Electro-Harmonix Black Finger Tube Compressor Instruction Manual
BLACK FINGER
All-tube Optical Compressor
- OPERATING INSTUCTIONS -
Congratulations on your purchase of the Black Finger! The Black Finger is a warm
sounding compressor pedal useful for both guitar and bass, as well as for home
recording. This pedal features an all-tube signal path using two premium 12AX7EH
vacuum tubes. Carefully reading these instructions will ensure that you will get the
most out of your Black Finger.
Included with the Black Finger is a unique 12VAC/1000mA adapter. Use only the
adapter supplied. Using any other adapter can cause harm to you, the Black Finger
and the adapter.
WARNING: There are extremely high voltages in the Black Finger even when
it is unplugged – DO NOT OPEN THE BLACK FINGER.
- THEORY OF OPERATION -
Optical compressors work by treating an incoming signal with an optically controlled
attenuator (a type of volume control) comprised of a fixed resistor and a shunt optocoupled photocell. Because this attenuator is “passive”—as opposed to the more
common “active” AGC (Automatic Gain Control) compressor circuits—it doesn’t add
an electronic signature to the signal, thus preserving the tone and character of the
original sound. Some gain is needed to adjust the output level so that it matches the
original level, and this is accomplished with an all-tube fixed gain pre-amp circuit. In
general, compressors are used to sustain melody lines, minimize changes in signal
level, or add a “forward” percussive effect to instruments or drums.
- CONTROLS -
COMPRESS Knob— Varies the amount of compression from minimum (counter-
clockwise) to maximum (clockwise).
LAMP/LED Switch— Selects the light source to drive the optical attenuator. The
LED is very fast and flat in frequency content. Choose this setting for straight-ahead
compression effects and sustain. Choose LAMP for a slow attack and a reduced
compression on the treble content. This is great for funk chord playing, voice and
keyboards.
SQSH/NORM Switch— Selects between normal attack and a “squashed” long
attack time for the attenuator. This directly affects only the LAMP setting but you will
see a reduction in compression if you leave SQSH on while in LED mode.
PRE-GAIN Knob— Adjusts the amount of signal fed to the attenuator. With this
knob turned toward the minimum (counter-clockwise) position, less of the signal will
pass the compression threshold. This is one way to dial in less effect. More signal in
will mean that more of the signal will pass the compression threshold. This will
maximize the effect when the COMPRESS Knob is turned up, or clip/overdrive the
circuit if the COMPRESS Knob is turned down.
POST-GAIN Knob— Adjusts the level of the OUTPUT signal.
LEVEL LED— Gives a visual indication of the gain reduction caused by the
compressor. The brighter the LED is, the greater the compression.
STATUS LED— Lights up when the Black Finger effect is engaged. If the STATUS led
is off, the unit is in true bypass mode. The footswitch engages/disengages the effect.
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