Are you trying to make a variable pitch whistle? Some kind of sound effect?
What is your context?

Weren't you able to deduce that this is a 555 noise maker circuit that he is using to make a DIY synthesizer. Once it's done, he'll learn to play Baba O'Riley and get his hair bleached and permed before he goes out touring. The chicks will dig him 'cuz he's groovy. They will call him Pete.

 

I could believe the synthesizer angle if he was working with sine waves. Any square wave or product of square waves is going to sound harsh: to put a word on it. If that's the goal, then rock on dude, but you'll find very little in the way of theory to describe non-linear combinations of square waves.

Turns out there are square wave synthesizers on YouTube that sound.....well harsh. So I guesss there might be a following for harsh. If I was going to pick a logic function for square waves it would be exclusive-OR, and I would capacitively couple the output to the audio amplifier.

 

When it comes to signals Bob, AND is not the same thing as multiply. Anytime either signal is at 0 Volts you have no output. Riddle me this Bob, how would you demodulate the AND of two square waves. Missing some information to do that are we?

It most certainly is. 0 x 0 = 0, 0 x 1 = 0, 1 x 0 = 0, 1 x 1 = 1

Consider a 1Hz square wave modulaing a 1000Hz square wave. You get 1/2 second of 0,followed by 1/2 second of 1000Hz. I can certainly demodulate that.

I think you are taking too narrow a view of modulation.

Bob

 

AO transmission is un-modulated. As the 1000 hz would be.
Unless they have changed it.

 

I will breadboard two of these circuits and take your advice on this thread. I am also going to make an active mixer.

 

Disconnect the connections at X2-1 and X2-2. Energize the board and see what the signal at TP looks like with your scope. That's the gate of Q2.
My question is, why do you want to mix the two signals so soon? Do you need two separate channels (with different frequencies) in the future?
Are you trying to make a variable pitch whistle? Some kind of sound effect?
What is your context?

If I want to send two of these squarewaves to one speaker I want to have the option of no modulation. But I will test the TP and see.

 

Hello,

When you want both signals on one out put try the following:



When one of the signals is high, the output will be low.
See with your scope how it looks like.

Bertus

 

Hello,

When you want both signals on one out put try the following:

View attachment 109073

When one of the signals is high, the output will be low.
See with your scope how it looks like.

Bertus

That assumes the MOSFET will not turn on at 4.5V (if one is on and one is off and you are looking for an AND effect).

Would it be better to make an AND with two MOSFETs in series on the output. One NoiseMaker circuit diving a separate MOSFET gate - a more traditional AND circuit?

 

Hello,

When you want both signals on one out put try the following:

View attachment 109073

When one of the signals is high, the output will be low.
See with your scope how it looks like.

Bertus

Yes I've done this and one oscillator cuts the other one out. I think it is the same as before, it's like a voltage controlled amplifier. Like a gate opening and closing. I think it's called an All Gate. If I have one at high frequency and the other low I get a repetitive bleep, as the low frequency squarewave is opening and closing letting the high frequency through, like a reversing vehicle alarm sound. Bleep bleep bleep.

 

Hello,

Did you already have a look at the weird sound generator on Music from Outer Space?
http://www.musicfromouterspace.com/analogsynth_new/WSG2010/wsg_page1.html
http://www.musicfromouterspace.com/analogsynth_new/WSG2010/wsg_page2.html
http://www.musicfromouterspace.com/analogsynth_new/WSG2010/wsg_page3.html
http://www.musicfromouterspace.com/analogsynth_new/WSG2010/wsg_page10.html

That can create a lot of sounds as shown on page 1 and 10

Bertus

 

Hello,

Did you already have a look at the weird sound generator on Music from Outer Space?
http://www.musicfromouterspace.com/analogsynth_new/WSG2010/wsg_page1.html
http://www.musicfromouterspace.com/analogsynth_new/WSG2010/wsg_page2.html
http://www.musicfromouterspace.com/analogsynth_new/WSG2010/wsg_page3.html
http://www.musicfromouterspace.com/analogsynth_new/WSG2010/wsg_page10.html

That can create a lot of sounds as shown on page 1 and 10
Yes I have a MFOS Sound Lab, it is fairly similar, very good! Im a big fan of MFOS as I have built 2 VCA's and they work very nicely!!
Bertus

 

Im going to build this mixer, I have added 4 outputs instead of one, it is a Ray Wilson active mixer

 

That assumes the MOSFET will not turn on at 4.5V (if one is on and one is off and you are looking for an AND effect).

