Friday, 3 July 2020

Synthesizer Logic Modules - The 7 gates

Logic gates are great ways to create interesting rhythms or combine triggers from various sequencers.
Recently I've been using them to trigger drum modules.
Some logic gates also work at audio ranges.
There are 7 basic gates: OR, XOR, AND, NOT (inverter), NOR, XNOR, & NAND.

To make things even simplier, the 3 basic fundamental gates are OR, XOR, AND.
They use the inverter (NOT) to make NOR, XNOR, & NAND.

OR gates
Output a high signal whenever one or more of its inputs are high.
Useful if you wish to combine several gate signals into one.
You can use this instead of a mixer or multiple.

 In1 In2 Out
 0         0 0
 1 0 1
 0 1 1
 1 1 1

XOR Gate (Exclusive OR gate)
Will only output a high signal when one input is high and the other is low.
It allows the signals to pass Except when they happen simultaneously.
It's like when 2 people try to squeeze through a narrow door at the same time.
(use this for your two snare drums - to prevent them triggering simultaneously)

 In1 In2 Out
 0         0 0
01 1
 1 0 1
 1 1 0

AND gate
Outs a high signal when all its inputs are high.
(If only one input is high it will output a low signal)

 In1 In2 Out
 0         0 0
 1 0 0
 0 1 0
 1 1 1

NOT gate
The above 3 gates are available as inverted versions (N = not):

 In Out
 1 0
 0 1

OR -----> NOR
XOR -----> XNOR
AND-------> NAND

NOR Gate
This is a OR gate followed by and inverter.
This is quite a useful gate to have, as it's possible to build the other basic logic gates
using only NOR gates.

 In1 In2 Out
 0         01
 0 1 0
 1 0 0
 1 1 0

Its output is "true" if both inputs are "false." Otherwise, the output is "false."

This is a XOR gate followed by an inverter

 In1 In2 Out
 0         01
 0 1 0
 1 0 0
 1 1 1

This is a AND gate followed by an inverter

 In1 In2 Out
 0         0 1
 0 1 1
 1 0 1
 1 1 0


For most Eurorack modules:
Low signal = 0V to 1V (usually)
High signal = greater than 1V to 5V (Usually)

Many logic modules respond to continuous CVs like LFOs .
They are reading the CV as a high gate when it exceeds 1V (usually) and a low gate when it is below.
So they can be used as comparators with a fixed threshold.

The logic synth modules you can buy or build will either use discrete diodes, transistors & resistors,
or use integrated circuit chips. TTL and CMOS are the most common types of ICs.
TTL IC’s may often be labeled as the 7400 series.
CMOS ICs are commonly marked as 4000 series.

Eurorack Logic Modules
+ Elby ED132 - Boolean Logic (Also a Serge Version)
+ Erica Synths - Pico Logic
+ Mystic Circuits ANA
+ Intellijel OR, Plog, Spock , uMod II
+ AniModule  LogicOgic, XX_OR
+ 2HP - Logic
+ Mutable Instruments - Kinks (OR & AND gate)
+ Doepfer A-166 (Dual Logic Module) .... AND, OR & NOR, plus two inverters.
+ NLC - Bools, Neuron, Chopper, 8 bit cypher,
+ CGS Funky Drummer
+ CGS Boolean Logic
+ EMW Logic 101, Logic 202
+ Snazzy FX Ardcore
+ Synthrotek - Either-OR Eurorack OR Module
+ Pittsburgh Modular - Logic Banks
+ Analog Ordnance - Logiplex, OR gate,
+ Ladik B-010 Bool2, B-020 Bool3,
+ Circuit Abbey - ANDY, ORY, XORY, VERTY
+ Synth Cube Dual Logic
+ LZX - Castle 100, Castle 101
+ Pulp Logic (1U tiles) -Logical AND, OR, Diode-OR, XOR

Plog - Intelligel
This has AND, OR, NOR, XOR, NAND, and XNOR gates


Fairlight IIx - instructions for using the HxC SD reader

The  HxC SD card reader is an excellent addition to your old Fairlight.
The HxC is a Floppy drive emulator.
The Floppy disk drives are 40 years old and hard to maintain, repair & replace.

I highly recommend you email Jean-Bernard of MUSTUDIO for one.

