Primova GKFX-21 User manual

GKFX-21 Subsonic Filter 1
GKFX-21
Subsonic Filter
USER’S MANUAL
Rev. 201 -04-14

GKFX-21 Subsonic Filter 2
Table of Contents
INTRODUCTION ......................................................................................................................... 3
HEX FILTER ................................................................................................................................. 4
13-PIN CONNECTORS ................................................................................................................. 5
GTR IN JACK ............................................................................................................................... 5
VOLUME CONTROLS .................................................................................................................. 5
MIX OUT JACK ............................................................................................................................ 5
S1/S2 JACK .................................................................................................................................

GKFX-21 Subsonic Filter 3
GKFX-21 Subsonic Filter
INTRODUCTION
The GKFX-21 is to be connected between a 13-pin guitar and a synth unit. The synth
unit provides power to the GKFX-21.
Make sure to connect the guitar to IN and the synth unit to OUT, otherwise either
unit may be damaged. Do not turn on power until all connections are made.
This pedal combines six analog subsonic filters with an additional input jack, mix
output jack and S1/S2 control jack (stereo connector for FS- or FS-7 dual foot
switch).

GKFX-21 Subsonic Filter 4
HEX FILTER
The GKMX-21 contain specially designed hex high-pass filters to improve PCM/COSM
tracking and ghost note immunity as well as lowering noise when palm muting. Most
noted effect on GR-55 and VG-99 when using Piezo 13-pin guitars.
This filter is not intended for bass or other instruments than guitar.
The filters are analog and introduce no additional latency. This unit has the same
characteristics as other Piezo filters on the market. Every unit is carefully hand-built,
tested and measured.
The Subsonic Filter consists of six filters (one for each string), eliminating rumble and
low frequency noise. The High-Pass filters remove frequencies below:
50Hz (string E and A),
75Hz (string D and G)
100Hz (string B and High E)

GKFX-21 Subsonic Filter 5
13-PIN CONNECTORS
The 13-pin connectors are soldered to a printed circuit board. Please do not use
more force or violence than required.
Connect the Guitar to the connector marked “IN” and a Guitar Synth to the output
marked “OUT”. Do not turn on power until all connections are made.
The current consumption is abt. 50 mA (25 mA from the +7V and 25mA from the -7V
rail provided by synth unit)
GTR IN JAC
The GTR IN jack allows you to connect any audio source and mix it with the pin 7 (GK
GTR) signal. The audio source may be a second regular guitar or signal from
secondary pickups on your instrument. You may also consider using the two-cable
method and use a high quality guitar cable connected to your regular 1/4” guitar jack
for richer harmonics (the regular pickup signal (pin 7) through a GK cable is known to
damp higher frequencies).
If a regular guitar is connected only effects not related to hex processing can be used
in the synth unit.
VOLUME CONTROLS
The unit has two potentiometers to control:
A) The volume of the GK pin7 regular guitar signal (marked GK GTR)
B) The volume of the signal from the GTR IN jack (marked JACK)
When the pots are in the minimum position (anti-clockwise) no sound will be
reproduced. In the mid position the gain is x1 (+0dB) and if set to max position the
gain is x2 (+ dB). Each input has an active input stage.
The mix of these two inputs is sent to pin 7 of the output GK connector (the
dedicated pin for regular pickups).
MIX OUT JAC
The jack marked “MIX OUT” allows you to “hi-jack” the mix of GK GTR and JACK input
signal. Connect this jack to a guitar amplifier or other high impedance device for high
quality sound un-polluted by digital signal processors.

GKFX-21 Subsonic Filter
S1/S2 JAC
The jack marked S1/S2 allows you to connect a Roland FS- or FS-7 compatible dual
footswitch to control the S1 and S2 commands to the synth unit. Here you must use
a stereo cable. The stereo jack has three connections:
TIP: When momentarily connected to ground (Sleeve) this corresponds to a S2
command (GK connector pin 11).
RING: When momentarily connected to ground (Sleeve) this corresponds to a S1
command (GK connector pin 10).
SLEEVE: Ground
USING A FS-6 (The FS-6 needs separate power to operate with GKFX-21) :
Set switch to: Momentary
A-Patch down
B- Patch Up
USING A FS-7 (The FS-7 needs separate power to operate with GKFX-21) :
Set switch to: Momentary
A-Patch down
B- Patch Up
GTR Jack input impedance: 1 MΩ
Power Consumption: 24 mA
WARRANTY
PRIMOVA WARRANTS THE GKFX PRODUCT FOR ONE YEAR. TWO YEARS IF INSIDE EU.
IMITATION OF IABI ITY AND WARRANTY
NO WARRANTIES OF DAMAGES TO CONNECTED EQUIPMENT OR CABLES.
NO WARRANTIES IF UNSUITABLE VOLTAGE HAS BEEN APPLIED TO CONNECTORS.
PRIMOVA AB ONLY WARRANTS THE GKFX UNIT ITSELF.
CONNECTING THE GKFX UNIT OR THE GKFX BOARD, TO COMPONENTS SUCH AS GUITARS OR
SYNTHESIZERS IS AT OWN RISK.
IN NO EVENT WILL PRIMOVA BE LIABLE FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR THE INABILITY TO USE THE GKFX-UNIT EVEN
IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. IN PARTICULAR, PRIMOVA IS NOT RESPONSIBLE
FOR ANY COSTS INCLUDING BUT NOT LIMITED TO THOSE INCURRED AS A RESULT OF LOST PROFITS
OR REVENUE, LOSS OF USE OF THE GKFX PRODUCT, LOSS OF DATA, THE COST OF SUBSTITUTING THE
GKFX-UNIT, OR ANY CLAIMS BY THIRD PARTIES.
© Copyright Primova AB Sweden 2015-201
PRIMOVA AB
Kurlandaallén 21
8151 Kristinehamn, Sweden
www.primovasound.com, email: [e-mail]