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<div class="moz-cite-prefix">HI A.M.,<br>
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<div class="moz-cite-prefix">On 20.02.2023 18:10, A.M. Barrio via
Synth-diy wrote:<br>
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<li>To David Huss, René Schmitz, Lukas Hazen-Bushbaker:
thanks a lot for your thorough explanation on why this is
happening. At least I can say I now understand what's
going on. David's bucket analogy in particular made it
super easy for me to grasp the idea. In the process,
though, you also gave me a feeling that these matters
might be a little too complicated for me to manage haha!
I'm no engineer nor do I have as much knowledge on
electronics as I'd like to... I actually do have some, I
work as a technician repairing stuff, but the reasons
behind my problem and the solutions to it caught me off
guard. I was never taught too much on noise issues back
when I was studying, I suppose it is explored more deeply
in actual EE degrees. As a result I've never been aware of
it: there are no 100uF caps anywhere on the entire synth
case, my bus board is the crappiest, most DIY thing you
can think of and my way-to-go has always been <i>slap in
those 100nF caps between rails and go test it!</i> So
much for me to learn on this topic.</li>
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<p>The big caps 100u belong in one place, in your PSU. <br>
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<li>To René Schmitz, Roman Sowa: I must note that the
schematic I attached on the first email is not the LFO,
but the clock, that's my bad again. That's why there's
only one LED. However I just noticed that I didn't rectify
the signal before plugging it to U1C, so the negative
cycles are indeed going nowhere. I will change that in the
clock circuit. On the LFO circuit I do have two LEDs per
wave, one for positive cycles and one for negative cycles.
Took notes about high efficiency LEDs as well, right now
I'm using a plain common red LED on the clock and six
green (!) LEDs on the LFO, since it has three wave types.
I'm still concerned about the LEDs however... a total of 7
LEDs might take around 140mA, would that be correct? Even
if I were to correctly bypass all my circuits and properly
isolate everything, would the LEDs still suppose an issue
in terms of sag/wiggle for a PSU that can supply much
more? (all of the PSUs I tried with can supply around 1A
max).<br>
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<p>If you rectify the clock the LED will be always on. <br>
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<p>Btw, you can also run regular LEDs at reduced current. 2mA is
usually sufficient to see them in indirect daylight. No need to
drive them to 30mA. <br>
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<li>To Mike Beauchamp, Chris McDowell, Roman Sowa: The VCO
design comes from Moritz Klein's one. I'm attaching a
schematic of the exact circuit I'm implementing. After
reading all the responses it is quite obvious to me that
it is VERY prone to changes in output frequency: the CV
pots are tied directly to the rails, as well as the
CD40106 IC in charge of generating the oscillation. Roman,
I am taking absolutely no offense from your comment: it is
indeed a bad design. I am not willing to improve <i>this</i>
particular VCO design as it was just a test and a bad
example of me being too excited to have my first panel
mounted on my case. Please ignore the wasteful use of the
40106 and the crappy expo converter, much more care will
be put into the next VCO I put together. About this: <i>
If you need help deciding which ones those are, post the
VCO schematics.</i> Would you mind pointing them out? I
mentioned a couple spots above, but I'd like to make sure
I cover them all. That being said, I'd love to hear about
the reference voltages. Chris, thanks for the IC examples,
I'll check them out. Besides, I have some spare 7805
regulators at home. Although they are quite big, would
they do the job for testing before I go ahead and grab
some of the examples you mentioned?
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<p>I guess I'm partly to blame, or could take offense, but won't. :)
Moritz Klein "borrowed" the expo and summing stage of my VCO4069.
And this had the same problems. <br>
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<p>But hey, I did that over 20 years ago. It really only is a
problem when you can't know what else you share the power rails
with. (you'll see this a lot with older synth designs)<br>
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<p>You'd be right with powering the 40106 from a well regulated
voltage and the pots and the expo reference current would need to
be made independent of the supply rail. <br>
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<p>Best,</p>
<p> René<br>
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