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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
mixing oscillators with diodes - help
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piupiupiu



Joined: May 04, 2020
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PostPosted: Fri Jan 15, 2021 10:32 am    Post subject: mixing oscillators with diodes - help
Subject description: understanding load resistor
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Hello !

Im a newbie learning cmos circuits, I have been reading some information online and at Nicolas Collins book Handmade Electronic Music.
Im experimenting now with mixing techniques of oscillators and trying to understand what is happening in the circuits.
At the book of nicolas, when using diodes at the mixing bus, he says you should add a resistor of around 10k to ground. Can someone help me understand it? Why its used? You should always use a resistor there? I have tried to search about it, but couldnt find information about this, I have seen some people not applying it to their circuits when using diodes for mixing with 40106 and 4093 chips, but maybe because they have a general volume potentiometer on the output?

thank you! Smile


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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Fri Jan 15, 2021 1:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

welcome party!

It does depend on what you connect it to but one thing to think about is what happens to the output of the mixer
if the outputs of all the oscillators are low. Also if for example you connect it to an input that has a capacitor in series,
which might happen with an audio input, then it will just charge that capacitor which will result in the sound fading out.
And for current to flow though a diode the cathode needs to be at a lower voltage then the anode which is often done
with a resistor to ground.

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piedwagtail



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PostPosted: Fri Jan 15, 2021 4:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

V=IR if you don't have a resistance there's no circuit - voltage measurable or current seen.
10k is a standard load to give our 40106 output transistors an easy time. If it was 10 ohms they'd be trying to push huge currents to give you a 'high'.
You know what happens when things work too hard...heat.
Frequency also comes into this, some loads are not equal across the frequency spectrum.
Your research topic is Impedance.

R
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piupiupiu



Joined: May 04, 2020
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PostPosted: Fri Jan 15, 2021 4:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
welcome party!

It does depend on what you connect it to but one thing to think about is what happens to the output of the mixer
if the outputs of all the oscillators are low. Also if for example you connect it to an input that has a capacitor in series,
which might happen with an audio input, then it will just charge that capacitor which will result in the sound fading out.
And for current to flow though a diode the cathode needs to be at a lower voltage then the anode which is often done
with a resistor to ground.



thank you PHOBoS !! Very Happy I'm starting to understand it better! I was just going to connect two oscillators from a 4093 mixed with diodes directly to a jack output with an output attenuation, so i should keep the 10k. I have to study more about diodes too.


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piupiupiu



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PostPosted: Fri Jan 15, 2021 4:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

piedwagtail wrote:
V=IR if you don't have a resistance there's no circuit - voltage measurable or current seen.
10k is a standard load to give our 40106 output transistors an easy time. If it was 10 ohms they'd be trying to push huge currents to give you a 'high'.
You know what happens when things work too hard...heat.
Frequency also comes into this, some loads are not equal across the frequency spectrum.
Your research topic is Impedance.

R


Thank you so much for your explanation and advice piedwagtail! I definitely have to study about impedance!! I will search and read more about it!
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