flight of harmony
Eurorack Module
~rev1.0~
Components
1
Assembled Sound of Shadows digital delay module
1
DC power cable – 9” Ribbon cable (Doepfer standard)
4
M3x0.5x5mm Stainless-Steel machine screws
4
M3 Nylon washers
Specications
Supply Voltage
Supply Current (max draw @ ±12V)
Max. Input Voltage (@ ±12V)
Max. Output Voltage
Input & Ouput (I/O) coupling Direct*
Output Impedance 1kΩ
Control Voltage (CV) inputs
CV input coupling Direct
CV input impedance
* I/O jacks are direct-coupled. The Delay circuit itself is not. A DC signal at the input will be
available at the Clean, Mix, and VCA outputs, but not available at the delay output.
IV+= 51mA IV-= -21mA
±12VDC
10V
p-p
6V
p-p
±V
supply
100kΩ
1/8
What is it?
DELAY
In Out
Input
x -1
x -1
In Out
FEEDBACK
Clean
out
Mix
out
Mix
Delay
out
Insert
jack
EXT
VCA
out
In Out
VCA
VCAIN
jack
EXT
Sound of Shadows flowchart
The Sound of Shadows (SoS) is a voltage-controlled (VC) digital delay
module based around the PT2399 echo IC1 from Princeton Technology – which
was, by the way, originally designed for Karaoke equipment. The SoS is essentially
two separate modules: a delay and a voltage-controlled amplier (VCA). The
focus of the SoS was the delay while the VCA was thrown in because half of an
LM13700 IC was unused, so the VCA is very basic.
As with all f(h) products, the SoS was engineered towards maximizing
functionality while keeping cost as low as possible. If some aspects of the unit
seem awkward, it is most likely due to this. The goal is to make unique, useful,
enjoyable, and affordable instruments, not just hoover2 out your bank account.
And remember: every instrument has its quirks and unexpected aspects,
so RTFM3! All the way through! Specic quirks are mentioned in the description of
the particular feature they apply to, so please read this through before emailing!
Feature summary:
Delay
VC delay rate•
VC feedback level•
Signal input•
Input breakjack•
CV input•
Output•
Clean, Delayed, and Mix •
outputs
Feedback loop insert jack•
The 30-pin header on the back of the module is for the SoS expansion
module, currently in development.
1) Integrated Circuit
2) Hoover is a company that manufactures vacuum cleaners.
3) RTFM = Read The F*cking Manual!
2/8
VCA
Controls
Rate: This controls the delay clock rate, which in turn controls how fast the
delay steps through its memory array and thusly the amount of delay. Clockwise
rotation increases the rate (which decreases the delay time), counter-clockwise
decreases the rate (which increases the delay time).
Feedback: Controls how much of the delayed signal is fed back into the
delay cell. Feedback is what creates a reverberation or echo sound – multiple
repetitions of an acoustic event. Clockwise rotation increases the amount fed
back, and thus the number of repeats, counter-clockwise decreases the amount.
The nominal operating area is between 6:00 and 9:00 during normal
usage. More than this will set up a self-propagating feedback cycle that will
quickly get out of hand.
Insert: This is the attenuator for the feedback loop insert jack. The
jack is situated between the delay cell output and the feedback cell input.
The feedback cell input is calibrated for the output of the delay cell, which
is around 1.5V
overload the feedback cell unless attenuated, hence the Insert attenuator.
Turn clockwise to increase the signal level, counter-clockwise to attenuate.
When not using the Insert jack, it is recommended to keep this control
turned fully clockwise, to the maximum position. Otherwise, you are attenuating
the output of the delay cell, which will affect everything else further down the
signal path.
Input: This is the input level control. Just like a volume knob – clockwise
increases level, counter-clockwise attenuates the signal level.
Mix: Um, yeah. Guess what this controls? The balance of the mixed signal
at the Mix output! Seriously, this controls the mix between the Clean and Delay
signals at the Mix jack, really!
VCA: This controls the VCA output level – A.K.A.4: the volume knob.
Standard behavior with a minor quirk – this control will not fully attenuate the
output, but a negative CV applied to the VCA CV input will bring the level much
further down. It was either this or add another IC + associated components to the
PCB and jack the price further up.
maximum, and most standard signals inserted here will
p-p
4) A.K.A. = Also Known As
3/8
Jacks
g.1
type and direction (into or out of the
module) of the relevant signal. The
VCA jacks are just labeled “VCA”,
as the function of each is already
described by what row they are in.
The jacks are grouped by the
CV in
Rate: Quirk warning: Rate
CV behavior is inverted. Negative
increases rate, positive decreases. If
that bugs you too much, just think of it as the delay CV input and the issue
magically disappears! Positive increases the delay, and negative decreases
the delay.
Feedback: This works normally, positive CV increases feedback, negative
decreases same.
VCA: Same as feedback, positive CV increases the output level, negative
attenuates it.
Signal in
Input: This is kind of important for a delay unit: you need a signal to delay,
or else they’re somewhat dull effects. This is the jack where that signal is input
into the delay.
Insert: This is the feedback loop insert breakjack. Inserting a plug here
will disconnect the output of the delay cell from the input of the feedback
cell, with the inserted signal now going directly to the feedback gain cell.
