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Old 12th November 2012, 12:37 AM   #29221
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Default Music for Blind Listening Tests

Yesterday, I listened to Britten's recording of his War Requiem, surely one of the highest achievements of the Recording Age. I was thinking of Mr. Marsh's assertion that he was confident of damning any small speaker in a Blind Listening Test simply from the lack of bass.

The War Requiem easily makes obvious if a speaker doesn't have extended LF. But I would no more think of using it to pick speakers as I would talk loudly when the National anthem was being played in a country in which I was a guest or defecating in a mosque. Some things you just don't do.

The fact is that in nearly 20 yrs of Blind Listening Tests, no one has brought or asked for Zarathustra, Bach's warhorse or the like when choosing which speakers they prefer. The nearest has been Ultravox's Vienna and on that occasion, the small speaker, though identified as lacking in bass, still won out.

From these tests, one might surmise, bass response is only one factor in one's choice of a speaker .. even among those who claim it as paramount.

I need to make another perhaps surprising point. The speakers which the unwashed masses 'like' in Blind Listening Tests, also happen to be the ones recording engineers, musicians, mike & speaker designers choose as 'most accurate' bla bla in the same tests. And this cuts across the favourite music of the listeners and what they use in the tests .. including stuff that has no semblance to 'real life'.

Out of this, I conclude there is such a thing as a 'good' conventional speaker and it is worthwhile striving for 'accuracy' bla bla. And that even without the Unobtainium & virgins, such speakers might still win customers and help keep you in business.

Otherwise, I would have become a beach bum far earlier than I did.
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Old 12th November 2012, 12:51 AM   #29222
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Originally Posted by kgrlee View Post
But that means you are passing your signal through 2-3x more evil OPAs Even I wouldn't do that.
But I would. Because I know what and how I want to minimize.
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Old 12th November 2012, 01:15 AM   #29223
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But I would. Because I know what and how I want to minimize.
Wave, which OPAs did you do your "Whisper Test" on?

I take it the test conditions are as you described earlier.
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Old 12th November 2012, 01:17 AM   #29224
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Wave, which OPAs did you do your "Whisper Test" on?

I take it the test conditions are as you described earlier.
All of them that I considered to use. First exemplairs were K248UD1, 140UD6, 140UD7, 140UD8, 544UD1, 544UD2, that you probably never heard of.

The last time I tested (back in 2006) all that I considered to use then as the replacement in TOA console. Particularly, 4558, 5532, 5534, 4562, opa1612. As the result, added 6k8 resistors to 4558 to bias them and left them biased asymmetrically on higher current in the console as is, but replaced opamps in summing amps by opa1612 (later, because did not have anything better then).
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Last edited by Wavebourn; 12th November 2012 at 01:26 AM.
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Old 12th November 2012, 01:31 AM   #29225
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All of them that I considered to use. First exemplairs were K248UD1, 140UD6, 140UD7, 140UD8, 544UD1, 544UD2, that you probably never heard of.
Are these Russian OPAs?

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The last time I tested (back in 2006) all that I considered to use then as the replacement in TOA console. Particularly, 4558, 5532, 5534, 4562, opa1612. As the result, added 6k8 resistors to 4558 to bias them and left them biased asymmetrically on higher current in the console as is, but replaced opamps in summing amps by opa1612 (later, because did not have anything better then).
Got schematics of the TOA you can share? Any positions with 60dB gain?

Out of 4558, 5532, 5534, 4562, opa1612, what did you find?

What microphone, preamp, power amp & speakers used in the tests?

Did you measure distortion & noise?

Last edited by kgrlee; 12th November 2012 at 01:47 AM.
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Old 12th November 2012, 01:38 AM   #29226
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I found that we Siberian bear farmers use our wit instead of huge investments.

Microphone, power amp, and speakers were used my Wavebourn prototypes.
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Old 12th November 2012, 02:24 AM   #29227
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Did you measure distortion & noise?
Good guess, about distortions. All answers are on graphs in datasheets. Particuarly, THD+N VS signal level, and gain/phase VS frequency. Hint: how much feedback would you get on 20 KHz for 20 DB gain? How much would you get for 60 dB gain? How much low level distortions will be reduced by feedback on high end of the band in question?
What is interesting, thermal induced change of low level distortios, especially on higher frequency of the interest.

I played a lot with with opamps and opamp topologies since 1970'th when I was young and infected by belief that vacuum tubes are obsolete and opams are final answer for all questions.
It was in laboratory of thick film ICs of Institute of Semiconductor Devices.
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Old 12th November 2012, 02:52 AM   #29228
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How much would you get for 60 dB gain? ...
...I played a lot with with opamps and opamp topologies since 1970'th
Trying to set them at 60db gain ? Congratulations.
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Old 12th November 2012, 03:32 AM   #29229
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I tend to use 2 op amps in a multiloop configuation for that much gain

Gerald Graeme has also advocated 2 op amp composite amplifier, with high loop gain from 2 pole responses – his “Amplifier Applications of Op Amps” 1999 devotes a chapter to composite op amp circuits and their compensation
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Old 12th November 2012, 05:33 AM   #29230
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Trying to set them at 60db gain ? Congratulations.
However, we Siberian bear farmers are stupid and ignorant guys; we are so stupid so instead of taking baths and using perfume we wash out bodies in steam baths slapping them by birch brooms. But at free from slapping bodies time we sometimes used to design opamps, optimize them for different applications, used them for different filters, non-linear converters, control systems, and so on. However, you would never believe that because it is impossible...
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