XAOC 1964 Stereo VC Frequency Shifter Module Instruction Manual
- June 12, 2024
- Xaoc
Table of Contents
XAOC 1964 Stereo VC Frequency Shifter Module Instruction Manual
Module Explained
SALUT
Thank you for purchasing this Xaoc Devices product. Koszalin [kɔˈʃalin] is a
stereo frequency shifter (2 ins/4 outs) offering both quasi-exponential and
linear frequency modulation as well as full stereo feedback under voltage
control. Frequency shifting results in a linear translation of the signal
spectrum, which produces a variety of atonal sounds. It should not be confused
with frequency scaling, also known as pitch shifting. Complex phase
cancellation patterns occurring with frequency shifting and deep feedback
produce spectacular barber-pole effects.
Koszalin offers direct controls over feedback amount, feedback routing, and
feedback response.
It also facilitates frequency modulation of any stereo audio signal, thanks to
the linear TZFM input. Koszalin is a digital module with a DSP behind an
analog interface.
INSTALLATION
The module requires 10hp worth of free space in the Eurorack cabinet. Always
turn the power off before plugging the module into the bus board using the
supplied 16-pin/16- pin ribbon cable, paying close attention to power cable
pinout and orientation. The red stripe indicates the negative rail and should
match the –12v mark on the bus board and the unit. Koszalin is internally
secured against reversed power connection; however, flipping the 16-pin header
may cause serious damage to other components of your system because it will
short circuit the +12V and +5V power lines. Always pay particularly close
attention to the proper orientation of your ribbon cable on both sides!
The module should be fastened by mounting the supplied screws before powering up. To better understand the device and avoid common pitfalls, we strongly advise the user to read through the entire manual before use.
MODULE OVERVIEW
Front panel overview
Frequency shifting
Havior in the “Negative Frequencies?” section).
The functions of these two pairs effectively swap when the shift knob is
turned to the left of 0Hz, or a negative control voltage is applied.
WHAT IS FREQUENCY SHIFTING?
Frequency shifting is a process that affects all spectral components of a
signal by changing their frequencies by an equal number of Hz.
For example: if the input is a periodic waveform with a 1kHz frequency, it usually contains the 1kHz component plus the harmonic overtones: 2kHz, 3kHz, 4kHz, etc. When this signal is shifted by 200Hz the result contains 1.2kHz, 2.2kHz, 3.2kHz, 4.2kHz, etc. (fig. 2).
That means the new components are no longer multiples of the first frequency; hence the signal is inharmonic and non-periodic.
Bear in mind that this is a very different effect to pitch shifting, which results in scaling the frequencies by the same factor. So, for example, applying a factor of 1.2 would result in a signal that contains 1.2kHz, 2.4kHz, 3.6kHz, 4.8kHz, etc.—still a harmonic signal, just with a different pitch.
Technically, shifting of the spectrum is achieved through Single Side Band (SSB) modulation that is much more complex than a simple multiplication, which is sometimes inappropriately called ring modulation.
A common fallacy says modulation is the same as adding and subtracting signals, which is nonsense since multiplying is not adding and subtracting. Instead, this type of modulation (specifically, four quadrant amplitude modulation) affects individual harmonic components in such a way that their frequencies are added and subtracted.
The SSB separates these modulation products and offers two new signals: one with frequencies shifted up and one with frequencies shifted down. This is obtained by complex filtering, phase rotation, and quadrature modulations, which are difficult to achieve with analog technology but relatively easy with DSP. note: summing both down- and upshifted signals reduces the effect to a mere multiplication (balanced modulation, aka “ring mod”).
Negative frequencies
NEGATIVE FREQUENCIES?
Consider a point rotating on a circle at X rpm. When observed along one
dimension, it would oscillate sinusoidally with a frequency of X/60 Hz
(because there are 60 seconds in a minute). If we slow down the circle, the
frequency decreases towards 0Hz, but when we stop the circle and change the
direction, the frequency starts rising again—towards the negative frequency
values.
Sinusoids with negative frequencies are indistinguishable from those with positive frequencies, except when crossing zero. This zero-crossing is why through-zero frequency
Effects of feedback
fig. 4: time-frequency response of frequency shifting with feedback
Modulation sounds different than positive-only FM. Frequency shifting by increasing negative amounts has a distinctive effect that at some point, the original frequencies approach zero, cross it, and then start to increase again (see fig. 3). For example, with the incoming signal frequency being 300Hz, turning the shift knob counterclockwise to the -300Hz position, i.e., 30 with the x10 switch engaged (while listening to the up shifted outs), compensates the original frequency, so the result reaches 0Hz (300-300=0). Beyond this point, as we hear it, the frequency appears to be increasing, even though it actually moves towards -inf.
Interestingly, shifting a harmonic signal down moves its fundamental to an inaudible DC. At the same time, all the overtones move down by one position, thus producing a harmonic signal again. Further shifting, however, causes its fundamental to appear in increasing (negative) frequency, as opposed to its other components, which still decrease toward zero; thus, the signal becomes increasingly inharmonic.
THE EFFECTS OF FEEDBACK
Feeding a frequency-shifted signal back to the input of the shifter creates a
cascade of shifts because part of the signal is shifted multiple times. If the
shift is slight, a comb response
is created resembling a very deep, resonant flanger. Phase cancellation
creates ripples that move in time and frequency (fig. 4), yielding a
spectacular barber-pole effect. Koszalin offers two controls of this behavior
through its regen and density knobs and CV inputs.