I purchased the kit from
Many thanks also to Peter W for his help in it's installation.
The Flash player uses a SD card to emulate 2 virtual drives. (A & B).
Compatable cards are SDHC up to 32MB.
Formated in FAT 32.... use a PC (not a MAC) to format the card.

I found navigation of the file structure in the SD card a bit confusing at first.
This is how it seems to be set up:

You only need to use the "Systems" and the "sounds" sections.

The 2 toggle switches must be in the correct position.

I like to configure the system to use two virtual drives.
That is, I'll bypass the use of the Floppy Drives completely.
Left switch : up
Right switch : Down

1. Turn on the Fairlight.
    The monitor will as is usual display "Load System disk in drive"

2. "Systems" should be shown on the display.
      If not, use the left/right buttons to rectify till you find "systems".
      (pressing the left/right buttons will move you between Systems, Sounds & QDOS)

3. Hit enter when you see "Systems" (the centre red button)
4. Using right button, step through till the desired software is shown.
    (Revision 20). Hit enter.

    The Fairlight will now load the operating system
    It bleeps as it steps through sectors. The monitor should eventually show Page 1

5. Hold down "Enter" (middle red button) for a few seconds.
    The LCD will change... You are entering the "Function Menu" Mode.

6. Toggle through options till "change drive" appears.
     Hit "Enter"

7. Toggle until "B" appears.

    Hit Enter

8.  The LCD display will show the software revision.

     Toggle left until only dots appear.

9. Systems should reappear.   

10.  Toggle left till "sounds" shows.
       Hit enter

8. Step through till the desired library is found. (I normally use 1.3)
    Hit enter

9. On the Fairlight itself, go to page 2.
    You should see displayed the contents of the virtual disk.

10. Toggling left & right should show the contents of each virtual disk.

This is library (or virtual disk) 15

Test by loading a file.
Type L,A,filename<return> to load a file.

eg to load a file named GONG1.VC
type L,A,GONG1 <return>
You don't need to add the .VC after the file name. 

Wednesday, 1 July 2020

Roland / Studio Electronics SE - 02 envelope

I'm revisiting my SE -02 synth .
The Studio Electronics / Roland Boutique synth has a rather unusual envelope, which is kinda borrowed from the Moog Mini D.
It's not a clone of the Moog, though I thought it would be useful to compare the two.

The most common type of envelope is the ADSR.

It has 4 stages. The stages are:
Attack : is the time taken from nil to peak, beginning when the key is pressed.
Decay : is the time taken from peak to the sustain level.
Sustain : is the level during the main sequence of the sound's duration
Release : is the time taken from the sustain level to zero after the key is released

The Mini Moog D was unusual in that there were just 3 knobs to control a 4 stage envelope.
Most synths have 4 knobs.
Attack, Decay & Release are all time based.
Sustain is a voltage level. It is usually "flat" and does not change during it's phase.

Usually the envelope starts with a signal from a keyboard or other source. It goes through the attack & release stages. When it reaches the sustain phase, it pauses and remains there until the gate goes low (e.g., from the keyboard key being released).

There were two identical envelopes ...  one for the filter, and one for the amplifier

The decay knob doubles as the release knob.
So the envelope can be seen as a ADSD envelope.

It's interesting though not surprising that Studio Electronics decided to use a similar envelope configuration.
My SE-MidiMoog (which is a rack mounted Model D) started this all off.

The SE-01 & SE-1X saw the return of that release knob, but the SE02 saw it's demise once again.

Maybe the decision to drop this pot, was based on practical considerations like the lack of space on the Roland Boutique synths.


So looking at the front panel of the SE 02 one can see we have 2 envelopes:
A Filter and a Amp envelope.
Neither envelope has a release knob. They both however share a release switch
which is in the the lower right corner.
It's settings are: 2, 1&2, OFF
2 = The release stage is applied to the Amp
1&2 = The release stage is applied to both the filter & AMP
OFF = No release stage

Remember that the decay value = release value.

About the other knobs & switches in the Filter/Envelope section:

Key Track
1/3  = The filter frequency changes by 1/3 of the pitch change.
2/3  = The filter cutoff frequency changes by 2/3 of the pitch change.
          If both switches are on, the filter cutoff frequency changes by the same amount as
          the change in keyboard pitch.

