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Power Supply and Power Supply Connections
The recommended option is to use an insulated plugtop (often called a wallwart) AC adapter.
They are used external to the Filtrex housing and plug into the Filtrex using the two pole
barrel connector. They are very safe since all the dangerous high voltage stuff is kept inside
the wall-wart.
You need a 15V or 18V alternating current (AC) output at 250mA or higher rating. Do not
use a DC output type. Although the latter are the most common type of wallwart for guitar
effects pedals, they will not work with the Filtrex. To reiterate, because this is really
important, it must say 15VAC or 18VAC on it somewhere.
Finding such a power supply is not always as easy as it should be. So many plugtop supplies
these days are switch mode DC output types. However, unregulated AC output ones are out
there and most decent electronic parts suppliers will have them, as well as online guitar effects
shops and even some music shops. Since a wallwart supply will have its own mains plug built
into the case it's not practical for me to list an example for every country out there. In addition
listing a part number for a generic power supply is a bit like a game of whack-a-mole as the
moment I give the part number that very part will disappear and a new one with a different
part number will appear. If you do get stuck it may be best to ask on the forum and see what
other members suggest. That said if you are in the UK and have a Farnell account you could
try their part number: 2368009.
Some 12V AC output types may also work but this is only because some AC output wallwarts
tend to be poorly regulated and have a lot of overhead. Do be aware that if they do work
some of the time they may not work all of the time. If the voltage does fall below the required
operating voltage of the Filtrex-II the most obvious sign is an audible hum from the outputs.
You will not damage the Filtrex-II by doing this although any connected amplifier or speaker
system may object to the humming.
To connect your wall wart to the Filtrex you need a suitable chassis mounting connector. You
must ensure you get one that has a plastic housing and plastic mounting bush. This means that
there should be no electrical contact between the case and the power socket. Do not get one
that has a metal mounting bush as this will inevitably connect one of the AC connections
directly to the case.
Make sure too that you get the right socket for the plug you have on the wall wart. Some wall
warts give you a little bundle of different types to choose from. Ensure that the socket you get
allows the plug to slip in easily yet not break connection when wiggled gently. If you are
making up your own plug for it, since it is AC, it does not matter which wire goes to what.
There is no + or -.
Once fitted to your case the socket must then be connected to the PCB. One terminal goes to
AC1 and the other goes to AC2 on the PCB. If your wires are longer than 100mm or so then
it is a good idea to twist them together. This reduces the amount of radiated noise from the
wiring.
AC3 and AC0 are left unconnected.
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