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Question: Cheap pure sine wave genertor 1khz?

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RoGeorge:

--- Quote from: Gyro on January 10, 2020, 10:49:03 am ---[Analog Circuit Design - Art, Science and Personalities, Chapter 7 (Max Wein, Mr Hewlett and a Rainy Sunday Afternoon)].
--- End quote ---

That one is a good example, too, available online:
http://www.introni.it/pdf/Williams%2007%20-%20Book%20Chapters.pdf

Vovk_Z:
The best 1kHz oscillator I know (with best price/thd ratio) is Victor's ultra low distortion oscillator. You can find him at diyaudio.com, he sells sometimes readymade modules via ebay. It is Wien bridge type, and it is cheap. Here it is.
But the answer depends on what TS mean at "pure sine wave"? How much pure?
DDS signal gereators need something like Arduino to program them.

Grandchuck:
Low distortion is easy but very low distortion is not.  The best one (circuit) here is showing 0.0016% but is probably better since the old HP analyzer is not great with very low distortion measurements.  The circuit is described here:  http://www.redcircuits.com/Page82.htm

The problem with this one is that the dual potentiometer should have very low tracking error and such a part is hard to find.

Having tried several different kinds of very low distortion circuits, my conclusion is they are all 'fiddley".

innkeeper:

--- 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

--- End quote ---
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.

Gyro:

--- Quote from: Grandchuck on January 10, 2020, 09:43:43 pm ---Low distortion is easy but very low distortion is not.  The best one (circuit) here is showing 0.0016% but is probably better since the old HP analyzer is not great with very low distortion measurements.  The circuit is described here:  http://www.redcircuits.com/Page82.htm

The problem with this one is that the dual potentiometer should have very low tracking error and such a part is hard to find.

Having tried several different kinds of very low distortion circuits, my conclusion is they are all 'fiddley".

--- End quote ---

This is the first time I've seen independent verification of (the performance of) that circuit, thanks. [Edit: I was planning to build it a few years back but a Topward TAG-4005 came up really cheap on ebay that manages quite a bit better than its specified 0.005%.]

Construction and trimming would be a considerably easier for one (or a few) spot frequencies of course.

Fiddley is the word, that is demonstrated very well in that Jim Williams chapter.

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