Sequencer Nostalgia

This was my first build when I came back to SDIY. A three row/16 step sequencer. Completely build on stripboard. Still working after all this years. Only hand sketched schematics. Nothing to publish. Pictures only.

Sequencer three rows/16 steps: front
Sequencer three rows/16 steps: front
Sequencer: Clock close up
Sequencer: Clock close up front
Sequencer: Clock close up back
Sequencer: Clock close up back
Sequencer: Inside
Sequencer: Inside
Sequencer: Inside
Sequencer: Inside

ADSR Euro-rack

ADSR: Front view
ADSR: Front view

This is another derivation off the ADSR for my NGF-E project, adapted to 12V Euro-rack format. Because this one is a stand alone module I have removed all additional features from the Next Generation Formant project. Nonetheless it is still based on original Elektor Formant ADSR schematic. I made some error corrections and added my changes to the design. All parts are updated to today (2021/01) available parts. I have made a few changes to fix some shortcomings of the original. A triple range switch was added for finer adjustment of the ADSR CV-output signal. The attack rise time is shorter now as in the original. The gate input is buffered. The fixes a fault in the original when working with analog sequencers. The output voltage is slightly raised to reach really 5V. Due to the design of the original Elektor Formant ADSR the output of the original ADSR keeps a residual voltage of about 0,5V. I have put an compensation in my design to correct this. The driver circuitry for the output indicator LED is changed for better linearity.

Specs and features

  • AD/ADSR switch
  • Gate input 5V
  • CV output ..5V
  • CV output indicator
  • Range switch: fast, middle, long
  • Attack (A) 0,5ms…16s
  • Decay (D) 4ms…40s
  • Sustain (S) 0..5V
  • Release (R) 4ms..40s
  • Power consumption below 15mA each rail

The documentation and the Gerber files for download can be found in my website.

ADSR: Schenmatic main PCB
ADSR: Schematic main PCB
ADSR: Schematic control PCB
ADSR: Schematic control PCB

This is a close clone of the Elektor Formant ADSR. Here i only describe the changes i have made. The description of the other parts of the circuitry can be found in the original Elektor Formant documentation. The gate signal input resistance is raised from 33kOhm to 1megOhm with the input buffer IC1A. This protects against double triggering with the falling edge of the gate signal when using sequencers. R30 is used to fix the input to a defined potential when no signal is attached to the input. C1 was lowered to 6n8 from 10nF. In combination with C2 and the raised charging voltage through IC1B/R9 this makes for faster attack time. The load capacitor of 10u was replaced with three selectable capacitors of 2,2uF 4,7uF and 10uF. This makes for a finer adjustment of the response times of the ADSR. The voltage divider R19/R21 was adjusted to ensure that the output level of 5V is reached. If this feature is not used R25 should be lowered to 5k1. Construction conditioned the output at IC1D only reaches a minimal voltage of about 0,5V. To compensate for this i added IC2A. If the ADSR is not used the output voltage is now at -0,5V. The current consumption was lowered with using the TL064 and a low current LED.

ADSR: back view
ADSR: Back view
ADSR: Populated main PCB
ADSR: Populated main PCB
ADSR: Populated control PCB
ADSR: Populated control PCB
ADSR: Side view
ADSR: Side view

Signal to Trigger Converter

Signal to Trigger Converter: Front view
Signal to Trigger Converter: Front view

This module was originally build for my Shakuhachi to Synth project to provide the start/stop pulse for the Pitch to voltage converter. But it turned out to be much more useful. When you have the basics for your synthesizer like VCO, VCF, VCA, ADSR, LFO,… and some controllers and you want more, then using your keyboard to steer the synthesizer it is time for some modules to produce trigger signals out of different sources. Here is one of them. A signal to trigger converter. You can feed in a changing signal and every time the signal went through zero a trigger is generated dependent on the direction from where the zero point is crossed. You can add a threshold manually or CV controlled to move the zero point up or down as well. You can feed the signal in through input one ore two. When both inputs are used the signals are added together. When the signal crosses zero from positive to negative a trigger of about 0.1msec is generated at output -Trig. When the signal crosses zero from negative to positive a trigger of about 0.1msec is generated at output +Trig. Output +/-Trig provides both triggers. This output can be used to generate interesting rhythmic patterns when the threshold is set by a slowly moving CV or some DC offset is applied to the signal.

