METASONIX RK5 DUAL User manual

RK5 DUAL
LOWPASS GATE
user's manual
Copyright 2017 Metasonix. All rights reserved.
Please read all of this before using it!
RETAIN INSTRUCTIONS: The safety and operating instructions should be retained for future reference.
EED WARNINGS: All warnings on the RK5 and in the operating instructions should be adhered to.
FOLLOW INSTRUCTIONS: All operating instructions should be followed.
WATER AND MOISTURE: The RK5 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.). Care should be taken so that liquids are not spilled onto or near the enclosure.
VENTILATION AND COOLING: The RK5 normally operates warm to the touch. The tube generates considerable heat. It MUST be
situated so that its location or position does not interfere with convective cooling. The RK5 MUST NOT be used on a bed, sofa rug
or similar surface which may prevent proper cooling. It is NOT a toy. If the RK5 is mounted in a synthesizer rack or other built-in
installation, space must be left around it to allow convection cooling. Use great caution if handling the RK5 when it is powered up.
EAT: The RK5 MUST be situated away from heat sources such as radiators, heat registers, stoves, or other devices (including
power amps) that produce heat.
POWER SOURCE: The RK5 should be connected to a power supply ONLY of the type described in the operating manual or as
marked on the RK5. WARNING: Each RK5 requires +12v and -12v at 100mA, with a brief transient consumption of 200 mA at first
power-on. The cabinet power supply must be able to deliver this current. Most available switch-mode power supplies should be
able to handle this load. WARNING: The tube gets hot in normal operation and should not be touched after 10 minutes with power
applied.
CLEANING: The RK5 should only be cleaned with a soft cloth moistened with water. Disconnect all possible power supplies before
attempting to clean or handle.
NON-USE PERIODS: The RK5 should be shut off when left unused for a long period of time.
MEC ANICAL: protect the RK5 vacuum tube from damage. Use of a Eurorack cabinet with a removable lid tall enough to protect
the tube is recommended, if the synthesizer is to be moved or transported. Remove the tube from the socket if the cabinet's lid will
not clear it.
DAMAGE OR TUBE REPLACEMENT REQUIRING SERVICE:
The RK5 should be serviced by qualified service personnel when:
--The power supply has been damaged;
--The RK5 has been dropped, physically damaged, or subjected to force;
--Liquid has been spilled onto the RK5 or it has been exposed to rain;
--The RK5 does not appear to operate normally or exhibits a marked change in performance.
SERVICING: The user should not attempt to service the RK5. All servicing should be referred to qualified service personnel.
METASONIX LIMITED WARRANTY and standard legal disclaimer
Thank you for purchasing this Metasonix product. 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 ONSUMERS!!
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 (except as a product distributed by an authorized Metasonix dealer), 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.
3. Obligations of Metasonix shall be limited to repair or replacement with same or similar unit, at our option. To obtain repairs
under this warranty, present the product and proof of purchase (e.g. bill or invoice) to the authorized Metasonix service center,
transportation charges prepaid. When returning the product for repair, please pack it very carefully, preferably using the original
packaging materials. Please also include an explanatory note.
IMPORTANT:
To save yourself unnecessary cost and inconvenience, please check carefully that you have fully read and followed the
instructions in this instruction manual.
This warranty is in lieu of all other expressed warranties, obligations or liabilities. ANY IMPLIED WARRANTIES, OBLIGATIONS, OR

LIABILITIES, INCLUDING BUT NOT LIMITED TO T E IMPLIED WARRANTIES OF MERC ANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE, S ALL BE LIMITED IN DURATION TO T E DURATION OF T IS WRITTEN LIMITED WARRANTY. Some
states do not allow limitations on how long an implied warranty lasts, so the above limitations may not apply to you. IN NO EVENT
S ALL WE BE LIABLE FOR ANY SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES FOR BREAC OF T IS OR ANY OT ER
WARRANTY, EXPRESS OR IMPLIED, W ATSOEVER. Some states do not allow the exclusion or limitation of special, incidental or
consequential damages, so the above limitation may not apply to you. This warranty gives you specific legal rights, and you may
also have other rights which vary from state to state.
METASONIX shall not be held liable for any incidental, consequential, or direct damages or expenses associated with the use or
misuse of its products. The audio output of this product is capable of damaging some types of solid-state audio equipment; such
use is entirely at the risk of the user. METASONIX does not guarantee that any of its products are designed for any particular use
or purpose. The entire risk of suitability and performance of this product lies with the user. Products manufactured and/or sold by
METASONIX are not authorized for use as critical components in devices used in life support and other systems whose failure or
performance could result in compromised safety or danger to life or property.
