perceptible audio distortion

Depends on the enviroment, and a great deal on how you specify distortion

20% in a supermarket 30% in a swmming pool 110% Parliament/congress

martin

I believe from my days at Nakamichi that the level is in the neighborhood of 6% or so. Obviously, it is measureable at levels much less than this, and quite often, easily obtained.

Why do you ask?

Since you've been asking about biasing your amp, are you hearing a 'raspiness' at low levels? That could be classic crossover distortion. The way I used to adjust on the bench (long ago) was to run 30kHz into the amp at a low level of 1 or 2 V p-p into the dummy load. Watch the output on the scope and advance the bias until the 0 cross notches go away. You'll find that happens close to the 20 mA Phil Allison mentioned earlier.

Many assume the distortion increases with signal but I haven't found that to be the case. Of course at clipping all bets are off and depending on program material may or may not be annoying. The other classic annoyance is the crossover notch. Keep in mind it sounds a LOT like a rubbing/sticking voice coil. Also, some old opamps have crossover problems as well.

G=B2

It depends on cross-modulation and transient intermodulation more than raw THD.

Since I played in an orchestra, clarinet right in front of the oboe, bassoon and French horn, I go bananas on a Mozart woodwind ensemble, with nearly immeasurable THD numbers, because I can hear the beat note :-(

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
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Obama the liar...

http://politicalticker.blogs.cnn.com/2008/07/23/obama-incorrectly-claims-membership-of-senate-committee/

"Glenn Gundlach"

** Really ?

Maybe only the uA709 with zero bias on the output followers.

..... Phil

My immediate thought was the TLO-74, but I'm not sure why. Probably some piece of crap I had to repair in my earlier years....

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Hide quoted text -

So Jim, When / If you get a chance, the famous song: Streetbeater (Quincy Jones), better known as the Sanford and Son TV theme song...

Is that a big barritone sax booming, or a mic'd harmonica? My brother said it was the latter (and he's a professional musician), but I honestly don't know. It's not the sort of sound you hear very often.

-mpm

"mpm" "Phil Allison"

My immediate thought was the TLO-74, but I'm not sure why. Probably some piece of crap I had to repair in my earlier years....

** The TL07x series has no crossover distortion problem.

Would not be one of the most popular IC op-amps in pro and consumer audio if it did.

..... Phil

T

if

Oh yeah. Now I remember. I think it was a BGW guitar amplifier.

One of the worst designs I ever had to repair!!. Right next in-line to the Motorola Starpoint (microwave transmitter), the NovaBeam TV, and a little known Litton inertial navigation system, oh, and a Pagecom low-band pager.

In that order. Actually, you can move the NovaBeam to the head of the line. :)

"mpm" >

Oh yeah. Now I remember. I think it was a BGW guitar amplifier.

** BGW have never made a guitar amp.

Yawnnn......

.... Phil

You mean, like they never made this one?

Item

Note the application. And the nice guitar border the seller is using to advertise the amp.. It must really be cool to be like you and know everything.....

Double Yawnnn!!

Wow. Better not tell Adam Clayton (Bassist for U2). Looks like he uses a lot of BGW amps.

I will assume that you've read all the other replies and not repeat the good points there.

Perceptible can be hard to define. At small levels of distortion, music sounds "different" but it is hard to put your finger on what is different about it. It can sound like it is louder than you would like it to be or perhaps like something weird has happened to the high end of the frequency response. These things are very subjective and vary a lot with the type of music etc.

At something like 5% many people will say "This is distorted". It starts to become obvious that it is distortion that is what is different.

Below 5% people can hear the difference if you switch back and forth between distorted and undistorted. Depending on the details of the type of distortion, most people can hear down below 0.1% distortion.

An output stage with cross over distortion and enclosed in a feedback loop makes the sort of distortion that is most easy to hear. When a low frequency signal causes the output to cross through the dead band of the cross over distortion the output does something like this:

Ascii art:

=2E....................**........ =2E..........**.....**........... =2E..........*.*..**............. =2E..........*..**............... =2E..........*................... =2E..........*................... =2E..........*................... =2E..........*................... =2E..........*................... =2E.....*****.................... =2E...**......................... =2E.**...........................

**.............................

This produces a large amount of some of the higher harmonics of the low frequency.

[snip]

I never watched Sanford and Son. Where would I hear a copy of said tune?

That should certainly be differentiable, unless the recording is terribly mushy.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
                    Democrats, the party of NO

cy

id

I found a free streaming verion on-line, not the best quality but... The instrument in question plays the last note of the song, and also occurs near the beginning, in the second phrasing, about 4 measures in.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.theconsensus.org/ - A UK political party
http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff

'Distortion' is a catchall term, so the simple measured number doesn't correspond to a perception in a reliable way.

There was an old experiment (by Carver, reported in Stereo Review, if I recall correctly) on crossover notch distortion, which is a kind of harmonic distortion, in musical rendition (musical instruments all generate harmonics, so the distortion is 'hidden' in this case). They found perception was reliable at 1.5% measured distortion. They also found that listeners didn't object to this as hurting the music, but DID have some response to 'clipping' distortion (not sure how much).

The race to make lower distortion numbers is a marketing scam. Below

0.1%, it's unlikely to matter to a music listener. Bass distortion in most integrated circuit amplifiers is VERY high, and few complaints are heard. Have a look at the LM380 data sheet.

On 25 jul, 01:17, snipped-for-privacy@gmail.com wrote:

As others explained, it depends on the circumstances. I do not see myself as 'general public' but there is a 'get used to distortion' factor too. General public has been exposed to PWM class D cellphone songs.... give it 10% and they still like it. I bought some cheap Chinese boxes (well 150W or so each), those have those piezo tweeters in it...and when I switched those on, the sound was horrible. It is the 2 rear channels... so anyways I am used to it. When I did put the Senheiser headphones on last week, it felt like a relief not to hear those terrible tweeters. So not only amp, but also speakers, and of course source material. Way back, I think it was in the seventies, playing vinyl, Shure M44-7 element, my own designed pre-amp, huge boxes, listening for that fine detail, elliptical stylus??? Digital came, 44.1 kHz sampling CD, and after that mp3 compression, cellphones.... As others mentioned, cross-over is horrible, especially as it sticks out on low volumes, clipping is a speaker killer, and somewhere in between zero and max undistorted sine waves, something should work. Anyways, was just reading about some artist, Neil Young, making a case for better audio.... It is the whole chain however, and few have the quiet living room or workspace even to listen, for those the 80dB signal to noise is of no use, on the contrary, we need companders so we can listen in the car, or next to the PC. And with constant high volume, crossover is not so noticed, and saves current ;-) Conclusion? None, let the super hifi audio freaks have their 96kHz sampling, what not. 'General public' being converted to AAC, mp3, mp2, electronically processed stuff in many ways..... All depends what you want to do, remember listening in a church to some Quad electrostats as monitor for some flute concert, got all excited, was much younger then, could actually hear 18kHz, and all those

15625Hz TV whistles, could even tell you if a TV was synced properly....without looking. The average population gets older (grey), and those high frequencies are now used to scare away youth that hangs around, to make secret ring tones in class that the teachers cannot hear, and against insects and small mammals... Maybe older ones get deaf too (has not happened with me yet), and you need more and more power.. if the distortion is low enough they won't hear it ;-)

The largest contributor to measurable distortion in a playback system is probably still the loudspeakers, which from memory can still run consistently above 2% for a single harmonic.

RL