Nonlinearcircuits SPASM Manuale utente
nonlinearcircuits
SPASM build & BOM
This module takes the classic Sprott jerk circuit and replaces all the
resistors with LDRs.....a 7 way vactrol. This means the brightness of
the LED in the giant vactrol controls the frequency of the circuit.
It is a very easy build and will give you a very flexible chaotic
circuit. The CV inject jack allows you to control the chaos with gates
and CV, some signals will cause it to pause or stall, others will make
it glitch & freak out. CV freq controls the LED which, in turn, controls
the resistance in the LDRs.
It is a very flexible build; you can use any LDRs you like, so long as
they are the same. You can also use any capacitors you like for CAP, so
long as they are the same.
Of course, the LDRs and capacitors you choose will affect the behaviour
& frequency range of the circuit. GL5516 LDRs go to 500kΩoff resistance
whereas GL5549 go to 10MΩ+ (anywhere from 10MΩ to 20MΩ), so will be a
lot slower but will give a much wider frequency range and some very
unpredictable outputs. Similarly with capacitors 10uF will be a lot
slower than 10nF.
If going for the more extremely slow values, GL5549 LDRs and 10uF caps,
the module will stall at minimum pot settings and generally needs a CV
on the CV freq input to make it operate. This is actually a good thing
as you can turn the signals on and off with CV or gates.
Please note the build pictures below when constructing to make the box
fairly light-proof. A bit of leakage does not seem to matter much but
you could add a bit of black silastic sealant around the edges if you
really want to, I have never bothered. When soldering the connector pins,
use the SIP connectors, jumped across 1 or 2 pins (see pics) to ensure
they are nicely perpendicular to the PCB. When soldering the PCB to PCB
connectors, I press lightly on the PCB to help keep the connectors tight
against the board.
If you find the Spasm is being affected by reflections from flashing
LEDs from other modules in your case; either take the view that it saves
you a patch-cord, or place 2 pieces of black electrical tape across the
PCB where the vactrol box is.
Also, please note the pots go on the side of the PCB that has the pot
symbol screenprinted, this is different to previous NLC PCBs……just look
at the pictures, if you have time and it isn’t too much trouble.
BOM –The Tayda part numbers are given as examples, feel free to buy
from your favorite retailer if you prefer.
VALUE
QUANTITY
DETAILS
CAP
3
0805 see intro notes
10µF
2
0805 OR 1206 25V rating or higher
RL
1
0805 resistor for panel LED, select
to suit brightness (best to use a
superbright LED and at least 10k)
RLbox
1
0805 resistor for black box LED,
select to suit brightness (1k-10k),
probably 1k-2k2 will be good
1k
4
0805
100k
4
0805
330k
2
0805
TL072 or TL082
3
soic Tayda: A-1139
LL4148 diodes
2
light dependent
resistor (LDR)
7
SEE INTRO TEXT. THESE GO ON THE
BOTTOM OF THE UPPER PCB
LED for vactrol box
1
3mm best, diffused Red, green or
yellow. THIS GOES ON THE BOTTOM OF
THE UPPER PCB
LED for panel
1
5mm –superbright or similar
100k (B) pot
3
Tayda: A-1848
100k –1M pot (A or
B...whatever you have)
1
Feedback pot. If building a very
slow version, a 1M pot is better but
not essential.
Eurorack 10 pin power
connector
1
Tayda: A-198
Schottky, power
rectifier or 10R,
optional - for reverse
voltage
protection...or not
2
SMD, Schottky (best option) or
standard power rectifier diode 50-
600V 1A or more, dot on PCB
indicates CATHODE (stripe on
component) Or use a resettable fuse
or just a 10R. SEE NOTES #1
3.5MM SOCKET Kobiconn
style
6
Tayda: A-865 or preferably get
Thonkiconn Jacks (PJ301M-12) from
Thonk or Modular Addict
10 Pin 2.54mm Single
Row Pin Header Strip
5
Tayda: A-197 (cut to size)
10 Pin 2.54mm Single
Row Female Pin Header
5
Tayda: A-1306
Additional notes:
1. Some power diodes: PMEG2005EGWX SCHOTTKY RECT, AEC-Q101, 20V, SOD-
123, PMEG2005EH DIODE, SCHOTTKY, 0.5A, 20V, 1N400x or S1JL or
similar
2. The resistors, caps and transistors are cheapest from Tayda. Diodes
from Mouser/E14/Farnell/etc.
3. Join the Nonlinearcircuits Builders Guild on FB:
https://www.facebook.com/groups/174583056349286/ and ask questions
there if you have any. If you prefer not to FB then email is fine.
4. When soldering on the pins, use the SIP connectors to hold them on
straight. This pic below is of the Shat-noir but the method is the
same.
USE
Spasm needs a signal on the CV Freq input to react to. I usually prefer gates
but anything will do.
The feedback pot controls the size of the jerk, the change will not always be
obvious but it depends on the frequency and patch you have.
This pic shows the Feedback pot at minimum, yellow trace is output 1, blue
trace is output 4. Tri from LFO is patched to the CV Freq input. It can be
seen the reset jerks are very large, up to +/-10V.
Same details as above but Feedback pot at maximum. The reset jerks are much
smaller, generally under 5V, tho the odd 10 volter still happens………this is
chaos not tea and scones on the lawn.
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