Sunday, 1 August 2021

Wednesday, 28 July 2021

Digital Filter Build - NLC - Part 2

 This is part two of my Digital Filter Build.
It's a Nonlinear Circuits module in Eurorack format.
The first part of the build can be found here:

This is the build so far.

Adding caps.

Headers next to connect the two pcbs


You're pretty much done


You can find more NLC builds here.

Monday, 26 July 2021

Happy TR-727 day

 It's the 27th of July
A great reason for breaking out the Roland  TR 727

The drum was released in 1985.
It's  the Latin version of the 707.
 It's very much to Roland's credit that they had the courage to produce a drum back in the 80's which broke the mold. With effects, this drum can do wonders.
I have two 727s - one is circuitbent
The circuit-bent one was modified over a decade ago when they were cheap and no one wanted them. 
Though it's really good for tribal beats, the prices for these have gone through the roof so I wouldn't mod one today. But you will discover that with a little reverb or distortion the sound of an original stock machine is completely changed.

Just like on the Roland Tr-707 there are volume sliders for each voice.

Flam, shuffle...... all the usual TR-programming features. Sounds great for additional
percussion with another drum. This will spice up any track.

The sounds are all sample based.

Voices include:
Hi Bongo
Low Bongo
Conga - Mute, Open, Low
Timbale - Hi, Low
Agogo - Hi, Low
Whistle - short, long
Star Chime

The trigger out is good for clocking the arp on synths like the Juno 06

There are individual outputs for each sound.
The fact that you've got  all these outs means that you can run these sounds through their own distortion boxes.  

The DYN-Sync to Midi converter is very useful in syncing old roland gear
If you use it as a master clock you can sync your 303, 606 or 808

Tuesday, 20 July 2021

NLC Cellular Automata - Build notes - part 1

 These are my build notes for the nonlinear circuits Cellular Automata module.

This is a 16 cell gate and pattern generator using cellular automata rules 90 & 150.
Rules 30, 90 & 150 appear to be of special interest among many researchers when applied to music as they produce complex evolving patterns from very simple rules.

Much of the primary research into cellular automata (CA) was carried out in the 1940s at the Los Alamos National Laboratory in New Mexico, USA. by Stanisław Ulam and John von Neumann.

They were studying crystal growth and of all things, self-replicating robots.

An early version of this circuit did appear in the NLC 4U panels in sets of 4 cells per PCB. 

This version is different as the cells are in a grid rather than lines, meaning each cell can be affected by the activity of neighbours on up to 4 sides.

There are 3 CV outputs, two based on what is happening on each half of the circuit, one reflects the pattern created by the active cells. Each cell has a gate output.

There are twelve 4070s
These are CMOS quad 2 input EXOR (exclusive OR) logic gates

Next we need four of the 4042's
quad “D” latch IC consists of P- and N-channel enhancement mode transistors.

A latch or flip-flop is an electronic logic circuit that has two inputs and one output
Latch circuits can be either active-high or active-low. The difference is determined by whether the operation of the latch circuit is triggered by HIGH or LOW signals on the inputs. 
D stands for Delay or Data
This is an example of a clocked flip flop
It's symbol is:
There are 2 inputs : Clock & Data.
There are 2 outputs: Q & not Q.

It only transfers data at a certain time of the clock cycle.
When the clock goes high ( 0 or 1) data will be transferred to Q.
When the clock goes low, Q remains unchanged..
 It can be viewed as a delay line.

The D input condition is only copied to the output Q when the clock input is active.
When the clock goes low, the flip flop wont change its state (until another clock high is reached).
It will store whatever data was present on its output before the clock transition occurred.

Board 2
lots and lots of 2.2k resistors

Re the LED resistors:
"RL: These are the resistors for driving the LEDs. As the resistors are shining thru the window on the panel, you want them brighter than usual. For example, if I normally use 10k for RL for a particular LED, I would use 4k7 for the same LED in this module."

I think I'll try 4.7K. 
If you are like me, you may have bought a bunch of LEDs off EBay many years ago and cant remember their specifications. So if the LEDs aren't bright enough, just swap them for a lower value.

Resistors are on both boards.

Caps next.

Dont forget the caps at the back of this board. They are 0605's (25V) only because I ran out of larger ones.

To be continued....


Saturday, 17 July 2021

KORG KPR-77 Drum - getting started tutorial

This is a basic getting started manual on the Korg KRP 77 programmable Rhythm.
It's one of my favorite drum machines. Quite underrated and still affordable. 
It came out in 1983 and was Korg's answer to the Roland 606. 
The mixer however, reminds me of the Roland TR 707.
All the sounds in this baby are analogue & don't sound anything like a 606 or 707 which
is a refreshing change.
Note that there is no midi. It uses Korg's version of DIN sync which runs at 48PPQN
(Roland uses 24 PPQN) but this is easy to overcome with a Arturia Beatstep. 
The trigger outs also sync Korg Volcas really nicely. 
I wouldn't be surprised if some of the KPR's DNA has found it's way into the Volca Beats.

The manual is really confusing and programming patterns is very different to Roland drum
machines.The controls are cryptic and I must admit that understanding the display took 
ages to work out.
So this is an attempt to simplify things.

Playing the instruments

When you first buy it, you will want to hear the individual sounds.
Slide the MODE switch to "Write/Training" to play the instrument pads.

The mixer will control the volume of each sound
 Just 8 sounds

Notice, there is a vol slider for the metronome.


