FRONT PANEL
INPUTS
- The Shenandoah™ Acoustic Pro LT is equipped with two types of input jacks. The ¼” input is unbalanced
and “line/instrument level” with a useable sensitivity from 50 mV to 1 volt. The input impedance is 150 k ohms. The
¼” input will also accept most active balanced line sources, automatically unbalancing them by recognizing the tip
portion of the balanced signal. If an instrument offers an unbalanced output it should be connected to the
unbalanced input of the Shenandoah amp. Additionally, the precision input scaling preamp contains a 45 Hz, 12
dB/octave high pass filter (more effective and less intrusive than the more common 6 dB filters) and an “RFI” filter
(radio frequency interference) to eliminate unwanted noise. The XLR input jack is balanced and “microphone
level”, with a useable sensitivity from -60dBv to -30 dBv. It is not a line level input. It contains a precision full range
differential microphone preamp with phantom power. For use with higher-level sources (such as the balanced line
level output from a keyboard or other instruments), a balanced pad network will be necessary to use the balanced
input. For instance, a Rapco “Pad Blox”, -20 or -30 pad or similar product could be used.
PHANTOM POWER
- An internal phantom power source (13.6 volts) is provided for use with condenser mics. This
power source is on at all times and does not affect the standard operation of the amp, even when a condenser mic
is not used. We use the DIN 45-596-P12 volt standard, which will operate virtually all of the live sound
reinforcement condenser microphones on the market. Some “boutique” externally biased condenser mics will not
be compatible and will require 48 volt phantom power. Some suggested live sound condenser mics: AKG (C4500B,
C4000B ,Elle C, C5), Audio Technica (AT3035, 3032, ATM 710), CAD (C195-P12), Shure (SM2-86, SM 48) and
Crown (CM-200A, CM200-ASW, CM-310A, CM-310ASW).
PREAMP GAIN CONTROL
– This level control sets the amount of gain at the Input of the Preamp. Use this control
to set the input level in conjunction with the overload LED indicator.
INPUT CLIP LED
– The Red Clip LED senses the input signal to the preamp section and warns of input overload.
For the cleanest signal possible this LED should only flash with the strongest signal peaks. Adjust this sensitivity
with the input volume control.
PHASE SWITCH
– Each input is provided with a phase reverse switch. By reversing the phase of the input signal,
feedback tendencies can be reduced if caused by sympathetic vibrations between the speaker and the instrument.
Under some conditions, changing the phase can drastically improve the output from the amplifier and can improve
the playability of some instruments.
FET/TUBE PREAMP BLEND CONTROL
– Each input channel is provided with a preamp blend control, which
adjusts the balance of the input signal between the FET and 12AX7 TUBE preamp. The FET preamp produces
smooth, articulate response while the TUBE preamp enhances the acoustic guitars timbre with the warm tonal
characteristics of the TUBE but without distortion when driven hard. It will be helpful to experiment with this blend
control to find the position that best suits your desired tone and playing style. The ability to choose or mix these two
preamps is a unique and exceptional feature of the Shenandoah™ Acoustic Pro LT amplifier design. Note: From a
cold start, it will take 7—10 seconds for the tube to warm up and pass audio.
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