Hi all , first post here I'd like to make a fft and harmonics analysis on a synthesizer's sine wave vco, given that the wave output is not pure and features some extra harmonics: I want to detect them correctly and straight on the output of the vco because I don't want to get artifacts: is there a way to sample a waveform straightly from the circuit and make a FFT of it? Thx for any reply Max
"Max Fazio" wrote in news:445f9cb4$0$14777$ snipped-for-privacy@reader4.news.tin.it:
Sound Forge. :)
That will let you look at the time domain too, which might be just as revealing.
Tapping the VCO will be easy enough, but you'll need to identify the IC and the pin it puts out the signal on, and then match the level to get the best use of the 16 bit recording in Sound Forge. If you have a 24 bit 96 KHz input, use it if you want to test frequencies above about 5 KHz.
OK, I got SF ;) But the problem is: if I have to sample the wave from the pin of the VCO do I have to use probes like for Oscilloscopes? What I know is that I should grab the waveform straightly from a Yamaha iG00150 which is actually a LFO whose highest frequency is 222Hz: the sine is actually a waveshaped triangle, therefore there are some harmonics going on the waveform What is the tool I can use to grab the waveform? a microphone?a probe?? Let me know! M
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best
"Max Fazio" wrote in news:445fb9a8$0$18283$ snipped-for-privacy@reader1.news.tin.it:
Yes, use a probe the same way as for a scope. One advantage to Sound Forge is you just start it recording, then you don't have to watch anything but where you put the probe tips. Connect the probes to the tip and sleeve connections on the jack to a sound card input. take care with the VCO output though, check with a voltmeter or scope first. Ideally, set to sine wave at 50 or 60 Hz so you can measure the AC output voltage. Some VCO's will put out 15 volts or so, and you'll need to attenuate that witha variable resistor to match it to the sound card input. Just start low, crank it up while watching the record level meter, till just short of clipping.
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