"when i put the outputs together", What outputs are you putting together? I see one output. You're just switching to ground.

Where are two square waves generated and where are they added?

Edit: you mean two separate boards?

 

Pardon me, If that's it, you have two boards, the the difference is phase. Which is different than frequency.

It should be a resultant, not a modulation.

 

Pardon me, If that's it, you have two boards, the the difference is phase. Which is different than frequency.

It should be a resultant, not a modulation.

Yes it is two separate boards, as you can see there in the white box and then going down to the aluminium modules. on the right there is a multiple mixer, this is passive. But I found when I use the Ampmix (black mixer module) it has a all out at the bottom and this works! you can see the schematic below.

 

Hello,

Do you use an attenuator at the output of the oscillator?
It looks like the mixer circuit amplifies the input about 2 times.
When you want to stay within line level, you should reduce the signal to max 1 Vpp.
https://en.wikipedia.org/wiki/Line_level

Bertus

 

The squarewave output is +/- 5v so it works with my synth modules. Yes the module does amplify about 2 times but I keep it in the middle of the pot so the output of the mixer remains +/- 5v.

 

I believe it is something to do with the diode D1 on the schematic. I have seen on other circuits that produce modulation have diodes. This is an educated guess but I will try to get another output from GND and TP.

 

I cannot make any sense out of how you have connected things. You need to give us a schematic if you want any better help.

Bob

 

Looks like somebody has a great deal of stuff and no clue what he is doing with it. I don't see modulation at all. The clue is that actual modulation requires a non-linear process like multiplication. I can't imaging what square waves through a mixer would even look like. Maybe sums and differences of the fundamental and all possible harmonics in the Fourier Expansion for each square wave. It's all a bunch of DRUMPF!

 

Looks like somebody has a great deal of stuff and no clue what he is doing with it. I don't see modulation at all. The clue is that actual modulation requires a non-linear process like multiplication. I can't imaging what square waves through a mixer would even look like. Maybe sums and differences of the fundamental and all possible harmonics in the Fourier Expansion for each square wave. It's all a bunch of DRUMPF!

Ok Papabravo, I made this all myself this is a DIY project, I know exactly what is going on except for this problem . I'll send a full schematic tonight.

 

Your post #26 schematic shows a circuit apparently intended originally to drive a relay, motor or other inductive load: hence the presence of D1 as a spike-suppressor. Unless you will be driving a loudspeaker directly from the FET (not recommended) I suggest you replace D1 with a resistor in the 1kΩ to 3kΩ range and take your output from the FET drain (point X2-1) via a 470nF capacitor (assuming your mixer has an input impedance > ~20kΩ).

 

Your post #26 schematic shows a circuit apparently intended originally to drive a relay, motor or other inductive load: hence the presence of D1 as a spike-suppressor. Unless you will be driving a loudspeaker directly from the FET (not recommended) I suggest you replace D1 with a resistor in the 1kΩ to 3kΩ range and take your output from the FET drain (point X2-1) via a 470nF capacitor (assuming your mixer has an input impedance > ~20kΩ).

Yes it is intended to drive a small speaker, that's great advice, thanks!!

 

Yes it is intended to drive a small speaker

That would put a lot of DC current through the speaker, resulting in gross distortion.

 

Ok Papabravo, I made this all myself this is a DIY project, I know exactly what is going on except for this problemView attachment 108994 . I'll send a full schematic tonight.

I don't doubt that you are a skilled technician and fabricator. When it comes to theory, design, and understanding maybe not so much. That's not a bad thing since you can certainly improve.

 

Looks like somebody has a great deal of stuff and no clue what he is doing with it. I don't see modulation at all. The clue is that actual modulation requires a non-linear process like multiplication. I can't imaging what square waves through a mixer would even look like. Maybe sums and differences of the fundamental and all possible harmonics in the Fourier Expansion for each square wave. It's all a bunch of DRUMPF!

If he connected it the way I suspect: one wire of the speaker to both MOSFET drains, and the other to V+, the output would be the AND of the two signals, which is a multiplying operation and would, I think, result in modulation.

Bob

 

Here is the full schematic, as you can see the when the two outputs are connected there is modulation. There are two oscilloscope images, the first is two square separate waves unmodulated, the second is the same two square waves connected (as in the schematic)
Modulated, this is unwanted.




unmodulated


modulated

 

If he connected it the way I suspect: one wire of the speaker to both MOSFET drains, and the other to V+, the output would be the AND of the two signals, which is a multiplying operation and would, I think, result in modulation.

Bob

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?

 

Tony, those two boards are not square wave generators. Neither one generates a square wave.
Those are called low side switches. They switch power to a load, on the low side, (the return path, sorta speak), of the circuit.

May I see a schematic or photo of your "passive load"?

 

Tony, those two boards are not square wave generators. Neither one generates a square wave.
Those are called low side switches. They switch power to a load, on the low side, (the return path, sorta speak), of the circuit.

May I see a schematic or photo of your "passive load"?

Low side switches, that's interesting I'll have to look into this! Here is the passive mixer

 

What signal do you want out of this mess and where are your probes placed on your scope image?

Also, why just use three pots when we have the technology to make summing amplifiers and avoid this mess.

 

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?