Keeley Engineering
Bassist and GC-2 Limiting Amplier
Owners Manual
THANK YOU!
Thank you for purchasing the next generation of Keeley
Compressors, or Limiting Ampliers. The Keeley GC-2 and
Bassist Limiting Ampliers are at the forefront¬ of stomp
box technology, utilizing circuits never before seen in such
a small package. The THAT Corp 4320 IC, a chip developed
by former dbx engineers, has allowed us to produce a
foot pedal compressor that in many ways can equal the
performance of the legendary dbx 160A while consuming
incredibly low power and tting in an unbelievably
small package. The goal of these pedals is to provide
a convenient way of offering real professional quality
compression with the kind of accuracy and transparency
that studio engineers depend on every day. Compression of
this kind can be a strangely complex thing, so please take
time to read through this manual, it may prove quite helpful
when setting up your unit.
BASIC CONTROLS:
• True Bypass Footswitch – Turns the effect on or off. If Blue LED
is lit at the top of the pedal, the controls are active
• COMPRESSION Knob (Ratio) – Use this knob to set the
compression ratio above the threshold. 1:1 represents no
compression, or no reduction above threshold. Innity:1
represents a hard limiter, or zero volume increase over threshold.
• THRESHOLD Knob – Use this knob to set the Threshold,
or trigger point, of compression. Lower settings will cause
compression to occur more often, higher levels will require you
to play harder before compression begins.
• GAIN Knob (Output Level) – Adjust this knob to increase
output level, to compensate for compression reduction, or to
push higher than unity gain or boost.
• Threshold Indicator – This is the LED in the center of the pedal.
This dual color LED will be lit green if there is no compression,
or red when the threshold has been met and the pedal is applying
gain limiting (compression).
STARTING OUT / BASIC SETUP:
• Setting the Threshold: The Threshold control is, in most cases
the rst control to set on a compressor. Signals that surpass the
threshold level in volume will be reduced by the factor set on
the compression control, all signals that don’t meet or exceed
the threshold level will pass through completely unprocessed.
To begin set-up, start with gain set at a moderate level, and
compression set to 1:1. Play music through the pedal noting when
the threshold indicator changes from green to red. The threshold
indicator should not stay lit the entire time in most situations.
For protection against higher than usual peaks, or to use as
a completely transparent limiter, adjust Threshold to a point
where the indicator turns red only under the loudest and most
extreme circumstances, i.e. very hard picking attack, slaps, etc. For
noticeable compression effects, or “always active” compression
sounds, adjust Threshold to a level where every note played
causes the indicator to turn red.
• Setting the Compression (Ratio) control: The compression
control sets the amount of gain reduction that will occur past the
Threshold level. The ratio, refers to the number of decibels that
must be introduced over the threshold level to produce a 1db
increase in output level. So, at a 5:1 ratio, every 5db of increase
in the level entering the compressor above the set Threshold
will produce 1db more output. While this sounds like a very
simple concept, the effects of this can be quite complex. Higher
compression levels will produce a more noticeable “squish” and
will limit dynamics. The lower the compression level, the less
noticeable the effect, the more dynamic range, and the more
“natural” the signal will sound. Adjust this control to nd a
perfect balance for your application.
• Setting the Gain Control: The gain control, as the name implies,
adjusts the output level of the pedal, and amplies it over the
normal signal level. The simple explanation is that it compensates
for the signal level lost as a result of compression. To set it up in
a standard way, toggle the pedal on and off repeatedly adjusting
the gain until you hear no difference in level between active and
bypassed. However, this pedal is capable of a lot of output gain,
+20db to be exact. So, some users may want to run it at a level
above normal to produce a thickening effect with other pedals
or recording equipment in sequence, or to push a quality tube
amp in to breaking up. It makes a great boost pedal. Just give it
a shot! One word of note about the Gain control. If you nd
yourself pushing the gain quite a bit above midway or zero (db)
in order to get unity gain, your threshold is set too low and your
compression level may be set too high. The more gain that is
introduced, the more noise that will be introduced. For the most
quiet operation, adjust threshold and compression settings to use
the lowest amount of output make-up gain possible.
• Attack and Release: This pedal has no attack and release
controls. There is a reason for this. There is a certain gure that
just sounds good as far as compression goes; and that’s 125 dB/
second. With feed forward compressors that use this type of
true-RMS detector you use a single time constant parameter.
The timing capacitor gives you attack and release times that
are adaptive to your playing level or the signal input to the
compressor. Bottom line: Attack and Release times vary on
program content. Attack times are generally speaking, about 100
times faster than release times. Attack Time: typically 15ms for
10dB, 5ms for 20dB, 3ms for 30dB Release Time: typically 8ms
for 1dB, 40ms for 5dB, 80ms for 10dB, 160ms for 20dB, 240ms
for 30dB
EXAMPLES:
This setting works very well as
a noticeable but effective leveler.
Most recommended for Bass guitar
and ngerpicked instruments it
does quite well evening out levels
between strings and fret positions.
One word of note, the Threshold
setting will depend heavily on the
output level of the instrument played,
so it must be adjusted to taste. In
this example, it was set on an active
bass to a point where every note
played triggered the compressor and
it released quickly after the note
began to decay. COMPRESSION:
2:1-5:1 THRESHOLD: Dependent
on Instrument, for ours -30db
GAIN: 0 to +6db
This setting is a good starting place
for electric guitar limiting. One word
of note, the Threshold setting will
depend heavily on the output level of
the instrument played, so it must be
adjusted to taste. Setting Threshold
too low can lead to noise and low
output. COMPRESSION: 2:1-3:1
THRESHOLD: -30db GAIN: To
Taste, 0 to +6 db
This setting is for heavy compression
and limiting. Perfect for lead boosts
or country “Chicken Pickin”.
One word of note, the Threshold
setting will depend heavily on the
output level of the instrument
played, so it must be adjusted to
taste. COMPRESSION: 5:1-10:1
THRESHOLD: -30db GAIN: to
taste, 0 to +4 db
This is a VERY BAD setting. At
this position you will get constant
over-compression, no dynamics and
a signicant level of noise. It is being
included as an example of what
NOT to do. COMPRESSION 10:1+
THRESHOLD: -50db GAIN: +20db
CONTACT US:
RKFX.COM I FX@RKFX.COM I
TOLL FREE: 1-8668-GO-RKFX
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