Din Sync VCF303 User manual

Dear customer,
Thank you for your purchase of the VCF303 eurorack filter module.
The VCF303 is a clone of the Roland TB-303 filter which also includes the envelope generator
and accent circuit of the TB-303 in order to get an authentic sound. It also features CV control
over the cutoff frequency and an overdrive knob for driving the input section.
While I’m sure many of you will be using this to make “acid” style sounds, don’t forget to explore
using it as a source of other patch types. I’m sure you’ll be pleasantly surprised with the results.
Please take your time to read the installation instructions and to try out the patch examples.
Your module comes with 12 months free technical support for the original purchaser, just drop
an email to [email protected] if you have any questions or problems.
Again thank you for your purchase, it’s much appreciated. And don’t forget to keep an eye on
http://www.dinsync.info for the forthcoming OSC303MKII which will appear sometime in the very
near future.
Paul
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Who reads manuals anyway?
I know right? but please at least read the installation and quick start.
Installation
The VCF303 has reverse power protection, so plugging the power cable in backwards should
result in no damage to the module itself. However plugging things in backwards is never a
good idea and could potentially damage other parts of your system. The protection is there in
case of plugging the power cable in backwards by accident, please still take care to check the
orientation of the cable when connecting it for the first time.
figure 1 - the correct and wrong way to connect power
Before installing please power off your modular case. Connect one end of the cable to the
module as shown in figure 1. Connect the other end of the cable to your modular case bus
board, please check your case’s manual for the correct orientation. The stripe on the cable
should be connected to -12. After you have connected the power you can mount the module
using the included screws, the VCF303 requires 12HP of cabinet space.
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Quick Start
While standard usage is pretty straight forward, please first set the overdrive and volume levels
to zero. The reason for doing this is that the output with full overdrive and maximum volume is
capable of very high levels which could cause clipping to anything after the module in the signal
chain.
Next connect the signal to be filtered to the INPUT jack and connect the OUTPUT to your mixer
or vca. Connect a clock input to ENV TRIG and/or AC-TRIG.
Turn the volume to about halfway and adjust the other controls (except overdrive) to taste. You
should now be hearing that familiar rubbery liquid filter sound.
To get the most from your VCF303 please read the following sections which describe the
feature set and their interactions with each other in more detail.
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Filter Section
The CUT OFF FREQ knob adjusts the cutoff point of
the filter. Turning the knob to the right allows more high
frequency content to pass, resulting in brighter timbres.
Turning the knob to the left closes the filter and less high
frequency content is passed, resulting in duller timbres.
As on the original TB-303 it is not possible to close the
filter completely from the knob alone.
The CV input jack allows voltage control of the cutoff
frequency. Use this jack with LFO’s or audio rate
modulations. If you use an offset generator with this input
you will be able to take the cutoff frequency beyond that
of the TB-303. This will enable you to close the filter
completely, or open it more than the standard range.
This jack is not attenuated, so in some cases, ie with an
LFO it may be necessary to attenuate the signal before it
reaches this input jack.
When the RESONANCE knob is turned up harmonics at
the cutoff frequency are boosted.
As more resonance is added the overall timbre becomes
thinner and more “acidic”.
With little or no resonance the overall timbre becomes
thicker and more chunky. Try some no resonance
basslines with an OSC303 for some lush bouncy tones.
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Envelope Section
The ENV MOD knob controls the amount of signal from
the envelope generator that reaches the CUTOFF circuit.
As with the TB-303 it is not possible to completely turn
off the envelope modulation.
If this knob is adjusted without an envelope being
triggered it will provide an offset for the cutoff frequency.
The DECAY knob controls the length of the decay of the
envelope.
Due to the way the ACCENT circuit works, this knob will
have no effect at all while an accent trigger is held. This
is one of the quirks that give the TB-303 its signature
sound.
Use the ENV TRIG jack to control when the envelope
fires. For standard 16th note TB-303 style sequences
this jack will work best when driven from a constant 16
pulse clock signal.
ie: a new envelope triggered for every new note played.
The envelope can be tapped at the OUT jack for other
purposes, and the module could be used as a simple
envelope generator.
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NOTE: The front panel LED shows the envelope activity.
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Accent Section
The AC TRIG jack controls when an accent is fired. The
accent works best when timed in conjunction with the
envelope generator. When accents are triggered, the
envelope decay is cut short (ie the decay pot no longer
works).
To best understand the relationship between the accent
and the envelope it’s better to think of the accent
trigger as controlling an internal switch which allows the
shortened envelope to enter the resonance circuit.
While the accent jack is high, the ENV DECAY knob will
not have any effect.
Using short triggers on the AC TRIG will not work as well
as timed gates. See figure 2 for a description of how
best to trigger this jack for standard basslines.
The AC TRIG jack is normalled to the ENV TRIG jack so
that when nothing is plugged into the ENV TRIG jack,
sending a pulse to the AC TRIG will trigger both the
envelope generator and the accent circuit.
The OUT jack can be sent to an external vca to achieve
the typical TB-303 volume increase associated with
accents.
The ACCENT knob controls the amount of the shortened
envelope that reaches the resonance circuit and the
accent OUT jack.
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NOTE: The accent output jack may need attenuation or boosting depending on the vca used.
If you have a vca with only one input you can use a dc coupled mixer to combine your accent
output with your adsr before it reaches the vca.
See the patch sections for an example of how to set this up.
Of course you don’t need to use the accent out on a vca, you'll still get an accent sound but
not the volume increase.
figure 2
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Input and Output Sections
Connect the signal to be filtered to the INPUT jack. This
works best with standard eurorack oscillators but will
also work on any normal audio signal.
The OVERDRIVE knob overdrives the filter input. The
initial 40%-50% of its turn may be subtle depending on
the level of the signal connected to the INPUT jack.
Once the overdrive starts to bite, the resonance is
suppressed and the overall tone will have a more
compressed sound.
TIP: a small amount of overdrive will lower the volume
decrease associated with increased resonance levels on
the TB-303
The VOLUME knob controls the overall output.
The VCF303 has a fixed output level and this knob is
simply an attenuator.
NOTE: With a strong signal at the filter input, and with
OVERDRIVE/VOLUME at maximum the VCF303 is
capable of very high levels (up to around 20v peak to
peak)
Be sure to lower the volume level in these cases to
avoid clipping to anything in the signal chain after
the VCF303.
The OUTPUT jack carries the filtered signal, connect this
to a vca or mixer.
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Patch Examples
Basic Acid Patch
additional modules needed, OSC303 (or other oscillator), Sequencer, ADSR, VCA, Clock
source.
Connect Sequencer cv out to OSC303 cv in
Connect OSC303 square or saw output to VCF303 input
Connect VCF303 output to vca signal in
Mult clock pulse to VCF303 ENV TRIG, Sequencer clock in and ADSR trigger in
Connect ADSR output to vca cv in
Advanced Acid Patch
additional modules needed, OSC303 (or other oscillator), Makenoise, Rene, Brains+Pressure
points (or equivalents), ADSR, VCA with two cv inputs or VCA with one cv input and a DC
coupled mixer, attenuator or gain amplifier (optional), Clock source.
Connect Rene QCV to OSC303 cv in
Set Rene to snake mode (X FUN page)
Set Rene glide on (X FUN PAGE)
Connect Pressure Points top row output to Rene XMOD
Connect Pressure Points second row output to VCF303 AC TRIG
Optionally connect Pressure Points bottom row output to VCF303 CV (if you want sequenced
cutoff)
Connect OSC303 square or saw output to VCF303 input
Connect VCF303 output to vca signal in
Mult clock pulse to VCF303 ENV TRIG in, Rene XCLK, Brains clock in and ADSR trigger in
Connect ADSR output to vca cv in 1 (if you only have a single cv input on your VCA then
connect ADSR output to DC coupled mixer in and connect mixer output to vca cv in)
Connect VCF303 ACcent out to vca cv in 2 (if you only have a single cv input on your VCA then
connect VCF303 ACcent output to DC coupled mixer in)
Depending on the sensitivity of your vca you may wish to place an attenuator or gain amplifier
between the VCF303 ACcent out and vca.
Use the top row of Pressure Points to control sequencer glides
Use the middle row of Pressure Points to control accents
Use the bottom row of Pressure Points to control frequency cutoff (if connected)

