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This post was updated on .
Let's see if I can manage to explain a bit about it, based on what I understand...
The main section and at the heart of this Sequencer is the CD4017 LED Driver IC
This is simply put, a 10 channel LED driver that ticks chronologically trough and activate 10 different LED outputs one by one, when receiving a short +voltage pulse to it's trigger input.
It is used in LED clocks to change to the next number, as the seconds tick by...
This is achieved by sending a pulse to the trigger of the 4017, which has it's 10 different outputs connected to a numerical LED.
This Numerical LED has separate lugs for each of the number to be displayed and a common ground, therefore this 10-step IC design. A 0-9 counter...
In this case, the trigger-pulse to drive the steps/outputs of the 4017 in sequences, is generated by the 555 timer, which function as a clock/CV pulse generator, with variable speed capability by changing the frequency of the pulse. The frequency is set by variable resistance via the Speed pot.
Think of this Speed pot as the Speed control for your tremolo!
The RUN/STOP switch simply cuts this signal coming from the 555, so that when the 4017 does not get any new trigger signal (stop position), so it simply stops. It will then continue to the next step in the sequence, where it left off, when the clock signal is returned (run position).
Sending a voltage signal to the re-trig input (actually called "reset"), at the same time as reactivating the clock signal from the 555, will start the sequence from step 1.
All the Step-outputs has their own Step-Sens pot and they all sum up via the (master) Sens pot, resulting in a single voltage output that has a 8-step adjustable pulse pattern with a master Sens pot at it's CV output.
Think of the (master) Sens pot as the Depth control of your Tremolo!
The Step-Sens pots can just as well be 8 compact on/off swithes for simplicity... This will save up a lot of space regarding housing/boxing it...
So far:
So what we now have here, is a very cool programable rhythmical voltage (or Ground) swing that can be put creatively to use.
Specially when we are dealing with circuits that has a LFO driven optocoupler involved.
And this unit now enables us to send out either a positive voltage swing, or a to pull a signal to ground.
We have multiple steps in sequence...
We have control of the tempo of the sequence...
We have control over the depth/sensitivity of each single step in the sequence...
We have a master control to set the Sens/Depth of the Sequence as a whole.
Cool!
Selecting number of steps:
The number of steps can be selected, by connecting "the next number/output/step in the sequence" coming from the 4017, to it's own re-trig input. (the re-trig input is the grey wire that is labeled: "Step Selector Rotary Common" on my layout)
This means that, if you want a 4 step sequence... you then connect the 5th step of the sequence to the re-trig input, as this re-triggers the sequence, and then makes this 5th step, the very first step in the re-triggered sequence. Resulting in a 4-step continuos loop.
So therefore.... by (also) connecting the different/desired sequence step outputs to a switch (I used a rotary switch for this) with it's common going to the re-trig input.
You can then use this switch to set the desired amount of steps in the sequence, by sending the "next numbered step/output" compared to the desired number of steps you want, to the re-trig input of the CD4017.
So... Want 4 steps? connect step 5's output to the re-trig
Want 7 steps? connect step 8's output to the re-trig
See the pattern going...? use the next number in the sequence to set the desired number of steps that you want.
Adding a switch here, is a modification that I did to the Baby-8, in order to free it from being locked down as just a 8-step sequencer.
Now it can do a 1-step pulse, or up to a 10-step sequence. Each with it's own seperate Sens/Depth pot (or on/off switch) in addition to the Main Sens/Depth pot.
Making it useful for both extremely fast ringmodish 1-step tremolo stuff, ...to a mellow 9-step and complex wah pattern, all depending on what you hook it up to.
Synch and Chaos:
By having the "Ext Clock In" option that I added on the layout, it is then possible to take a clock signal from an external unit, and feed it to the "Ext Clock In" of the Baby-8, thereby bypassing the 555 clock/timer.
A "Random" mode can be achieved/added to the circuit, by sending continuous voltage to the re-trig input, this seems to confuse it, and make it sputter out pulses very fast and sputtery.
I'm considering running a wire from the +9v DC input to a 2 pole momentary stomp switch (normally off) and to the re-trig input
So...
How to use and implement it with other stuff?
I do not know all ways to use this, but here is how I look at it:
The output from the Sens pot is your LED-driving pulse. You can also look at it as a CV signal (a control voltage that can be used with analog synths that has CV-inputs, Gate-Inputs and similar), cause that's what it actually is... (has a range from 0v to about 6v if I remember correctly)
Since this unit is a sequencer that puts out voltage, we then have something that we can call an Sequenced LFO to drive an LED/Optocoupler, meaning that it can be used to replace the LFO in many circuits.
In this layout, it basically hooks up where the LFO signal hits the + side of the LED of the chosen effect's Optocoupler.
If you add a optocoupler at the end of this signal, you can then get variable resistance coming out at the other end, instead av a voltage swing. Meaning: you have a swinging Ground signal instead. And that is what is used to make a tremolo; it simply pulls the signal to ground/turns down the volume in pulses.
So that gives me a couple of ways to use this Sequencer:
One is to send voltages in patterns, as a LED driver, and
One is to pull signals to ground in patterns
I can also send and receive clock/tempo signals
By adding a Octocoupler to a Wah circuit (instead of the treadle-pot) you will have something in the style of a SeekWah.
Replace the Wah with a Tremolo circuit, you have something like the SeekTrem.
How about hooking it up to a Phaser or a Univibe style circuit?
Chorus?
Reverb and Delay modulation?
CV and Clock potentials:
This kind of sequenced LFO can also be a very nice tool that can enable you to merge your guitar effects and their control parameters, with your analog synth rig, your drum-machines and sequencers, since these units often can send and receive both CV signals and clocks between each other.
- You can then, as an example; send a CV output signal from your pedalboard to the synth and apply the same pattern to the modulation of the synth's sounds as the one you have going on your 7-step'd psychedelic auto wah from your pedalboard.
- Or you can get a clock pulse from the main sequencer/pro-tools rig, and have your sequence in synch with the main-sequencer, at all times. The need for tempo adjustments between songs can be replaced with a clock signal, either if it is coming from an old unit with a CV/Clock output, or via a jack from the sound-card of a DAW.
I see many potential uses for this circuit, and the idea of building many (LFO-free) modulation effects in rack units, and then add units with this sequencer + different LFO's that can be patched to these different modulation effects,...
Well... It starts to intrigue me!
Specially for the recording studio!
An old style modular synth approach to guitar modulation effects, with endless patchability....
I hope this helps you to understanding this kind of circuit, at least it is an attempt to describe how I see it...
If someone now could crack the code on how to get a tap tempo control added to it without a shitload of circuitry, then the possibilities would become very interesting...
A very simplified Taptation replacing the 555 maybe...?
Definitely something worth considering...
Cheers!
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