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Old 20th September 2012, 11:20 PM   #1101
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George, with loudspeakers that is another story. I use the Klippel and Praxis since they came out. I can show you that a very well designed speaker has distortion under the audible threshold. Bill Waslo and i designed a distortion isolation test that put the original signal in one ear with headphones and the distortion residuum in the other. With well designed speakers i could hear NOTHING in the distortion channel because of masking.
Switching out the music on the undistorted channel i could hear something. Audio magazine even put out a CD with my measurements. An altogether harder problem is dynamic range and bandwidth, in speaker that is. Using the Klippel i got that distortion down by 10dB the last 10 years.
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Old 20th September 2012, 11:24 PM   #1102
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Here is the distortion measured at 1 Pascal on the midrange of my private speaker.
Between 200Hz and 5KHz it is under 0.1%, better then many tube amps.
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File Type: png dist cell.png (44.4 KB, 279 views)
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Old 20th September 2012, 11:27 PM   #1103
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1 Pa ( Pascal ) is 94dB sound preasure.
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Old 20th September 2012, 11:29 PM   #1104
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The distortion isolation test :Distortion Isolation in the Time Domain
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Old 20th September 2012, 11:37 PM   #1105
RNMarsh is offline RNMarsh  United States
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In the context of designing an opamp circuit -- which tests will best seperate them and determine weaknesses and in the end, which design is the better one? Or which combinations of tests will determine which is the better circuit? This knowledge can drive the design. Thx - RNm
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Old 20th September 2012, 11:48 PM   #1106
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Here are the dynamic measurements i did on an INA i constructed with 2 AD797 and 1 LT1648 for MC cartridge head amp purpose.
Watch the scale, the resolution limit is at -150dB. This is done by gain ranging two 24Bit AD/DA converters. The measurement are pretty astounding and the sound i got was very good. I can do better though subjectively with designs that measure still very good but not as well.
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File Type: jpg Goldstandart TIM noise method.jpg (95.8 KB, 269 views)
File Type: jpg Goldstandart Belchertest.jpg (122.4 KB, 266 views)
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Old 20th September 2012, 11:49 PM   #1107
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Here is one more. I even called it "Gold standard" because it measured so well.
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File Type: jpg Goldstandart TIM squarwave method.jpg (99.2 KB, 245 views)
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Old 21st September 2012, 12:15 AM   #1108
fas42 is online now fas42  Australia
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Quote:
Originally Posted by RNMarsh View Post
In the context of designing an opamp circuit -- which tests will best seperate them and determine weaknesses and in the end, which design is the better one? Or which combinations of tests will determine which is the better circuit? This knowledge can drive the design. Thx - RNm
My personal feeling is that it will be the one that has the best rejection of noise and interference by the very nature of the topology. Obviously PSRR is a prime culprit to be investigated, but what about throughout the rest of the circuit: if the circuit is poorly executed by a DIY'er and can easily pick up stray signals, couple with extraneous influences, then how many weak spots in this, theoretical design, sense, occur through the circuit at the various junctions of the parts?

Frank
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Old 21st September 2012, 12:19 AM   #1109
gpapag is offline gpapag  Greece
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Quote:
Here is one more. I even called it "Gold standard" because it measured so well.
Hi Joachim
What does this measurement show?

And I wasn't meaning loudspeaker testing.
Thanks for the link Distortion Isolation in the Time Domain

Regards
George
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Old 21st September 2012, 12:20 AM   #1110
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by Joachim Gerhard View Post
Here is the distortion measured at 1 Pascal on the midrange of my private speaker.
Between 200Hz and 5KHz it is under 0.1%, better then many tube amps.
very nice results --- Do you have data on other speakers/drivers that are as good? Such as, one of my favorites I drag out every so often -- The New Quad electrostatic speakers? I understand they re very low distortion full range speakers. My reference speakers for very low distortion and very flat response.
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