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Question: Cheap pure sine wave genertor 1khz?
Gyro:
--- Quote from: innkeeper on January 10, 2020, 09:57:22 pm ---
--- Quote from: Gyro on January 10, 2020, 10:49:03 am ---There are assembled versions available on ebay too, but populating one of these bare boards with genuine components (and maybe lower distortion opamps) ought to get you close to what you need. It uses a J-FET for amplitude control. Jim Williams found that there was some channel resistance modulation when using a J-FET, that could be trimmed out with a little local feedback [Analog Circuit Design - Art, Science and Personalities, Chapter 7 (Max Wein, Mr Hewlett and a Rainy Sunday Afternoon)].
You might get better than the quoted -124dB with some careful component value matching anyway...
https://www.ebay.com/itm/Low-Distortion-Audio-Range-Oscillator-1KHz-Sine-Wave-Signal-Generator-PCB-Board/262844562138
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i've actually ordered one of these .. figured its a start and maybe i can tweak it. i was thinking of just replacing the tl071 for something quieter. i didnt know aout that article, i will defiantly try and find it ... i figure it would do until i can make or get somthing better. like vidnic's on diyaudio...
i;ll look into that article if i can find it.
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A good start for sure.
RoGeorge actually found an online copy of that chapter - he linked it above.
innkeeper:
--- Quote from: Gyro on January 10, 2020, 10:49:03 am ---Jim Williams found that there was some channel resistance modulation when using a J-FET, that could be trimmed out with a little local feedback [Analog Circuit Design - Art, Science and Personalities, Chapter 7 (Max Wein, Mr Hewlett and a Rainy Sunday Afternoon)].
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thanks RoGeorge
http://www.introni.it/pdf/Williams%2007%20-%20Book%20Chapters.pdf
also found it here - in the book Gyro pointed to
http://s1.nonlinear.ir/epublish/book/Analog_Circuit_Design_Art_Science_and_Personalities_0750696400.pdf
fascinating article, Jim Williams is always insightful. I think this is the first thing i've read of his that was not an application note. i really like how he walks you though the process of what he did and why.
innkeeper:
--- Quote from: Yansi on January 09, 2020, 09:33:28 pm ---Use a decent computer soundcurt plus a suitable software. Easy, done.
You can then easily change test frequency, and even do test like a two tone (IMD).
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can you give me an example setup with its thd+n figures?
Gyro:
--- Quote from: innkeeper on January 10, 2020, 10:15:59 pm ---...
fascinating article, Jim Williams is always insightful. I think this is the first thing i've read of his that was not an application note. i really like how he walks you though the process of what he did and why.
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There's another, equally good book, also edited by Jim Williams, in that EDN series called 'The Art and Science of Analog Circuit Design'. I have paperback copies of them both and find them nice to settle down with on the occasional rainy afternoon.
MasterT:
Wien-SG_Elektor-1994-12.pdf (131.28 kB - downloaded 330 times.)
I've build one recently, to test my 18-bits differential AD7984 board. I changed OPA to LM4562, and use 7370-18V-0.04mA lamp. Circuits does need "manual" tuning to get the lowest THD, but accounting simplicity it's not an obstacle. Results thd-2 ~0.0004% (-110dB) and thd-3 ~0.0002 (-114dB) at 4kHz. Not sure about 100kHz, ADC itself has thd-3 ~0.002% at this frequency.
My attempts to replace lamp with CdS photocell or thermistor MF52 in the amplitude control loop were really disappointing. Despite what they say in app note, CdS is highly non-linear material, and may works only in the <100 mV range, making control loop very limited in the dynamic range sense.
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