Additionally, three feedback configurations are available via the regen switch. The left and middle positions select feedback created from the downshifted and upshifted stereo pair of outputs, respectively. Finally, the rightmost position selects combi with the left channel from the down shifted out and the right channel from the up shifted out. The combined feedback position is useful when patching both stereo channels in series (see: “Patch ideas”).
SOUND QUALITY CONSIDERATIONS
Koszalin is designed to operate on audio signals with Eurorack levels;
therefore, a ±5V input is recommended. For best audio quality, avoid using
very quiet signals and amplifying the output to compensate. Conversely, avoid
overdriving the input with very hot signals— use the color input indicator LED
as a general guide for optimal signal level. Due to internal gain staging,
there is a chance of amplifying noise from the bus board; hence, the quality
of power supply and distribution impact the output signal. We recommend using
linear, and to a lesser extent, hybrid (switching converters followed by
linear regulators) power solutions since they are quieter than switching-type
power regulators. Additionally, we suggest
avoiding “flying bus” cables as they increase coupling between modules which
can cause interference and instability.
PATCH IDEAS
• Feed a sinusoidal signal from your oscillator to the left or right input of Koszalin. Set the shift knob to zero and set regen to zero.
Patch another audio rate signal to the lin tz fm input (directly or through a VCA) and set the small attenuator to taste—now you have an FM operator. You can replace the input sinusoid with any other signal, e.g., from a sampler, to get a different flavor of FM. note: the result of modulation will smear and diminish when you add feedback.
• Take any plain signal to Koszalin’s right input, take the right up shifted out and patch to the left input, then listen from the left down shifted out. These two shifts will cancel, but the interesting part is what happens in- between. Set the regen switch to combi and turn the regen knob up. Manipulate the amount of shift and density for different effects. This creates a kind of filter with an extraordinary response. Try pinging it. You can also flip the shift direction for a different effect.
ACCESSORY
Our Coal Mine black panels are available for all of Xaoc Devices modules. Sold
separately. Ask your favorite retailer. •
WARRANTY TERMS
XAOC DEVICES WARRANTS THIS PRODUCT TO BE FREE OF DEFECTS IN MATERIALS OR WORKMANSHIP AND TO CONFORM WITH THE SPECIFICATIONS AT THE TIME OF SHIPMENT FOR ONE YEAR FROM THE DATE OF PURCHASE. DURING THAT PERIOD, ANY MALFUNCTIONING OR DAMAGED UNITS WILL BE REPAIRED, SERVICED, AND CALIBRATED ON A RETURN-TO- FACTORY BASIS. THIS WARRANTY DOES NOT COVER ANY PROBLEMS RESULTING FROM DAMAGES DURING SHIPPING, INCORRECT INSTALLATION OR POWER SUPPLY, IMPROPER WORKING ENVIRONMENT, ABUSIVE TREATMENT, OR ANY OTHER OBVIOUS USER-INFLICTED FAULT.
LEGACY SUPPORT
IF SOMETHING GOES WRONG WITH A XAOC PRODUCT AFTER THE WARRANTY PERIOD IS OVER,
THERE IS NO NEED TO WORRY, AS WE’RE STILL HAPPY TO HELP! THIS APPLIES TO ANY
DEVICE, WHEREVER AND WHENEVER ORIGINALLY ACQUIRED. HOWEVER, IN SPECIFIC CASES,
WE RESERVE THE RIGHT TO CHARGE FOR LABOR, PARTS, AND TRANSIT EXPENSES WHERE
APPLICABLE.
RETURN POLICY
THE DEVICE INTENDED FOR REPAIR OR REPLACEMENT UNDER WARRANTY NEEDS TO BE
SHIPPED IN THE ORIGINAL PACKAGING ONLY AND MUST INCLUDE A COMPLETED RMA FORM.
XAOC DEVICES CAN NOT TAKE ANY RESPONSIBILITY FOR DAMAGES CAUSED DURING
TRANSPORT. SO BEFORE SENDING US ANYTHING, PLEASE CONTACT US AT
SUPPORT@XAOCDEVICES.COM. NOTE THAT ANY UNSOLICITED PARCEL WILL BE REJECTED AND
RETURNED!
GENERAL INQUIRIES
FOR USER FEEDBACK SUGGESTIONS, DISTRIBUTION TERMS, AND JOB POSITIONS, FEEL
FREE TO CONTACT XAOC DEVICES AT INFO@XAOCDEVICES.COM. PLEASE VISIT
XAOCDEVICES.COM FOR INFORMATION ABOUT THE CURRENT PRODUCT LINE, USER MANUALS,
FIRMWARE UPDATES, TUTORIALS, AND MERCHANDISE.
ALL RIGHTS RESERVED. CONTENT COPYRIGHT ©2022 XAOC DEVICES. COPYING, DISTRIBUTION OR ANY COMMERCIAL USE IN ANY WAY IS STRICTLY PROHIBITED AND REQUIRES THE WRITTEN PERMISSION BY XAOC DEVICES. SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT PRIOR NOTICE. EDITING BY BRYAN NOLL.
MAIN FEATURES
Full stereo frequency shifting with 2 inputs and 4 outputs 3 ranges of shift: 50Hz, 500Hz, and 5kHz Independent exponential and linear thru-zero control inputs Internal feedback under voltage control.
TECHNICAL DETAILS
Eurorack synth compatible 10hp, skiff friendly Current draw: +140mA/-30mA Reverse power protection
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