Hartke B90 Owner's Manual page 6

Guided Tour - Front Panel
4. Low EQ control - This control provides approximately 15 db of cut or boost at 100 Hz,
with a peak (bell) curve. When the knob is at the 12 o'clock ("0") position, there is no
boost or attenuation (that is, flat response). As it is turned clockwise from the "0" position,
the frequency area is boosted; as it is turned counterclockwise from the "0" position, the
frequency area is attenuated. For more information, see the "Using Equalization and
Shape" section on page 8 in this manual.
5. Mid EQ control - This control provides approximately 15 db of cut or boost at 830 Hz,
with a peak (bell) curve. When the knob is at the 12 o'clock ("0") position, there is no
boost or attenuation (that is, flat response). As it is turned clockwise from the "0" position,
the frequency area is boosted; as it is turned counterclockwise from the "0" position, the
frequency area is attenuated. For more information, see the "Using Equalization and
Shape" section on page 8 in this manual.
6. High EQ control - This shelving control provides approximately 15 db of cut or boost
at 5 kHz. When the knob is at the 12 o'clock ("0") position, there is no boost or attenuation
(that is, flat response). As it is turned clockwise from the "0" position, the frequency area
is boosted; as it is turned counterclockwise from the "0" position, the frequency area is
attenuated. For more information, see the "Using Equalization and Shape" section on
page 8 in this manual.
7. Line Out - This standard unbalanced 1/4" jack provides a line-level post-EQ and
post-Volume (and, in the B60, B90 and B120 models, post-Shape) output signal from the
B Series. You'll usually use this to connect the B Series signal to a line-level input when
interfacing with PA systems or recording mixing consoles. The signal from this output is
the same as that from the Preamp Out on the rear panel (see #3 on page 5).
8. Headphones jack - Connect any standard stereo headphone (600 ohms or less) to
this standard 1/4" stereo jack. When a plug is inserted into the headphone jack, the
speaker output is disconnected, allowing you to use your B Series as a practice amplifier.
The level of the signal sent to the headphones is determined by the setting of the Volume
knob—at the point where a connected speaker would clip, the headphones will clip.
WARNING: Because even the smallest B Series amplifier is capable of generating
extremely high headphone signal levels, always start with the Volume knob at
minimum and then slowly turn it up. In particular, a clicking sound is an indication
of distortion and possible damage to the headphones (and/or your hearing!); don't
let things get to that point!
9. Power switch - Use this to power the B Series on or off. When powered on, an LED
inside this switch is lit.
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