One use for this is to insert an effect – or even another delay unit (yes,
they can be daisy-chained quite effectively) – into the feedback loop. To do this,
patch the Delay out into the desired effect, and the output of the effect into the
Insert jack. You may need to adjust the Insert level control (see above) for best
sound.
VCA: This is another breakjack. The input of the VCA is normalized
(normally connected to) the Mix output. Inserting a jack here breaks that
connection, enabling the VCA to be used completely independently of the rest
of the module.
Output
Clean: A buffered and inverted copy of the input signal.
Delay: The buffered & scaled output of the delay cell
Mix: A linear mix of the Clean and Delay signals, the balance of which
is set by the Mix control pot.
VCA: Output of the VCA.
4/8
Other connections
+
-
1
PWR-E
PWR-F
GND
GND
CLKOUT
CLNDELMIX
FBCV
IN
(
R
)
IN
INVCLN
MIXVCA
MIXOUT
RTCV
(
R
)
RTCV
RTPTWPR
SPARE2
SPARE3
CLNMIX
DELFB
DELMIX
DELOUT
FBCV
FBIN
FBWPR
(
R
)
RTEPT3
V+
V-
VCACV
(
R
)
VCACV
VCVACV
VCAIN
VCAOUT
Power: The power connector header is
a 2x5 shrouded box header which
accepts the standard Doepfer power
cable. This header style is polarized,
meaning the connector can only be
inserted one way, to prevent connecting
the power backwards and damaging
the unit.
This assumes that you are using either
the supplied cable or one manufactured
by Doepfer.
Looking at the rear of the module, the
negative supply (red stripe) is on the
left, positive supply is on the right (see
g.2).
Expansion Header: This is provided
for an upcoming expansion module
which contains a number of functions
g.2
that were considered “extras” – that is,
beyond those required for basic usage
– but feel free to make use of them for
your own DIY5 needs. However, if you
do so, you do this AT YOUR OWN RISK. We will not be held liable for damage
caused by misuse of this module.
Pins marked with “(R)” are signal inputs that are ready for use with no
additional components. Some are already utilized via jacks on the panel (denoted
with “(J)” in the description), however, and no provision has been made for proper
mixing of additional inputs – which means that they should be considered as a
“multiple” if used. The “(R)” means that they are connected to a summing resistor
on the input of an opamp on the main PCB.
Pins of the same name but without the “(R)” are connected to the same
opamp input as the one with the “(R)”, but do not have a summing resistor, you must
supply one. All f(h) summing inputs are standardized with 100k input resistors.
This was done to allow the user to add as many inputs as desired (within reason
of course), but all from one pin.
All outputs have 1k protection/impedance resistors.
Unless marked as described above, assume the terminal is NOT
protected.
“con.” = connection.
5) DIY = Do It Yourself
5/8
GND
GND
CLKOUT
CLNDELMIX
FBCV
IN
(
R
)
IN
INVCLN
MIXVCA
MIXOUT
RTCV
(
R
)
RTCV
RTPTWPR
SPARE2
SPARE3
CLNMIX
DELFB
DELMIX
DELOUT
FBCV
FBIN
FBWPR
(
R
)
RTEPT3
V+
V-
VCACV
(
R
)
VCACV
VCVACV
VCAIN
VCAOUT
The descriptions will be minimal, if they aren’t enough for you, you should
not be messing with them.
Top row, left to right: Bottom row, left to right:
IN(R) Signal input (J)
IN Signal input
MIXOUT Mix signal out
MIXVCA con. Mix buffer VCA in
CLNDELMIX Wiper of mix pot mix
buffer(R)
INVCLN Clean signal out (J)
SPARE3 nothing
GND Ground
SPARE2 nothing
GND Ground
CLKOUT Delay IC clock out
RTPTWPR Wiper of rate pot
RTCV Rate CV input
RTCV(R) Rate CV input (J)
FBCV Feedback CV input (R)
CLNMIX con. Clean buffer mix pot
DELOUT Delay signal out (J)
DELMIX con. Delay buffer mix pot
DELFB
con. Delay IC out insert
breakjack
VCAOUT VCA output (R)
V+ Supply V+ (+12V)
VCAIN VCA input (R)
FBIN
VCVACV
con. Delay IC out feedback cell
input (R)
(typo, sorry) v.ref. for VCA CV pot
minimum
V- Supply V- (-12V)
VCACV VCA CV input (J)
VCACV(R) VCA CV input
RTEPT3 v. ref. for rate control minimum
FBCV Feedback CV input
FBWPR(R)
con. Feedback wiper FB level
buffer
6/8
Stuff
Muffwiggler forums, come check it out! People have posted some excellent
demos on there. I haunt the forums as well, and new things are posted there
long before they hit the f(h) website.
A big thank you to those who have sent in suggestions and comments,
keep them coming!
Send samples to: samples@ightofharmony.com
Comments, suggestions, complaints to: ight@ightofharmony.com
Drawings and designs ©2010 ight of harmony / Red Hand Studios
There is a lot of discussion about the Sound of Shadows on the
http://www.muffwiggler.com/forum/index.php
http://www.ightofharmony.com
Revised Feb, 2010.
We are tomorrow’s shadows...
7/8
f(h)
8/8
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