Would it be better to make an AND with two MOSFETs in series on the output. One NoiseMaker circuit diving a separate MOSFET gate - a more traditional AND circuit?

This sounds interesting, do you mean like this??? Or


Like this?

 

This sounds interesting, do you mean like this??? Or
View attachment 109094

Like this?
View attachment 109095

Yes. That's the idea.

 

I could believe the synthesizer angle if he was working with sine waves. Any square wave or product of square waves is going to sound harsh: to put a word on it. If that's the goal, then rock on dude, but you'll find very little in the way of theory to describe non-linear combinations of square waves.

Turns out there are square wave synthesizers on YouTube that sound.....well harsh. So I guesss there might be a following for harsh. If I was going to pick a logic function for square waves it would be exclusive-OR, and I would capacitively couple the output to the audio amplifier.

Square and sawtooth have been staple analog synth waveforms for 50 years or more. Yes they sound harsh on their own, but that's why synths have filters.

 

A fundamental problem with the original circuit in whatever your application is, is Q2. As mentioned, Q2 is normally used to switch a load to ground. This is a very asymmetrical output impedance and waveform, even if you replace the diode with a pull up resistor. Taking the post #47 schematic one step farther, eliminate Q2 from both circuits and take the output from the junction of the two R3's. This will be a resistive sum of the two square waves, each driven by a symmetrical output stage, so at various points in the waveform the voltage will be almost 0 V, around 4 V, or around 8 V. This is the normal result of a resistive mix of two square waves of different frequencies. A 4013 can't make more than 4 mA, and the output shapes will be better at light loads. With a 9 V battery, the two R3's should be 10K each or more. Add one coupling capacitor to the summed output and you have an audio signal other gear can deal with. Note that the equivalent output impedance will be 5 K, a bit higher than most signal sources.

Without getting into signal amplitude and output drive capability, the result should be the same as the output from an active mixer. Why? Because in both active mixer schematics (posts 23 and 52), at some point all input signals are resistively summed together.

ak

 

Square and sawtooth have been staple analog synth waveforms for 50 years or more. Yes they sound harsh on their own, but that's why synths have filters.[/

A fundamental problem with the original circuit in whatever your application is, is Q2. As mentioned, Q2 is normally used to switch a load to ground. This is a very asymmetrical output impedance and waveform, even if you replace the diode with a pull up resistor. Taking the post #47 schematic one step farther, eliminate Q2 from both circuits and take the output from the junction of the two R3's. This will be a resistive sum of the two square waves, each driven by a symmetrical output stage, so at various points in the waveform the voltage will be almost 0 V, around 4 V, or around 8 V. This is the normal result of a resistive mix of two square waves of different frequencies. A 4013 can't make more than 4 mA, and the output shapes will be better at light loads. With a 9 V battery, the two R3's should be 10K each or more. Add one coupling capacitor to the summed output and you have an audio signal other gear can deal with. Note that the equivalent output impedance will be 5 K, a bit higher than most signal sources.

Without getting into signal amplitude and output drive capability, the result should be the same as the output from an active mixer. Why? Because in both active mixer schematics (posts 23 and 52), at some point all input signals are resistively summed together.

ak

Sounds like a great solution, I'll try this tomorrow thanks!!

 

555 Absolute max. is 16V or 18V depending on provider which the datasheet does not specify
4013 Absolute max. is 15V to 20V depending on provider which the datasheet does not specify
i recommend upper lim 14V-15V
the value of C3 sets the limits for load current or requires a supply meeting your output requirements (in which case the X1-1 should be directly connected to X2-2 e.g. replace D2 with ∅1mm copper jumper)
. . .

 

Is the task "just" to mix the two square wave signals as one would mix two analog signals?

If so, the obvious solution is to take the two '4013 outputs and mix them through two sufficiently large resistors to one single signal.

 

Your latest schematic gives you an AND between the two outputs, and definitely modulate one with the other.

If you want the sum of the two signals, as someone else said, simply connect the outputs through each through a resistor to the next stage input. The size of the resistors will depend on what you are trying to drive. If it is a speaker, you would not want to do it the way, you need an amplifier in between. If it is a line level input, a resistor of about 1K would work fine.

Bob