Electronics > Projects, Designs, and Technical Stuff
World-class sine wave generator for cheap?
basinstreetdesign:
Back when building a tube stereo amp I needed a fairly good sine signal to test distortion but I didn't have such a thing. So building one went on my long-term ToDo list. I've heard about oscillators with THD at -120dB and I thought it would be cool to have that. But how? They cost mucho$ (Audio Precisions' System One). Building a digital source needed an elaborate DDS system, parts I didn't have and probably SW so didn't attract me. So I thought maybe it could be done with a good 'ol Wein bridge oscillator.
I posted a question about this project some time ago. Thanks for all who responded to it but I ended up choosing a more low-class solution to my problem than what I had originally hoped.
Here is a picture story documenting progress...
https://imgur.com/a/Buj8WfD
It's not finished, but,
what do you think?
Conrad Hoffman:
Nice! The bulb solution works well but usually limits the THD at low frequencies. I assume you've read all the historical stuff on the HP200A that Bill Hewlett did his thesis on. I've used the oscillator in the Bob Cordell spectrum analyzer article as inspiration. http://www.cordellaudio.com/papers/build_a_thd_analyzer.shtml It's very inexpensive to build and does about 0.0002% if well tweaked. There are some threads about ultra low THD oscillators at the DIYaudio forum too.
Vovk_Z:
The cheapeast, simplest and the best one is Victor's ultra low distortion oscillator.
duak:
Interesting design and build. Thx for sharing!
If you're having trouble with the EM field from the transformer, a copper strap around the winding and core can help. I can't find an image of exactly how it's done, but the attached image should give you a good idea. It doesn't go through the core otherwise it would form a shorted turn. I can't remember if its supposed to be grounded or not. I expect it should be. It is a complete loop with the ends electrically connected together.
mcovington:
Wien, not Wein.
Pronounced 'veen.'
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