Specs and features

  • Two added inputs
  • Threshold manually and with CV
  • Output for +Trig, -Trig and +/-Trig: 0.1msec
  • Runs on +/-15V and +/-12V with minor resistor changes
  • Power consumption below 25mA each rail

The documentation and the Gerber files for download can be found in my website.

Signal to Trigger Converter: Schematic control board
Signal to Trigger Converter: Schematic control board
Signal to Trigger Converter: Schematic main board
Signal to Trigger Converter: Schematic main board
Summed signal to trigger
Summed signal to trigger

The incoming signals are summed up. Every time when the summed signal changes polarity (moving through zero) a trigger is generated. Moving from plus to minus generates a trigger at the negative trigger output, moving from minus to plus generates a trigger at the positive trigger output. Trigger length is about 0.1msec.

Screenshot sine to trigger
Screenshot sine to trigger

The uppermost line (Yellow) shows the input signal. The second line (Blue) shows the trigger when the input signal moves to the positive site. The third line (Purple) shows the trigger when the input signal moves to the negative site. On the fourth line (Green) you can see both triggers added. This picture is taken without any threshold.

Signal to Trigger converter: Back view
Signal to Trigger converter: Back view
Signal to Trigger converter: Side view
Signal to Trigger converter: Side view

Passive Multiple

Passive Multiple: Front view
Passive Multiple: Front view

Just another often needed utility module. A passive multiple.

Specs and features

  • Seven passive parallel in/outs
  • No power connection

The documentation and the Gerber files for download can be found in my website.

Passive Multiple: schematic
Passive Multiple: schematic
Passive Multiple: back view
Passive Multiple: back view
Passive Multiple: Side view
Passive Multiple: Side view

Buffered Multiple

Buffered Multiple front view
Buffered Multiple front view

This is a useful and often needed utility module. The input voltage is precisely reproduced on the outputs. It comes in handy when you need to distribute signals which must be decoupled. The input signal is buffered and decoupled with means of individual operational amplifiers. One input drives 6 individual outputs. The accuracy depends on the used operational amplifier. For pitch CV I recommend precision OpAmps like the LT1014 (quad) and LT1013 (dual).

Specs and features

  • 6 independent buffered outputs
  • Runs on +/-12V and +/-15V
  • Power consumption below 10mA each rail

The documentation and the Gerber files for download can be found in my website.

Buffered Multiple schematic 01
Buffered Multiple schematic 01
Buffered Multiple schematic 02
Buffered Multiple schematic 02
Buffered Multiple side view
Buffered Multiple side view
Buffered Multiple side view
Buffered Multiple back view
Buffered Multiple populated main PCB
Buffered Multiple populated main PCB

Quad white and colored noise source. Quad random voltage source

Quad white and colored noise source. Quad random voltage source. Schematic control PCB
Quad white and colored noise source. Quad random voltage source: Front view

It is quite useful to have different adjustable noise and random voltage sources. Depending on your patch stile of course. Here is the quad version of my noise module from the NGF project. It is a combination of two original Elektor Formant modules. The noise module from Elektor Formant book one and the colored noise (CNC) module from book two. It provides four independent white noise outputs, four adjustable colored noise outputs with “red” and “blue” adjustment. The four random voltage outputs are adjustable in speed of change. The noise is derived from the reverse biased BE diode of an NPN transistor.

Specs and features

  • Four independent white noise outputs
  • Four independent adjustable colored noise outputs with “red” and “blue” adjustment
  • Four random voltage outputs, adjustable in speed of change
  • Four LED indicating the random voltage change
  • Runs on +/-12V and +/-15V
  • Power consumption around 65mA each rail

The documentation and the Gerber files for download can be found in my website.

