Maintenance; Technical Specs - METASONIX RK8 Filterwall Owner's Manual

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.
CV input: maximum range -5v to +10v DC. The CV 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. CV 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.)