NOTE: All sales are FINAL, especially custom designs. Only a Metasonix authorized dealer is permitted to return products to
Metasonix for a refund or exchange.
What it does:
The RK5 is the world’s irst lowpass gate in the style o the original Buchla 292 LPG—except using a vacuum tube instead o op-amps. It
implements the simple “Sallen-Key” lowpass ilter o the 292 with a single triode as a cathode ollower, plus CV control via a pair o Silonex
linear optocouplers. Unless the tube is deliberately clipped, signal distortion will be less than 0.1% and there will be no possibility o
crossover or slew distortion, since the circuit is pure Class A cathode ollower.
The audio inputs have 500k ohm impedance. The CV inputs are about 3k ohms impedance and need to produce at least 3 mA to ully open
the optocouplers. The audio output is able to drive a 10k-ohm load (do not load it down with 600 ohms or you will lose a lot o signal volume).
USAGE
Connect the RK5 to an adequate Euro cabinet power supply. Connect an audio source to one channel’s INPUT, and connect its OUTPUT to
a monitor speaker or headphone ampli ier.
For use as a VCA, connect an envelope generator or other CV source to the channel’s CV input. It should produce ull volume when the EG
is triggered. The gate will be ully closed with 2.0v CV input or less, and opens ully when the CV reaches 5.0v. Between these points, the CV
will make the RK5 channel act like a simple low-pass ilter with two poles. When closed there will be at least 40-50 dB o signal rejection;
when ully open, the output signal will be close to 95% o the input signal level (no, the RK5 does NOT provide any signal gain). It’s tubes,
and it’s BRUTE FORCE, so an RK5 might not completely cut o the signal or balance rom channel to channel. I you expect total muting
when not triggered, use a VCA or a noise gate on the output o the RK5; or cascade the output o one channel to the input o the other.
The two channels are completely independent and should have no audible crosstalk. Note that the 17JK8 tube in the RK5 is a “dissimilar
dual triode” with high perveance, originally intended as a cascode ampli ier in television and radio circuits. This makes it a good cathode
ollower on a low-voltage power supply. Because the two triodes are di erent and the optocouplers vary rom unit to unit, the two channels o
the RK5 will NOT sound exactly identical in operation. Do NOT assume the RK5 is “broken” i the two channels sound di erent when the
gate is opening or closing. This is normal.
Note: The RK5 can NOT be damaged by signal overdrive. In act, it is doubt ul i even a lightning strike or electrostatic shock will damage it.
There are no integrated circuits or transistors in the signal path. There is no high-voltage power supply in the RK5 as the tube operates
directly rom the +12 and -12 rails.
MAINTENAN E
The RK5 requires a power supply producing +12v and -12v DC at 100 mA. When irst powered on, the RK5 brie ly draws greater current, so
be aware o this when using a power supply to run it plus other modules. You MUST assure the power supply is able to handle the RK5 load
plus the load o other modules. Most power supplies on the market should be able to handle this load (although it depends on how many
other modules are being powered rom the same supply)
The tube in the RK5 is being run VERY conservatively. It should last or tens o thousands o hours o normal use. Still, the RK5 tube
produces a lot o waste heat, so we recommend shutting it off when not in use.
UNLESS YOU KNOW EXACTLY WHAT YOU ARE DOING, DO NOT REPLACE OR SUBSTITUTE THE TUBE YOURSELF!
Please note: not all tubes have easily visible heaters. They were not designed to o er pretty cosmetics. I you can't see a heater glowing, DO
NOT assume that tube is bad. I you hear an output signal, the RK5 tube is working. We get many oolish complaints o this type!
TUBE REPLACEMENT: despite its expected long li etime, the tube might be damaged or develop aulty internal wiring connections, requiring
replacement. This particular RK5 was shipped, and wired or, a 17JK8 dual dissimilar triode. It is possible to use a ew other tube types in the
RK5 without modi ication; types with low plate resistance, a heater o 12.6v to 20v, and pinout 9A will work. We would recommend 12AT7s,
12AU7s, 12AV7/5965, or a ew similar types. Be warned that other types will draw more current rom the power supply than the 17JK8 and
may not behave the same way. Experiment at your own risk. We recommend sticking with the original tube type; there is no worry about
inding them, as 17JK8s are still quite easy to ind and are available rom distributors such as Radio Electric Supply ( vacuumtubes.net) or
Antique Electronic Supply (tubesandmore.com).
If you are confused or have ANY technical questions, feel free to contact us. Please DO NOT ASSUME and if you are not an
experienced technician, DO NOT TRY RANDOM TUBES OR MODIFY T E CIRCUIT IN ANY WAY!
495 N. Main #109, LAKEPORT CA 95453 USA
[email protected], www.metasonix.com