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Old 24th March 2010, 11:39 PM   #1121
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Default Lme49990

Joachim, here is another candidate for lowest noise & lowest THD: the LME49990.

THD < 0.00002 at 20kHz, PSRR > 100dB at 20kHz.

Blows your mind.

http://www.national.com/ds/LM/LME49990.pdf

jd
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Old 24th March 2010, 11:48 PM   #1122
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I have seen that. PSSR is amasing. When you think you have found a good OP amp another is showing up quite soon recently.
Athough National fired a lot of famous designers recently there seems to be an infinite number of substitutes on the free market.
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Old 24th March 2010, 11:52 PM   #1123
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Here is the circuit and some pictures of the Rbb setup and parts for the RIAA encoder.
Attached Images
File Type: jpg Rbb measurement setup.jpg (638.2 KB, 357 views)
File Type: jpg Parts for RIAA Encoder.jpg (601.4 KB, 341 views)
Attached Files
File Type: pdf McCormick rbb` measurement set-up.TSC - TINA.pdf (53.7 KB, 77 views)
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Old 25th March 2010, 12:01 AM   #1124
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Default Lme49990

Hi Joachim, Jan,

I'm gonna order a few LME49990 and make a nice little amp with them and will post my result when ready.

Thanks for the info!

Best regards,


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Old 25th March 2010, 12:07 AM   #1125
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Thats fine. They come quicker then i can purchase them, not to mention build anything.
We could organise a shoutout at Jan. AD against National.
Anyway, the way i use the AD makes distotion so low ( shunt feedback) that audible differences will be very small. I have not studied the National enough if it can drive a feedback resistor lower then 600 Ohm. In that case, using the Phonoclone topology you have to burn a lt of amplification in a resistive devider.
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Old 25th March 2010, 04:21 AM   #1126
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Default RIAA encoder

This is the RIAA encoder i will make.
Design is by the trustable Burkhard Vogel.
I will select the parts as good as i can and will do some quarewave measurements to my latest designs.
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File Type: pdf RIAA encoder Design Burkhard Vogel.TSC - TINA.pdf (53.2 KB, 140 views)
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Old 25th March 2010, 04:24 AM   #1127
Salas is offline Salas  Greece
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Is that from Sound Of Silence?
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Old 25th March 2010, 06:18 AM   #1128
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Yes
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Old 25th March 2010, 06:32 AM   #1129
Salas is offline Salas  Greece
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You would need super exact capacitors and resistors so to have any tight tolerance curve check meaning. Tough without a lab grade calibrated bridge to select. It can simply compound with de-emphasis tolerances and even out or boost a curve trend erratically, If it does not have seriously better selected components than what it feeds. Maybe it will be practical to tune it against a text book Riaa emphasis curve graphically on the FFT than to be sure about parts values. Just an idea.
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Old 25th March 2010, 07:40 AM   #1130
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Usually i work with a mathematically generated curve in my DAAS analyser.
This is not awailable at the moment out of known resons.
I selected the parts by using 0.01% reference resistors and 0.1% reference caps.
My bridge shows values that are 99.9 kOhm for a 100kOhm resistor and 9.9nF for a 10nF cap. I interpolated the values and trimmed with 1% silver mica. That is the best i can do at home. Lets see what happens because the mathematics of the Self RIAA are indisputable.
I am planning on an aditinal balanced input for The JG Self.
The topolohy is an inamp made from Op amps.
I made the resistor values as low as i could to avoid noise. The LME49990 can drive 20mA clean so with the choosen values i get 3V max output. That is ample for a Pre-Pre.
Noise should be around 1.4nV / qHz
Attached Images
File Type: jpg Anti RIAA.jpg (662.5 KB, 324 views)
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File Type: pdf Bal Input for JG Self.TSC - TINA.pdf (47.8 KB, 88 views)
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