Ashly SC-40 Operating instructions

 MODEL SC-40
INSTRUMENT PREAMP
OPERATING INSTRUCTIONS
manufacturer of professional audio equipment
I. INTRODUCTION
The Ashly Audio model SC-40 instrument preamp was designed
to help solve some of the problems associated with modern
electronically reproduced music. In particular, it provides
a means of performing the critical first stage of amplification
for a wide variety of musical instruments with an absolute
minimum of noise and signal loss, has provision for the connection
of studio type line-level effects devices, operates with either
line-level power amplifiers or musical instrument amps, and
includes a direct output with a seperate level control for
connection to studio or PA console microphone inputs.
Tone control 1s accomplished using a sophistocated 3-band
tunable equalizer borrowed from our large mixing consoles
making possible a wide range of voicings.
A "peak" indicator warns of approaching overload anywhere
in the preamp and the overload characteristic is one of "clean"
clipping free from spikes or transients.
11. INPUT, OUTPUT, AND POWER CCNNECTIONS
The preamp should be connected to a 3-wire grounded outlet
supplying 120 Volts, 50-60 HZ. Power consumption is 5 watts.
Except for the mic-level PA output, all input and output
connections are standard 1/4" phone jacks which mate with
a standard phone plug such as a Switchcraft model 280. The
mic-level PA output is a 3-pin male XLR connector and is
wired as follows:
Pin 1 Ground
Pin 2 Signal low
Pin 3 signal high
III. FUNCTIONS OF INPUTS AND OUTPUTS
A. INPUT
The front panel input impedance is 2.2 megohms which will
impose virtually no load on any musical instrument, insuring
maximum level and high frequency response. Nominal operating
level is -20 dBV, but levels from -50 to +10 dBV provide good
results. Low or high impedance sources are acceptable.
B. EFFECTS SEND-RETURN
These two jacks may be used to insert line-level effects
or signal processing devices into the signal path. Connect >
the EFFECT SEND to the device input and connect the device
output to the EFFECT RETURN. Low-level effects devices should
be connected between the instrument and the SC-40 front panel
input.
С. STAGE OUTPUTS
Use the HIGH-level output to directly drive a power
amplifier (Crown, BGW, Phase Linear, etc.) and use the LOW-
level output to drive conventional musicel instrument amps.
If you need more or less level and can't correct the problem
by adjustment, try the other output.
D. PA QUTPUTS
Use the mic-level PA output to directly connect the SC-40
to a studio or PA system mixing console microphone input, or
use the LINE-level output to drive a line input. The mic.
connection should be used for long cable runs because it isa
balanced line which helps to minimize noise. (This mic-level
output can be used with any console mic input including
balanced, unbalanced, and phantom powered types.)
IV. OTHER HOOKUPS
With the multitude of inputs and outputs available on
the SC-40, there are many possible variations in its use. A
few are presented here as an illustration. Experimentation will
be necessary to exactly meet individual needs.
1. When not using the PA output as a direct feed, it may be
used to feed a second stage amplifier, with seperate level
control.
2. When taking a line-level feed from another amplifier of
preamp, connect it into the EFFECT return rather than the
front panel input thus bypassing the preamp section of
the SC-40, but still using the equalizer.
3. Smooth distortion may be produced by wiring (2) 1N914 diodes
paralleled in opposite directions between the tip and sleeve
of a phone plug and inserting it into the EFFECTS send.
A foot switch can be wired in series with the tip of the
plug to switch out the distortion.
V. CONTROLS
A. GAIN
The GAIN control adjusts the gain of the input stage of
the SC-40 to accomodate a wide range of input levels. Start
with this control at its minimum setting and increase as
necessary. Decrease the gain if the "peak" indicator
illuminates unless deliberate overdrive is desired.
B. EQUALIZER
The six equalizer controls are divided into three bands.
Each band has a boost-cut and a frequency control. The low
and high bands have a "shelving" type action, meaning that all
frequencies below the low setting and above the high setting are
affected by the boost-cut control. The mid equalizer ia a
"peaking" type, having maximum effect at the mid frequency
setting and less effect on lower and higher frequencies.
Equalization settings will vary widely depending on the type
of instrument, speakers and cabinets used, and the type of
sound desired. It is always a good idea to start with a "flat"
setting as a reference and adjust from this point.
С. PRE-POST
This switch selects the signal sent to the PA outputs. The
PRE position provides a "flat" signal to the PA regardless of the
SC-40 equalizer settings, while the POST position includes
the equalizer in the PA signal. Note that this switch affects
only the PA outputs and that the STAGE signal is always equalized.
As a general rule, use the PRE position if the PA or studio
console has a good input tone control, and use the POST position
if it does not.
D. LEVEL
These two controls independently adjust the levels of the
signals at the PA and STAGE outputs. They should be adjusted to
the desired level after the GAIN and EQUALIZER controls are set.