a quest to build a sine+cos LFO

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Post by guest » Thu Mar 28, 2019 12:15 pm

if you increase the oscillation frequency, do the dots go away? im guessing it has something to do with the oscillation frequency being a multiple of the sampling frequency, so youre getting periodic points. i dont know that scope very well, but sometimes there is a "vectors" setting in the display menu for showing just points or connecting the dots.
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Synthiq
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Post by Synthiq » Thu Mar 28, 2019 4:04 pm

charonme wrote: btw I don't know why the plot is a discontinuous patch of blotches instead of a nice thin line. I tried different scope settings with no luck
In the second plot from the scope the menu says the display type is set to dots. Try to change the interpolation method to sin(x)/x to see if it makes a difference.

[Edit] I also notice that the sample rate is 100Msps or 250Msps in your plots. If you don't have a very deep scope memory, each sweep may only catch a small portion of a period of your signal and may be displayed as a dot per sweep. In this case, try to lower the sample rate to cover more than one period of the signal per sweep.

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charonme
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Post by charonme » Sat Mar 30, 2019 4:45 am

well I just have a crappy scope - no wonder, it was the cheapest :lol:
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Heptaphasis - DIY 3HP 7-phase quadrature sine LFO

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charonme
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Post by charonme » Tue Apr 02, 2019 4:44 am

finally I finished the schematic

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Heptaphasis - DIY 3HP 7-phase quadrature sine LFO

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Post by guest » Tue Apr 02, 2019 12:27 pm

awesome. looks good.
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charonme
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Post by charonme » Sat Apr 06, 2019 7:35 am

dedicated thread for the result: viewtopic.php?t=215780
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Heptaphasis - DIY 3HP 7-phase quadrature sine LFO

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gabba@gabi
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Post by gabba@gabi » Fri Apr 12, 2019 12:29 pm

with best regards,
but without waveshaper´s

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nigel
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Post by nigel » Sat Apr 13, 2019 4:43 am

You don't like 315 degrees?

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charonme
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Post by charonme » Sat Apr 13, 2019 4:53 am

nigel wrote:You don't like 315 degrees?
I only have room for 7 :(
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and the board would probably have to be bigger too to fit another opamp
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Heptaphasis - DIY 3HP 7-phase quadrature sine LFO

frijitz
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ChaQuO

Post by frijitz » Thu May 23, 2019 10:21 pm

charonme wrote:thanks
I might have to downgrade my expectations, so perhaps a 3 or 4 op-amp circuit would be OK, but I still want a sine and a cosine LFO output controlled with one pot :)
The ChaQuO module was developed over 10 yrs ago, both in DIY and commercial versions. It includes a 3 opamp quadrature osc with a dual pot for tuning.
http://ijfritz.byethost4.com/Chaos/ch_cir8_chaquo.htm
(See the doclink for the pdf doc)

Looks like someone posted a somewhat similar schematic above; this is my original version. It uses a x-x^3 nonlinearity rather than clipping.

Ian

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