I'll add it. Is that measured with a thermocouple?

John

If you want the mere 40dB of feedback at 20 kHz, then the amp should have enough of phase margin at 2 MHz, which is not quite so simple for the power BJTs operating at the high levels of injection. The optimization of the multiple feedback loops for the worst case operation requires careful approach. The other thing about audio is that it is severely constrained in the cost. That means el cheapo transistors and the single layer PCBs with the split grounds :-)

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

How about "parasitic randomization of phase characteristics" or "nonlinear impulse response" ? I read it in the magazine, can't figure out what it is supposed to mean.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

I thought in reviews of hi-fi essentials like anti-vibration CD player mounts and oxide free copper mains leads a statement along the lines of "even my wife could hear the difference" was mandatory.

There were a few things in older transistor amp design that weren't done well, and the lower feedback designs were more tolerant of these things. Besides the Doug Self papers in Chris Jones post, dig up the old Marshall Leach papers.

If I were to roll an amp together, I'd be more inclined to go for linear MOS on the output. Randy Sloan's amp book is a good reference, even if you only want to read about such design.

No, once the wife hears where the $1000 goes, all fidelity is lost.

In many ways they're worse.

Unless the rent money goes into 5N copper.

If one were going to go after purveyors of that kind of gear, then for consistency, one would also have to go after a large part of the entire cosmetic and beauty industry. In common with the impugned audio equipment vendors, they too are at best selling people the means to delude themselves.

Which is not to say that would be a bad thing, but it illustrates the true scale of the problem.

Sylvia.

And of course, there's the problem that when the wife hears it, she knows what's expected, and says "wow!" The audiophile then listens again, says "you're right" and sends it all back.

Sylvia.

Sorry, I didn't see the original post.

[...]

Google for "transient intermodulation distortion" and "Matti Otala".

""Bjarne Bäckström"" "abby"

** Might as well Google up " Lewis Carroll " and "Alice in Wonderland" while you are at it.

"The Mad Hatter" makes more sense than that blatant fake Otala ever did.

...... Phil