METASONIX RK8 Filterwall User manual
RK8 Filterwall
owner's manual ver. 1.0
copyright 2023-2027 META ONIX, all rights reserved
WARNING:
this is an extremely abnormal product. If you purchased it
expecting to get “moogy” or “con entional” filter sounds, you
will be sorely disappointed.
CAUTION: to reduce the risk of electrical shock, do not disassemble.
DANGER! DANGER! HIGH OLTAGE INSIDE. There is a 48v dc supply
internally. No user serviceable parts inside. Refer servicing to qualified
service personnel.
DETAILED SAFETY INSTRUCTIONS:
All the safety and operation instructions must be read before the RK8 is operated. If you don't read and HEED
them, you are a MORON and you deserve to be raped by a 400 pound brony.
RETAIN INSTRUCTIONS: The safety and operating instructions should be retained for future reference.
HEED WARNINGS: All warnings on the RK8 and in the operating instructions should be adhered to.
FOLLOW INSTRUCTIONS: All operating instructions should be followed.
WATER AND MOISTURE: The RK8 should not be used near water (e.g. near a bathtub, washbowl, kitchen sink,
laundry tub, in a wet basement, near a swimming pool etc., ya stupid bastard). Care should be taken so that
liquids are not spilled onto or near the enclosure.
ENTILATION AND COOLING: The RK8 normally operates ERY warm to the touch. It MUST be situated so that
its location or position does not interfere with convective cooling.
The RK8 MUST NOT be used on a bed, sofa rug or similar surface which may prevent proper cooling. It is NOT a
toy, AND IT IS NOT A DILDO. If the RK8 is mounted in a rack or other built-in installation, space must be left
around it to allow convection from the case.
HEAT: The RK8 MUST be situated away from heat sources such as
radiators, heat registers, stoves, or other devices (including power
amps) that produce heat. We DO NOT recommend leaving the RK8
powered up for long periods.
POWER SOURCE: The RK8 should be connected to a Eurorack power supply of adequate capacity. It uses about
1400 mA on power-up and 600 mA after warming up fully from the +12v line. DO NOT attempt to use low cost
power supplies.
POWER CORD PROTECTION: Power supply cords should be routed so that they are not likely to be walked on or
pinched by items placed upon or against them.
CLEANING: The RK8 should only be cleaned with a soft cloth moistened with water. Unplug the power supply
before attempting to clean.
NON-USE PERIODS: The power supply of the RK8 should be unplugged from the outlet when left unused for a
long period of time.
DAMAGE OR TUBE REPLACEMENT REQUIRING SER ICE:
The RK8 should be serviced by qualified service personnel when:
-The RK8 has been dropped, physically damaged, or subjected to force;
-Liquid has been spilled onto the RK8 or it has been exposed to rain;
-The RK8 does not appear to operate normally or exhibits a marked change in performance.
!"#$%& '%!!
METASONIX LIMITED WARRANTY and standard legal disclaimer
Thank you for purchasing this Metasonix product. And for not whining about “problems”. The following terms and conditions apply:
1. Warranty period is for one year from date of purchase with proof of purchase submitted. Warranty covers electrical failure of vacuum
tubes and gas-filled tubes, except in cases explained in 3 below.
2. Operating instructions must be followed. This device was intended ONLY for use by AUDIO AND MUSIC PROFESSIONALS. IT IS NOT
INTENDED FOR USE BY ORDINARY CONSUMERS!!
Product must not have been damaged as a result of defacement, misuse, abuse, neglect, accident, destruction or alteration of the serial
number, improper electrical voltages or currents, repair, alteration or maintenance by any person or party other than our own service facility
or an authorized service center, use or installation of non-Metasonix replacement parts in the product, or the use of this product outside of
the U.S.A. or Canada, or modification of the product in any way, or incorporation of the product into any other products, or damage to the
product caused by accident, fire, floods, lightning, or acts of God, or any use violative of instructions furnished by Metasonix. It is also not
intended for use as a condom-warmer.
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DO NOT OPEN THE RK8 unless you're a service technician.
NOTE: All sales are FINA , especially custom designs. Only a Metasonix authorized dealer is permitted to return
products to Metasonix for a refund or exchange.
WHAT IT DOES
WARNING: The RK8 is not intended to serve as a “general purpose” synthesizer
filter. It is something you have NE ER seen before. It can NOT be compared to
any other product, ever made, PERIOD. Do not walk into this with
“preconceptions”.
Also, please do not power it up, experiment for a few minutes, and then quickly
contact us, claiming it is “broken” or “bad”. Each new RK8 was tested at the
factory very carefully and shipped with plenty of padding. Many of our past
products were often returned with a warranty claim that they were “broken”. And
most such “broken” units turned out to be working perfectly. We will publicly
mock anyone who returns a working RK8 claiming it is “broken”.
The RK8 contains six bandpass filters, which use vacuum tubes. They are
simple “twin T” designs. Each filter is about one octave lower in range than the
one to the left—treble on the left, bass on the right.
Each filter may be manually swept with its own separate tuning knob, over
approximately one and one-half octaves. Or ALL the filters may be swept
together, using either the “MANUAL TUNE” knob, or the C input, which
overrides the knob when a patch cable is inserted. Although it is capable of
some conventional swept-filter effects, the RK8 is more useful as a complex
equalization system or for unique special effects.
Resonance is separately adjustable for each filter. Usually the treble filters will
resonate strongly and oscillate under some settings. The bass filters might not.
Inputs and outputs are compatible with all Eurorack and other modular
synthesizer equipment. The output peak voltage is limited to the supply rails and
can’t damage other modules.
