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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Mixing CMOS outputs--Some problems I don't understand
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Dr. K



Joined: Jan 15, 2020
Posts: 27
Location: wisconsin

PostPosted: Mon May 25, 2020 4:36 am    Post subject: Mixing CMOS outputs--Some problems I don't understand Reply with quote  Mark this post and the followings unread

Hello Folks,
Looking for some advice. I'm tinkering with some logic chips, and am running in to a problem. I have configured a 40106 as a series of basic square wave oscillators. I'm running 3 of them into a 4070 XOR chip. 2 of the 40106 outputs go to on of the XORs. The output of that, and another 40106 oscillator, goes to the inputs of another XOR. That seems to work--it's a nice, weird, noise free, loud sound.

Then I've taken 2 more of the 40106 oscs, and pumped them into a 4093 NAND gate. That output works too.

Here's the problem I don't get. I want to mix the 4070 and the 4093 outputs to one jack. I've tried coupling them with diodes, I've tried coupling them with resistors. I've tried diodes and resistors in series. But I get a very muted sound. The output is a fraction of either of the outputs alone.

I'm not sure what's going on? As I said--uncoupled, the 2 signals are good and healthy and clean. Tied together, the output is really anemic.

Any thoughs on why that should be happening? How to fix it?
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Steveg



Joined: Apr 23, 2015
Posts: 182
Location: Perth, Australia

PostPosted: Mon May 25, 2020 5:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Dr K, What value resistors? What is it going into?
I cant think of any issues unless you have something causing problems in the output stages of the chips. Maybe something in the circuit is acting as a voltage divider. That's why knowing what you are connecting to would help.
Steve
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dk



Joined: Feb 12, 2019
Posts: 115
Location: Europe

PostPosted: Mon May 25, 2020 9:01 am    Post subject: Reply with quote  Mark this post and the followings unread

When you used diodes, did you have a resistor tied to ground/+V after them? It's my understanding that with digital signals, diode mixing is essentially making an AND or OR gate (depending on which way they're facing), so there should be a reference after them (see diode AND and diode OR here: http://electro-music.com/forum/topic-70288.html )
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