VCF303 as Envelope Generator
Connect trigger to VCF303 ENV TRIG
Take envelope from ENV out
The decay knob will control the length of the envelope.
Cross Modulation
Using either the Basic or Advanced Acid patch, connect the unused OSC303 output to the
VCF303 CV input.
Extended Cutoff Range
Additional modules needed, Manhattan Analog CVP (or equivalent offset generator)
The VCF303 range is limited to the same as the TB-303. In other words it is not possible to
completely close the filter. If you want to get an extended Cutoff range connect the CVP output
to the VCF303 CV in.
Set VCF303 cutoff knob to 100%
Set CVP glide to 0%
Set CVP level to 50%
Use CVP offset to control cutoff frequency, you will now find you will be able to close the filter
completely and open it beyond the standard range.

Adjustment Procedure
Please read all of this section before attempting to adjust the modules internal trimmers, failure
to do so may kill many tiny animals but could also potentially kill your module.
This section is intended for those with the necessary skills and experience with calibration
adjustments. It is provided as a complimentary supplement and should not be attempted
unless you fully understand what’s involved. If you misadjust your module it may become quite
unusable.
In order to correctly adjust your module you will need a digital volt meter and an oscilloscope.
The module has been adjusted and calibrated before shipping, however like all analog devices it
may need adjustment in the future or after being in transit.
figure 3 - location of trimmers and test points

Adjusting the reference voltage
The module creates it own reference voltage internally, this needs to be 5.33v.
1: First power up the module and allow to warm up for a few minutes at room temperature.
2: Get a digital volt meter and connect the red probe to TP1 and the black probe to TP2.
3: The meter should read around 5.33v, if it does then you can skip the rest of this section. If not
then carefully adjust TM1 until you read 5.33v (or as close as you can get)
4: *WARNING* The trimmer is quite sensitive and it is possible to dial in over 10v so
gently does it, we aren’t responsible if you decide to cook your module with more than the
recommended amount of 5.33v.
Adjusting the cutoff center frequency
To adjust the center frequency of the cutoff. First turn all front panel controls to 0% and set
cutoff to 50%, resonance to 100% and volume to 50%.
Connect a saw waveform (preferably an OSC303) tuned to 110hz to VCF303 INPUT
Connect a trigger to ENV TRIG
Connect an oscilloscope to VCF303 OUTPUT
While triggering the envelope adjust TM3 to read between 1.8 and 2.0 ms on the first pair of
resonant peaks. See figure 4.
figure 4

Acknowledgements
many thanks go out to
Stephen Kwartler from http://www.pro-modular.com for the panel design.
Chris “Infradead” Lehfeldt for beta testing.
Additional thanks to Tony at Makenoise and Jason at Manhattan Analog for their permission to
use their module names in the patch section of this manual.
Specifications
Size: 12 HP
Depth: 38 mm (depth is measured from the rear of the faceplate to the edge of the supplied and
connected power cable)
Power consumption: 20 mA (<20mA +12, <5mA -12)