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PREAMP VOLUME – This control sets the volume of the preamp after the Input and Gain stages but before the EQ,
Contour and Master Volume controls. Use this control in conjunction with the Gain Control.
CONTOUR – The Contour control alters the response of the preamp’s inherent voicing by decreasing midrange and
increasing bass and treble as the control is adjusted clockwise from the minimum or at position.
ACTIVE EQUALIZATION – The CONTOUR™500 contains an active 3 band equalizer with sweepable parametric
mid range frequency control. This equalizer, similar to those found on professional sound consoles, is a very useful tool.
The low frequency EQ section is an 80 Hz shelving curve with 15dB of cut or boost. The high frequency EQ section is a
4 KHz shelving curve with 15dB of cut or boost. The parametric sweepable-mid frequency section features 15 dB of cut
or boost with a bandwidth approximately 1 octave wide. The center frequency of this lter is continuously user adjustable
from 150 Hz to 2 KHz with a single control. This lter is typically (but not always) used to reduce or remove offending
frequencies in the instrument’s pick-up response, or boost response to achieve a particular voicing. Spend some time
experimenting so that the process becomes creative as well as corrective. Note that our active equalizers are very wide
response and a little bit can go a long way.
AUX INPUT – A 1/4” unbalanced line level Auxiliary Input is provided that sums directly to the main output bus, controlled
by the master volume control. This input is ideal for practicing with recorded tracks from a CD player, IPOD, or MP-3
player. This input is a tip-ring-sleeve type jack with built-in summing resistors that sum left and right signals when used with
a stereo cable. This input will also work with a mono tip-sleeve plug. Adjust the level of the playback source to balance
with the bass guitar’s volume.
MASTER VOLUME – The master volume control adjusts the overall volume of the amplier and the aux input. Typically,
best results are obtained when this control is operated between the 9:00 and 3:00 positions.
OUTPUT LIMITER – The CONTOUR™500 contains an internal power amplier “Soft Clip” limiter. This limiter allows
simulation of tube output stage saturation as the amplier nears it maximum power. The limiter is a compound multi stage
analog circuit, is quite graceful in nature, and is particularly musical sounding, even when driven hard. The output “LIMIT”
LED shows limiting action at the maximum power threshold and then indicates power amplier clipping as the power
amplier gradually transitions into gentle clipping.
POWER AMPLIFIER – The CONTOUR™500 uses a state of the art, class D power amplier design and a high frequency
switch-mode power supply (SMPS) to achieve unprecedented high performance and lightweight packaging. Switch-mode
power supplies convert the AC line directly to high voltage DC, then the precision PWM (pulse width modulation) inverter
creates a new AC power signal at a frequency more than 1000 times higher than the original wall frequency of 50/60Hz.
This new high voltage, high frequency power signal is then fed into a custom high frequency transformer that steps
the voltage down. A high frequency rectier and low ESR lter capacitors nish the process off by converting the high
frequency AC signal back to the DC voltages that the amplier’s internal circuitry uses. One advantage of this conversion
process is that the DC power supply rails are refreshed more than 1000 times more often than in traditional linear supplies,
thus reducing annoying hum in the audio signal. The high frequency switching is used to reduce the size and weight of
the magnetic and lter components while increasing the performance by recharging the power supply rails more often.
The class D amplier uses digital PWM techniques similar to those in more familiar digital to analog converters to reduce
the size and weight by a factor of 10 times that of a comparably rated conventional class AB amplier. Essentially, a class
D amplier converts the analog signal into a logic level PWM digital signal with an analog to digital converter then level
shifts this PWM signal up to a higher voltage and current and then reconstructs the analog signal by passing it through
what is essentially a power digital to analog converter. Additionally, we developed our own, proprietary limiting and signal
processing techniques to give a distinctly analog feel and sound to the class D platform. This system provides exceptional
performance for low frequency applications such as bass guitar.
HEADPHONES – A 1/4” TRS jack is provided for connection to headphones. A speaker load is not required. Do not
connect this output to anything but headphones. The internal speaker DOES NOT automatically shut off when using the
headphones. For silent practice use disconnecting the rear panel speaker connection is required.
MASTER SECTION STATUS INDICATORS -
• The blue “OPERATE” light indicates that the amplier is ON and the low voltage power supplies are active.
• The red “PROTECT” LED indicates that the amp is in “protect” mode. This LED may ash during power turn-on and turn-
off. This is normal. It will also illuminate during any internal fault condition. If this happens, turn the amp off and consult a
repair technician.
• The amber “LIMIT” LED indicates that the power amp is near its maximum power and has entered its soft clip/limit
mode. Under high output conditions this LED will light with the strongest pulses of the signal. Driving hard
beyond this point will cause the amplier to gradually begin to clip.
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