Quad white and colored noise source. Quad random voltage source. Schematic control PCB
Quad white and colored noise source. Quad random voltage source: Schematic control PCB
Quad white and colored noise source. Quad random voltage source. Schematic main PCB
Quad white and colored noise source. Quad random voltage source. Schematic main PCB

Description:

(Given for one of the four.) Noise source is the reverse biased BE diode of NPN transistor Q1 (B_090). The following operational amplifier IC1A and IC1B (B_090) amplifies the noise to 10Vpp. IC1C (B_090) is the buffer for the white noise output. IC2B (F_101) is configured as a 12dB low pass. So you get a low frequency random voltage. The changing speed is set with P3A/P3B (F_101) which sets the corner frequency of the low pass filter. IC2A / LED1 (F_101) makes the fluctuation visible. TR_1 (F_101) adjust the brightness of LED1 (F_101). In the feedback loop of IC1B (F_101) is an adjustable filter combination which gives you a wide range of adjustable colored noise with P1 and P2 (F_101). The output is buffered with IC1A (F_101).

Quad white and colored noise source. Quad random voltage source. Populated control PCB
Quad white and colored noise source. Quad random voltage source. Populated control PCB
Quad white and colored noise source. Quad random voltage source. Populated main PCB
Quad white and colored noise source. Quad random voltage source. Populated main PCB

12V to 5V gate converter

12V to 5V gate converter schenatic
12V to 5V gate converter front panel

This utility module converts a 12V gate to a 5V gate. It is needed when you have a module with 12V gate output and your receiving module only accepts 5V gate voltage.

Specs and features

  • Converts 12V gate to 5V gate
  • Runs on +/-12V

The documentation and the Gerber files for download can be found in my website.

12V 2 5V gate converter schematic
12V 2 5V gate converter schematic

The 12V input is divided down with the input voltage divider to 5V and buffered.

12V 2 5V gate converter populated PCB
12V 2 5V gate converter populated PCB
12V 2 5V gate converter side view
12V 2 5V gate converter side view

Trigger Delay

Trigger Delay front

Trigger Delay front

This module can delay an incoming trigger signal up to 8 seconds. The trigger length is adjustable up to 8 seconds as well. The trigger pulse length is independent from the input signal length. Both parameters are independently adjusted with potentiometers. The output state is shown with a LED.

Specs and features
• Input: positive Trigger or any fast changing voltage.
• Output: 5V pulse with adjustable delay and length.
• PSU +15V/-15V or +12V/-12V

The documentation for download and the Gerber files for download can be found in my website.

Trigger Delay schematic

Trigger Delay schematic

Trigger Delay populated PCB

Trigger Delay populated PCB

Trigger Delay back view

Trigger Delay back view

Clock Divider with prime numbers

Clock Divider with prime numbers

Clock Divider with prime numbers

This clock divider divides the incoming clock signal down to the prime numbers /11, /13, /17, …. /31. The output is a 5V positive pulse. The length of the incoming pulse is kept. The trigger is on the rising edge of the incoming signal. The reset input can be used for syncing with other clocks. All outputs are buffered and brought out parallel with LED signaling the pulse.
Specs and features
• Regular input clock/square wave +5V
• Input signal divided by prime numbers
• Output +5V pulse with the length of the input signal (pulse)
• Runs with +15V/-15V or +12V/-12V (with minor changes)

The documentation for download can be found in my website.

Clock Divider with prime numbers, schematic

Clock Divider with prime numbers, schematic

Most work is done by the microprocessor. The micro takes care of the input and output timing. All outputs are independently buffered. The clock is made visible with LED.

Clock Divider with prime numbers, populated PCB

Clock Divider with prime numbers, populated PCB

Clock Divider with prime numbers, rear view

Clock Divider with prime numbers, rear view

Logic Module

Logic Module front

Logic Module front

I needed a module to combine gate and/or trigger events for steering sequencers, ADSR and other gear. So I build one. This one here has and, or, ex-or and neg logic gates. The states of the inputs and output are signaled with LED. The inputs takes audio as input as well. This makes for some interesting patches. The minimum input level can be set to your needs.

The documentation for download can be found in my website.

Logic Module schematic p. 01

Logic Module schematic p. 02

Logic Module schematic p. 02

Logic Module populated PCB

Logic Module populated PCB

Logic Module back view

Logic Module back view