+10V
-10V
0V
+5V
(+/-5V signal, full +saturation)
(+/-10V signal, full +saturation)
(+/-10V signal, - VC+saturation)
FULL SATURATION WAVEFORMS - POSITIVE ONLY
The graph to the right illustrates the effect of the saturater at the lowest
clipping level. Only the positive saturater is shown as the purpose is
simply to illustrate the effect of the saturation circuitry. The first half of
the wave cycle for each example is the unaffected triangle wave. The
second half is the positive only saturated waveform. Three examples are
shown to describe the effect of saturating higher amplitude signals and
how the saturater works while under the influence of voltage control via
the MIXMODE Expander.
Example
a.
and
b.
are both produced using the PCB trimmers or the panel
The SCIENCE of the MIXMODE SATURATER
MIXMODE features a unique saturation circuit. Saturation and distortion are useful tools for additive synthesis. The simplest way to add distortion to a signal is to amplify it enough to exceed the input level of active devices such as
transistors and operational amplifiers. While transistors and other discrete semiconductors produce a natural soft saturation when overdriven, op amps will often clip rather abruptly. This is known as hard clipping and can be very
useful for adding serious distortion and wave shaping into square-ish waveforms. Without getting too technical, it should be mentioned that the square wave can be constructed by summing all the odd order harmonic frequencies. In
other words a series of sine waves beginning at the fundamental, combined with every other harmonic at specified amplitudes will eventually produce the square wave shape. For more details on this amazing phenomenon, study the
Fourier series expansion of periodic functions. In fact, given that the sine is a pure tone, all known waveforms can be decomposed into a series or sum of sine waves - these are the harmonics or overtones we hear in sound. By extension
of this phenomenon, clipping distortion adds harmonic content the further and harder a signal is driven into clipping - thereby producing a near square like function. But the function is never really a square so a variety of overtones,
odd and even are heard in different amounts when we distort different waveforms. Composing a series of even ordered sines will result in asymmetric waveforms. Therefore, we can accentuate the even harmonic content of a signal
with asymmetrical distortion. We can accomplish this by simply choosing to only clip the negative half of the waveform for instance. The order of the harmonic content is directly related to the tonal qualities of the sound. Odd
harmonics are found in bell tones and generally an-harmonic sounds like metal bangs and clangs and heavy metal guitar chords. The even harmonics are very sweet and musical, very melodic. So by arbitrarily clipping signals both
symmetrically and asymmetrically, we can control the level of harmonic content we would like to add to a sound. While hard clipping is a very easy way to add harmonic content, sometimes it can produce too many overtones too
quickly to provide a wide variety. A soft clipper is known to be more musical because the signal will not flatten out so abruptly. This produces less overall harmonic content and allows the even ordered tones to be more audible. This is
why tube distortion and germanium clipping are known as sounding sweet, rich and musical. This is also where MIXMODE’s saturation circuitry excels. The saturater exhibits a mix between the very soft saturation of a transistor at
higher clipping levels then into a soft diode clipping and into harder clipping when driven much further at the lowest threshold levels. Additionally, MIXMODE’s saturater tends to leave some of the original peak content intact but
compressed. All this allows for a wider range and variety of harmonic content to be revealed. The results are more useful than traditional clipping distortion. The independent control over the positive and negative threshold level adds
even more tonal variety. In fact MIXMODE's saturater is so deep that the effect is similar but in some cases richer than phase shifting as the threshold is modulated. The saturater works like an anti-filter; adding harmonics rather than
removing them!
See the graph below for an example of what MIXMODE’s saturation looks like when applied to a triangle wave. Only the positive half of the triangle wave is saturated for clarity.
a.
b.
c.
controls of the MIXMODE Expander. Example
c.
Illustrates the effect of voltage controlled saturation. The modulation behavior for the positive (+)saturater works like the PCB/panel controls starting from a 10V CV level down to about 0V.
The CV will continue to clip the positive peak below 0V but will squeeze and offset into the negative half with the applied negative CV levels. The graph
c.
highlights this effect. Offset is not shown for clarity. This behavior is mimicked by
the negative CV input but for opposing CV levels. As a result, a greater range of tones and effects are possible when control voltages are used to modulate the saturater.
ADJUSTING THE SATURATER
If you would like to change the saturation setting to your preference without the MIXMODE Expander, the adjustments are very easy to perform. On the back of MIXMODE you will notice the two large blue trim pots with a grey Phillips
head center. Simply use a small Phillips or Flat head screwdriver to rotate the trim pot to your desired threshold level. Fully counter clockwise is approximately 10V and fully clockwise is about 3.8V. You can perform this adjustment
while the unit is powered and a signal is present and monitored at the mixer output. The top trimmer adjusts the positive, and the bottom trimmer the negative signal excursions.
CONNECTING THE EXPANDER
The MIXMODE Expander adds a whole new dimension to the saturation possibilities and adds dedicated mixer outputs.
Connecting the Expander is straight forward. Remove the four jumpers from the expansion header on the back of MIXMODE. Put them aside in a safe place. Locate the expansion cable that came with your Expander module. Note the
RED stripe on the expansion cable. Attach the expansion cable to the Expander with the RED stripe facing down towards the bottom of the module. Take the other end of the cable and attach it to the expansion header on MIXMODE
with the RED stripe facing down - towards the bottom of MIXMODE. Now with the back of both modules facing you and oriented in the same direction, the RED stripe should be facing the same direction on both modules. If they are,
you are almost done. The last step is to turn both saturation trimmers all the way clockwise. When completed, you are ready to connect power as directed above and use the expander with MIXMODE!
BEFORE YOU BEGIN - CONNECTING POWER
Before using MIXMODE, you must first connect the power cable correctly. Locate the small connector end of the power cable and take note of the RED stripe on the cable. Connect the small end of the cable to the power header on
MIXMODE with the RED stripe down towards the bottom of the module. Double check that this is the case before installing and powering up your module. Connect the other end to your power bus-board with the RED stripe aligned
with the -12V (negative 12 VOLTS) rail marking. MIXMODE is reverse polarity protected so mistakes will be forgiven however it is good practice to always take special care when connecting power to Eurorack devices. Some are not so
forgiving!
Please be sure not to confuse the expansion header marked ‘expansion’ for the power header which is marked ‘power’. The expansion header also contains four jumpers. Do not remove these unless you are connecting the Expander as
described below.
WARRANTY/GUARANTEE
MIXMODE is covered for defects and malfunctions for one year after purchase. However we are happy to help you out with any problems beyond this time-frame. As with all SSF designs, we will take good care of you!
Please be kind to your modules and do not abuse them. Treat them with love and respect and they will return that love many orders of magnitude greater for a lifetime. Enjoy! <3
CHANNEL OUTPUT JUMPER OPTIONS
Jumpers selectors are provided for channels 1-3. These two pronged jumper selectors are shipped with the option to select each channel to be removed from the mix when a patch cable is inserted to the respective output jack. If you
wish to change this behavior on one or more channels, simply remove the jumper or move the jumper over so that only one prong is connected to the jumper. This way the jumper stays in one place and can be easily switched back on if
desired. Can’t decide which option is best for your needs? Here are some reasons to help you decide. For choosing to leave a signal in the mix, this will allow you to mix a signal and separately patch the signal out to another destination
while the attenuator controls the output level and the level in the mix. This is great for combining CVs while patching them individually out.
Selecting to remove the signal from the mix will allow you to create small mixes and use the attenuators separately. This is useful is a small system or if more than one function is needed at a time. You could also use one channel as a
master volume control for a mix of three or less channels.