Don’t assume you know what you are getting here—the RK8 is unlike anything
else ever marketed. Also don’t expect it to track COs, its voltage-to-frequency
curve is “more or less” hertz-per-volt but can’t really be guaranteed. The six
vactrols in each RK8 were hand-matched, but can’t be expected to remain
matched, or to track together perfectly.
Again, everything about the RK8 is abnormal. It is not perfectly “clean” and
perfectly “distortionless”, and it cannot be made so. Because it uses vacuum
tubes.
SUGGESTIONS FOR USE by Mike Weeks
In inaccurately simple laymans terms - the RK8 functions as a 6 band “EQ” – run
a signal into the input, with the input/tune/resonance knobs more or less at
12:00, and you will get a colored but somewhat “neutral” tone (hahahahaha).
Each band can then be adjusted (volume/gain – center frequency and
resonance) to shape the sound like an evil equalizer. Right is bass, left is treble,
you know what to do.
That alone is enough to give you incredible ability to make sounds and tones
(even non-staccato sounds) come through as “punchier” and more harmonically
aggressive. It’ll give your TikTok video soundtrack that extra push.
With that logic – you can run anything through it – drum loops, pads, leads, blah
blah blah. Try any source material that is harmonically rich and get a feel for
each band in isolation, then add/subtract bands for more complex filtering
tonalities.
BUT things get REALLY interesting when you inject some C sources into the
C input. The C input controls ALL of the bands, so the relative position for
each filter center frequency can be modified dramatically by the modulation
source coming in, relative to the starting point. LFOs do what you’d expect them
to, but noise sources or other modulation types (including audio rate oscillators)
will get you going in unique directions as well. Using a complex waveform LFO
will animate the RK8 in unique ways and add layers of complexity you would
NOT be able to attain with a standard filter.
Through the prototyping phases, we determined adding individual C control
over each band was not worth the board space that didn't exist, and sweeping all
simultaneously gives a series of discrete emphasis effects across a wide range
of frequencies that truly makes this device unique.
And if you have more modules than sense, the individual outs make this a
DREAM for parallel processing of frequency bands. This is a drone composers
wet dream – take each frequency band and input into various effects units:
reverb, delay, further filters in series, or distortion, and take what was one signal
and make it into a cascading wall of nightmares.
Another experimental possibility: The RK8 is not really intended for use as a
vocoder though it could give ERY crude vocoder-like effects if one feeds
either: the output of an envelope follower, or a vco on its low bass range and
tracking a keyboard, into the C input. It's totally unique. There is literally no
other device that does what this does, not in the modular world and not really
anywhere in pro audio. A tube vocoder would be possible but horribly
expensive. And LARGE.
Honestly, if we have to tell you how to do any more than this, you’ve clearly
wasted your money and you should have stuck with software with presets.
MAINTENANCE
The tubes are being run conservatively, and should last for many, many, MANY years. You
WILL NOT need a new set of tubes for a long time/never, if the RK8 is treated carefully and
used in a conservative fashion. Do NOT rush around looking for spares immediately. Do NOT
listen to guitar amp “tech gurus”. They know very little, and have never seen this circuit
before.
All the tubes in the RK8 are 5702 subminiature pentodes. As of 2023 they were very easy to
find on eBay. But you will probably never need replacements, unless you are clumsy and
break one. The tubes are soldered into the board so soldering equipment is needed to replace
any of them.
Please, we beg you, check with us BEFORE YOU DO SOMETHING STUPID. Thank you.
The tubes in the RK8 MUST be of the correct type, because their heaters are connected in a
series-parallel arrangement. DO NOT MIX OR EXPERIMENT WITH THE WRONG TUBE TYPES.
Do not do stupid things, or you will DAMAGE the RK8 and we will be angry at you.
Use ONLY the Eurorack power supplies we recommend to power the
RK8. Inexpensive ones will not work. Experiment at your own risk.
Technical specs
Audio output: 1000 ohm unbalanced, suitable to drive 600-ohm inputs, maximum level +20dBm.
C input: maximum range -5v to +10v DC. The C will respond only to positive control voltages of
about +1.5v to +5v. Usable sweep depends on settings of Tune controls. All controls may interact
with unrelated controls slightly. Individual audio outputs for each filter may not be fully isolated from
the other filters. C is not fully isolated from the outputs. There may be hum, noise and crosstalk on
all inputs and outputs -- get used to it. It's vacuum tubes, and tubes are evil and unruly little bastards.
Because there are six tubes, the RK8 draws considerable power from the +12v line: up to 1400 mA
when powered on cold, and about 600 mA after warm-up. 12v power requirement is less than 10 mA.
The RK8 contains its own plate supply generator to make +48v for the tubes. The inputs and outputs
CANNOT damage other electronics, the output voltage swing is limited to +-10 volts.
It's an extremely primitive filter thing, and if you don't like that, we can only say: why did you buy the
damned thing? And then we will say, send it back immediately, we have plenty of other customers
who want one. Don’t care about your neuroses.
(text is copyright 2023-2027 Metasonix. All rights reserved. It is a violation of federal law to reproduce, reuse or duplicate
this publication without the express written permission of Metasonix or its assigned representative.)
(Oh, you want to FIX it? You say you want a SCHEMATIC?? Oh, that's PRICELESS. Contact us at METASONIX. 495 N.
Main #109, Lakeport CA 95453, (707) 245-9162, synth@metasonix.com or metasonix@gmail.com. We'll arrange for
repair, while refusing to give you a schematic. The circuit of this bastard thing is so INSANE, we didn't write it down
anyway.)
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