Does anyone have any experience with this kit? I built it as a cheap function generator but I'd like to clean up the harmonics in the output. Am I hoping for two much from this cheap kit?
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Are they consistent up and down the band? or they emerge as you climb or descend or something?
It is a bare bones very basic little unit. Are you running it off a super clean supply? The filter on the board looks minimal, possible coupling. I'd prefer it were in a metal box for shielding, but I doubt that it the issue.
Harmonics of 1kHz ought to be at 2k, 4k, 8k, etc. Your overtones are at 3k, 5k, 7k etc. So I don't know if that is a limitation of the chip, but then if your scope is digital, is it possible they are artifacts? Can you hear them? if you change the frequency, do you have them at similar relationship to the fundamental?
It is a bare bones very basic little unit. Are you running it off a super clean supply? The filter on the board looks minimal, possible coupling. I'd prefer it were in a metal box for shielding, but I doubt that it the issue.
Harmonics of 1kHz ought to be at 2k, 4k, 8k, etc. Your overtones are at 3k, 5k, 7k etc. So I don't know if that is a limitation of the chip, but then if your scope is digital, is it possible they are artifacts? Can you hear them? if you change the frequency, do you have them at similar relationship to the fundamental?
The supply is SMPS, I doubt its super clean. My spectrum analyzer is digital. I'm running it with a decent quality Behringer UCA-202 USB sound card. I figured the circuit was too simple to give good quality, even though I was crossing my fingers.
I don't want to spend a ton of money for a function generator as I don't use it a lot. I'm looking to replace my ancient Wavetek 188 which has a bunch of garbage in its output. I guess I could rebuild the Wavetek but not sure if it's worth it.
I'm trying to adjust my Technics SH-9010 equalizer so that I can sell it. To that end, I need a clean and accurate sine wave. I might resort to using my spectrum analyzer software to generate the sine waves.
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I don't want to spend a ton of money for a function generator as I don't use it a lot. I'm looking to replace my ancient Wavetek 188 which has a bunch of garbage in its output. I guess I could rebuild the Wavetek but not sure if it's worth it.
I'm trying to adjust my Technics SH-9010 equalizer so that I can sell it. To that end, I need a clean and accurate sine wave. I might resort to using my spectrum analyzer software to generate the sine waves.
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Is something like this better quality: https://www.ebay.com/itm/191787360703
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Looks like a better value, but it's probably a similar chip with similar distortion.
You can buy an old HP 200 series audio oscillator for far superior results. Not expensive, and you could sell it for what you paid when you tire of it. That tends to be the difference between a "function generator" and an "oscillator." Performance.
Analog function generators are designed for flexibility in waveform not for
purity in the sine output. What are your goals? Why not just use the
audio out from an old laptop? You can get a free digital function generator
program and it will provide reasonably low distortion.
fg_lite provides sine output, I've not measured the purity, perhaps give it
a try. It is not a true function generator since it doesn't provide square and
triangle output:
http://www.marchandelec.com/programs.html
purity in the sine output. What are your goals? Why not just use the
audio out from an old laptop? You can get a free digital function generator
program and it will provide reasonably low distortion.
fg_lite provides sine output, I've not measured the purity, perhaps give it
a try. It is not a true function generator since it doesn't provide square and
triangle output:
http://www.marchandelec.com/programs.html
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Pin 13 is "THD adjust". Look at the data sheet and add a pot between pins 13 and 14. Tweak it til the THD plots look better.
I'm going to use my raspberry pi and outboard DAC to reproduce sine waves I've downloaded from wavfiles.com To amplify the DAC output I'm building a TPA6120 headphone amp kit. Probably a "trip round dick's barn" approach but I already have the raspberry pi coupled to my HRT DAC as a high definition portable media player. The headphone amp will do double duty as a portable amp for small speakers.
Waveform purity and low thd are my key requirements.
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The Waveteks use a shaping circuit so aren't super low THD. Still, I find them most useful at the bench. They're prone to bad e-caps at this age, and I've had some cheap IC socket problems, plus cracked solder joints on front panel controls. Fix all that and they're good for another couple decades. OTOH, if you need low THD, that ain't it; there have been many discussions on both DIY and commercial low THD generators here.
[emoji106]
I'm sure the pun was unintentional but my tired, geek mind found it hilarious.
a frequency generator ... "good for another couple decades"
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Won a Leader LAG-120B for $40. Looking forward to testing it out.
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