Playing Patterns

The KPR can store a total of 48 patterns.
These are spread over 3 Groups : A, B,C.
Each group can hold 16 patterns

These are accessed with the 16 instrument buttons... called Basic Banks.
These 16 buttons have many functions.

In order to play a stored pattern:
1. push the mode switch to PLAY
2. press a GROUP button (A, B or C) 
3. press a BASIC BANK button (1-16) 
4. press the orange START/STOP button. 
While a pattern is playing you can restart the pattern by , pressing the D.C. button.

(You can combine patterns, but that's for a different post) 


Writing Patterns

Patterns can be written in STEP mode, PLAY (real time) mode, or a combination.
First, choose a bank & erase the pattern

To erase a pattern:
1. Start in play mode
2. Choose the group/bank as above 
3. Switch the MODE switch from play to Write while holding down the chosen BASIC BANK button
4. Hold down the CHAIN WRITE key (legend: ERASE) and
    press STEP DOWN (legend: ALL INST).
5. you should hear a ping sound.

Now that you have created a clean memory slot we need to set 4 basic parameters:
A. Decide whether you want Claps or Cymbals in this pattern
B. Decide whether you want the Toms to be flamed or not,
C. set resolution/ quantisation, 
D. set the length of pattern
A. Claps or Cymbals ?: 
1. hold down the FUNC SET button
2. press BASIC BANK button 15 
3. the legend on the display will show "CLPS" when the Claps will sound instead of a Cymbal.

B. Toms - Flamed or not ?
1. hold down the FUNC SET button 
2. press BASIC BANK button 16 
3. the legend on the display will show "FLAM" when the Toms will play a double stroke.
C. Resolution
1. hold down the FUNC SET button 
2. press instrument pad 11-14 
You can see the resolution under the numbers.
Button 13 sets the quantise to16ths 

D. Length
1. hold down the FUNC SET button
2. press one of the instrument pads 1-8.
    This sets the pattern length in quarter notes (one quarter note to 8 quarter notes). 
   The  no "4" is one bar (I think) 

If you select a length longer than the resolution allows, the "FULL"
indicator will appear to the right of the bar indicators on the bottom
edge of the LCD.) 
The maximum pattern length is 32 steps. This compares favorably with the Roland TR 606 which has a max pattern length of just 16 steps.


There are 2 ways to program your beats: Step time or Real time.

Step Programming & editing

1) Set the parameters as detailed above (select bank, pattern, resolution, length, etc.)
2) Press an instrument key to place it in the pattern. The bar indicator will show you the 
    step to which you're writing. 
    Writing a hit will advance the KPR-77 to the next step automatically 
3) Press the STEP UP & STEP DOWN key to step forward & back through the pattern, 
effectively inserting rests between notes if you're writing to a previously blank pattern.

Thus, you can edit the pattern you/ve just written using the STEP UP and STEP DOWN buttons.
To erase drum strokes from a pattern in step-time again use the STEP UP and STEP DOWN 
buttons to move to the location of the drum stroke.
Then hold down the CHAIN WRITE button (which has ERASE written beneath it).
Now press the instrument button for the drum stroke you wish to erase.

The unique method of representing the drum pattern can make editing seem difficult.
However, to simplify things the drum strokes for a particular instrument can be viewed.
(while in step mode).
1. hold down the BASIC button
2. press the instrument button you wish to edit.
    The display will only show the drum strokes for that instrument 

Real Time programming

1. following the above instructions for setting resolution, length, etc.
2) Press START/STOP to begin.
    You will hear the metronome.There is also an accented ping on the 1st beat.
3) Play the instrument keys. (1-16)
    The KPR-77 will quantize your playing according to the set resolution so 
    you wont get any off time beats.
    (You can watch the step position move on the LCD.) 

To erase any unwanted "hits/strokes" in real time, you need to hold down the CHAIN WRITE (ERASE) key
and the  instrument key in question at the exact time that the pattern passes the undesired hit.
I find this method quite tricky, though you sometimes get happy accidents.
To erase all hits by a single instrument, repeat as above but hold the instrument key down until the
pattern goes through one, complete pass.

Korg index

For more info on the history of Korg Drum Machines Click Here

Wednesday, 14 July 2021

NLC - Digital Filter Simulator - Build notes - part 1

 These are my build notes for the NLC Digital Filter Simulator.

It's a nonlinear circuits eurorack module.
12HP wide

It's mostly an analog circuit using CMOS and op-amps.
Audio is fed into a 4-bit A/D (analog to digital) converter section and then passed through shift registers.
It's then converted back to analog with a D/A (digital to analog) converter.
The output is then fed back into the input.

The module requires a clock.
You can also input CV instead of audio, to create interesting patterns.

Some more pics of the unpopulated PCBs

NLC words of wisdom

The 4015s
Mfr. Part No.

Description:Counter Shift Registers 3-18V Dual 4-Bit CMOS Static Shift
You need 2 of these.
It's the only CMOS section of the module.

The rest of the ICsare mainly op-amps

LL4148 diodes

The power rectifier (you can use a 10R resistor)... to protect the module if it's accidentlyplugged in backwards.

Get those 100k resistors on first.there are 36 of them.

Resistors marked 100k* on the input and output stages can be adjusted for better balance between inverted and non-inverted signals, try 51k. 

The two 470k* on the bottom PCB can also be adjusted to a lower value to get these stages hotter in the mix. They will cause the module to lock up at some settings and you will need to adjust the Range pot to suit, no biggie, nothing gets hurt. 

I'm using a 4.7K resistor for the RL  

To be continued...
Part 2 is here:


You can find more NLC builds here.