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Question: Cheap pure sine wave genertor 1khz?
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innkeeper:
I'm looking to generate a low thd sine wave to do some THD testing with a DSA.
the internal generator on my DSA is not clean enough for any critical THD testing.

id like it to be 1khz, and will be used for line level input to amplifiers. so 2.1v out max or less. probably down to like 1.2v in that range.

happy building up a circuit or buy one pre built on the cheap.  any ideas?

i could swear i've seen such projects in the past but came up empty in my recent searches.
Yansi:
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).

RoGeorge:
If you want to build a generator, this type is hard to beat in performance:
https://www.eevblog.com/forum/projects/low-distortion-audio-oscillator-stabilized-via-trigonometric-identity/

There are some linear application notes, too, from the '70s or the '80s, explaining this topology.  Can't find them right now.
David Hess:
The simplest single operational amplifier Wien Bridge can achieve 0.0025%.  Doing better requires buffering the output and adding common mode suppression which will get you to 0.0003%.  See Linear Technology application note 43.

Doing better than that gets complicated but see Linear Technology application note 67 for an example of what is required to test a modern audio ADC to 18 bits or better.
Kleinstein:
A good sound card is an easy solution.

For a DIY solution the best bet is likely a Wien bridge oscillator of some kind with really low THD amplifiers. There a quite a few old plans and application notes.  With fixed frequency, there is no real need for the fancy amplitude regulation using instant amplitude measurement, as much less action from the amplitude stabilization is needed. There is an LT appl. Note to get super low THD by combing 3 OPs for each inverting amplifier.
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