Adding additional oscillators to simple 8 step sequencer

Thread Starter

bignobody

Joined Jan 21, 2020
50
Hi there!

I made a breadboard version of this simple 8 step sequencer on the weekend : https://hackaday.com/2015/02/23/logic-noise-the-switching-sequencer/
It's a lot of fun to play with.

I want to make a more permanent version, and I'd like to scale it up to have the sequencer drive 4 additional oscillators.

In the original schematic there are two signals that go to the oscillator: the common signal from pin 3 of the CD4051 which goes to the oscillator input pin, and the CD4051 switching signal (through one of 8 pots) that connects to the oscillator output pin.

If I want this to drive 5 oscillators instead of just one, I think I need to send both of these signals to 5 buffer inputs and send the buffered outputs to each oscillator.

With a bit more detail:

Common signal from pin 3 of the CD4051 to 5 inputs of a CD4069, 5 outputs of the CD4069 to 5 inputs of a CD40106.
Switching signal from CD4051 (through pots) to 5 inputs of another CD4069, 5 outputs of the CD4069 to 5 outputs of a CD40106.

Can anyone confirm if I've got the right idea here?
 

ronsimpson

Joined Oct 7, 2019
439
I posted the schematic because I can't see the schematic and read your text at the same time.
Do you want 5 Outputs? Each output at a different frequency?

1582561295812.png
 

Thread Starter

bignobody

Joined Jan 21, 2020
50
Schematic diagrams of what you have and what you propose to do would make your questions much clearer.
That's fair! @ronsimpson has already posted the original. I've mocked up my proposed additions:

1582565053839.png
I posted the schematic because I can't see the schematic and read your text at the same time.
Do you want 5 Outputs? Each output at a different frequency?
Yes (which I will mix together, schematic not shown), and potentially adjustable frequency on top of what the 8 sequenced pots provide, which is why I also have another 100K pot over each Pitch Oscillator.

Sequencer pots provide the starting voltage, and then each oscillator can be further tuned. I think this will allow me to play chords.

Edit: I should point out that I copied and pasted the Pitch oscillator a bunch of times, so the pin numbers and labels aren't accurate. Assume each oscillator is it's own set of pins and pot.
 
Last edited:

ronsimpson

Joined Oct 7, 2019
439
I think you need one copy of the Oscillator and 4040 and 5 copies of the 4051 and 40106.
The note/tone is set by RVAR2 through 9 and C2.
Adding the 4069s will not work.
1582570324766.png
 

ronsimpson

Joined Oct 7, 2019
439
The pitch oscillator is not digital (1 or 0) but analog.
The signal at the X pins on the 4051 is very different for each pitch oscillator. They need to be kept separate.
 

Thread Starter

bignobody

Joined Jan 21, 2020
50
Sorry, not really following here.

The pitch oscillator is not digital (1 or 0) but analog.
Ok. The CD4069UB is unbuffered. According to the article I read: "The lack of buffering and hysteresis in the inverter lets us use the individual amplifiers for analog purposes rather than digital / logic. ".

So am I not trying to use an analog buffer for an analog oscillator?

The signal at the X pins on the 4051 is very different for each pitch oscillator. They need to be kept separate.
I am not clear why this would be different. If I want all the oscillators playing the same pitch, wouldn't this need to be the same signal for all?
 

ronsimpson

Joined Oct 7, 2019
439
If I want all the oscillators playing the same pitch
adjustable frequency on top of what the 8 sequenced pots provide, which is why I also have another 100K pot over each Pitch Oscillator.
You want all five outputs to have the same pitch but you want them to be different. ??

I removed the 4052 to make it simple. Here the 5 outputs have the same note.
1582595472573.png
 
Last edited:

Thread Starter

bignobody

Joined Jan 21, 2020
50
Apologies for the confusion.

I do in fact mean both, just happening at different stages.

Just talking about the signals from the CD4051, X and the Switching signal that goes through the sequencer pots, this should always be the same for all of the signals going to the 5 oscillators. This is why I thought using a buffer would be appropriate.

For the next stage, each oscillator has an additional 100K pot between the pins. I consider this a "tuning" pot where I can lower the note if I choose by adding more resistance, or I can leave it open and get the original signal. This works on my single oscillator breadboard version - I can have the sequencer create a melody, and use the tuning oscillator to change the overall pitch of the melody.
 
Last edited:

Thread Starter

bignobody

Joined Jan 21, 2020
50
Thank you for your time and input. I still can't logically understand why my design won't work, but I am prepared for it to fail when I get time to try it.
 

ronsimpson

Joined Oct 7, 2019
439
Give it a good try. I am willing to help.
I have waveforms here. I am using a different IC but about the same.
Output is in green 0V to 5V square wave. The blue trace is the input to the 40106. You probably know all this but I thought I would share.
1582605090791.png
 

Thread Starter

bignobody

Joined Jan 21, 2020
50
Give it a good try. I am willing to help.
Thank you, again! I spend 4 hours out of every week day commuting to my job, so mostly only get to experiment on the weekends. During the week I read, review notes, and make plans. I will try this out as soon as I can.

You probably know all this but I thought I would share.
I did not know this. I am still a beginner and don't even have an oscilloscope yet, so I appreciate you sharing.

I have waveforms here. I am using a different IC but about the same.
This sounds promising. I will post my results once I have had time to try it. Cheers!
 

Thread Starter

bignobody

Joined Jan 21, 2020
50
Had a bit of time tonight so I added a cd4069ube to my breadboard circuit and tried to have it drive just a single oscillator. You were correct on both accounts - that there is a signal, and that overall the idea does not work.

I can hear a tone but the different pitches of the sequencer are no longer heard. I can hear a faint pulse in the tone that I suspect corresponds to the switching signal, but that's it. So, the original purpose of the sequencer is lost.

Thanks for your time!
 

Thread Starter

bignobody

Joined Jan 21, 2020
50
I still can't logically understand why my design won't work, but I am prepared for it to fail when I get time to try it.
After failing and thinking about this for a while, I think I understand:

There are two wires from the CD4051, from the X and Switching output to the input and output of the pitch oscillator. As the capacitor driving the pitch oscillator charges and discharges, current will alternate direction through those wires. The 4069 inputs and outputs will not allow current to flow both ways, and thus blocks the alternating current.
 
Top