Adjusts the amount the filter envelope effects the filter frequency.

Normal / Invert switch
Specifies the polarity of the filter envelope that is controlled by the [CONTOUR] knob. If this is set to “INVERT,” the polarity is inverted.

Mtrig switch
If this is on, the filter envelope restarts each time you press a key.

Specifies the signal that controls the amp envelope.
LFO: The LFO controls the amp envelope.
GATE: The Note or Gate controls the amp envelope


Studio Electronics SE -02 / Roland - Transposing sequences with the keyboard

The manual is a little confusing.

When I first attached a keyboard to the SE-02, it appeared thAT i couldn't transpose
any stored sequences.

To do this you need to enter SETUP.

While in sequencer mode
1. Press NOTE & GATE simultaneously
2. Press the 3rd STEP button
3. Rotate the VALUE knob till the display shows trn (The default is OFF)
   trn = transpose
4. Press the VALUE button (3 times)
    You will be prompted with the message "sure",...

Pressing this "value" knob is also how I save patterns.
The presets occupy memories 0-87.
88 is clear for your first patch.

The problem with this method is that the sequence will only sound while you are pressing a key.

A second method for transposing the sequence is
1. start playing your sequence while in SEQ mode.
2. Switch to PATCH mode while the sequence is still running.
3. press the TRANSPOSE button
4. Press OCT- or OCT+ to transpose up and down an octave

Saigon War Remnants Museum -Vietnam

This was first opened just after the end of the Vietnam War in 1975.
It was originally called the ‘Museum of American War Crimes’.

Quite a confronting place.

The effect of war on both the combatants and civilians is brutally displayed.
I left with a feeling of intense sadness.

For war memorabilia enthuasists there is lots to see ... helicopters, tanks, fighter aircraft.. etc

But the photos upstairs in the building tell another story... the human cost

For more travel postcards click here:

Wednesday, 17 June 2020

Moog 911 - Envelope Generator

Moog 911 Envelope Generators need S-triggers to start their cycle.
Moog's designers wanted people to be able to plug in a simple foot switch to trigger sounds, 
The original design of this module is from around 1968. 

The Moog 953, 952 or 962 Keyboard will produce S-triggers.
"So will Moog Ribbon Controllers, Percussion controllers , Sequential Controller Complements and Envelope Followers" (Moog Manual)
In comparison,  V-triggers start at zero volts and rise to a standard level .. usually 3V.

Trigger Input : Switch Trigger
Output Impedance 10K ohms
Time range on T1, T2, T3: 2 milliseconds to 10 secs.
Peak DC output on Esus : 5.5V (+/-10%)

The 911 plugs into the Moog modular using a 22 pin PCB/edge card connector.
It's a ADSR envelope generator.
The pin out is as follows:
1. +12V at30mA
2. GND
3. -6V at 15mA
14. Trigger out
15. Shield
21. S-trigger in Trigger switch (Jones S-302)
22. Shield

The Moog manual suggests a regulated AC supply, such as a Moog Model 901 or dry batteries.
Max current is 50 milliamperes.
Range of T1: 10 ms to 10 secs (attack)
Range of T2: 10 ms to 10 secs (delay)
Range of T3: 10 ms to 10 secs (Release)
Range of  Esus:  0 to Emax
Esus = sustain.
Emax = voltage at which T2 begins. = 5.5V +/- 10%

You trigger the 911 by closing a switch. So unlike most EG's you will encounter today, no voltage is supplied to trigger the module ... its quite the opposite.

You need a 916 interface to convert CVs to S-triggers

" the 911 Envelope Generator produces a single voltage contour whose time/voltage variation
 is determined by potentiometers T1, T2, T3, and a time constant sustaining level potentiometer (Esus).
Closure of the input trigger switch directs the voltage contour to T3 (final decay) regardless of
what stage (T1, T2 or E) was in current operation."
                                                                                                              (Moog Manual)

"The 911 Envelope Generator completes one of the most important musical functions:
That of producing a variable one-shot control voltage contour in time.
This output is thus capable of controlling any voltage controlled module – most notably
a Voltage Controlled Amplifier – resulting in the articulation of a single sound."

                                                                                                                 (Moog Manual)

A common module to pair with the 911 is the 911A - The Dual Trigger Delay.
This can create multiple or combined DC voltage contour outputs.