Fostex 250 - Main Panel Features

MAIN PANEL FEATURES
Input Channel (same features for
channels 1 through 4)
1. INPUT FADER
This slide fader controls the signal level
from either of two sources, the channel's
input jack or playback from the built-in
cassette recorder, depending on the
position of the INPUT selector (LINE/
MIC-TAPE) switch [3], To ensure low
distortion and preserve an optimum
signal-to-noise ratio, the Input Fader
should be set in the range between #7
and # 8 on the scale (nominal position).
When the INPUT selector switch [3] is
in LIN E/M 1C position, the LINE-MIC
(preamp trim) control [2] also affects
the channel level.
2. LINE-MIC (PREAMP TRIM)
CONTROL
This rotary control continuously adjusts
the preamplifier gain over a 50 dB range.
In LINE position, the preamp has 0 dB
gain (unity), which means the channel
input is suitable for use with nominal
- 10 dB (0.3 V rms) line levels such as the
output of electronic musical instru¬
ments and tape recorders. As the con¬
trol is rotated toward MIC position, the
gain increases by 50 dB, making the
input suitable for use with nominal
-60 dB (1 mV rms) levels such as the
output of a dynamic microphone. Inter¬
mediate settings are suitable for such
signal levels that might be obtained
from condenser microphones, guitar
pickups, and so forth.
This control has no effect when the
INPUT selector (LINE/MIC-OFF-TAPE)
switch [3] is set in TAPE position.
*NOTE: Each feature in this section is
referenced by a numbered callout and a
correspondingly numbered description.
When a feature is mentioned, its callout
number may be cited in brackets (e.g.,
the LINE-MIC control [2]).
3l INPUT SELECTOR (LINE/MIC-
OFF-TAPE) SWITCH
This 3-position lever type switch selects
the signal which is applied to the input
FADER, as explained below:
LINE/M 1C: Signal is applied to the
FADER (line to mic level) via
the front panel INPUT phone
jack, and a preamplifier. The
H 1 INPUT jack (front panel)
goes to the H 1 input FADER,
etc.
OFF: No signal is applied to the
input FADER, so the channel
’ is effectively shut off.
TAPE: Tracks 1 through 4 of the
built-in cassette recorder
are connected to the corres¬
pondingly numbered input
channels as follows:.
a) When the track is not
recording, the playback
signal is applied to the
input FADER.
b) When a given track is
actually recording, record
input signal is present at
the input FADER.
4. EQUALIZER (300 Hz & 4 kHz)
The channel’s two EQUALIZER knobs
(300 Hz & 4 kHz) provide approximately
12 dB of the shelf type boost or cut at
a turnover of 300 Hz; and boost or cut
at a center frequency of 4 kHz. Center
position (12 o’clock) provides a flat re¬
sponse. The 300 Hz knob controls bass
frequencies, while the 4 kHz knob
affects mid-range to higher frequencies.
5. 4 CHAN BUSS PAN POT (L-R)
The input signal, after the FADER and
EQUALIZER, is applied to this PAN pot,
labelled L-R. PAN then applies the signal
to a pair of record tracks, either 1 and
2 or 3 and 4, based on the setting of
the 4 CHAN BUSS selector (1-2/3-4)
switch [6],
Center PAN position (12 o’clock rota¬
tion) applies equal signal to both
selected tracks. As the PAN pot is ro¬
tated counterclockwise, it applies about
3 dB more signal to track 1 (or 3) and
virtually eliminates the signal applied to
track 2 (or 4). The opposite occurs when
the PAN pot is rotated clockwise.
NOTE: The 4 CHAN BUSS pot may be
bypassed, and the input can be applied
directly to one (or more) record tracks
by connecting a cable from the chan¬
nel DIRECT OUTPUT to the desired
RECORD INPUT(s), and setting the 4
CHAN BUSS selector (1-2/OFF/3-4)
[6] to OFF position.
NOTE: When recording or overdubbing
one track at a time, it is recommended
that this pan pot be set fully to one side
or the other in order to apply all the
channel’s signal to a single track. Pan¬
ning to intermediate positions is general¬
ly used during mixdown, at which time
two tracks are assigned as a stereo pair
(e.g., tracks 1 and 2), and the pot then
pans the signal left, right, or anywhere
in between. This can also be done
when recording original stereo tracks,
or when overdubbing in stereo.
6. 4 CHAN BUSS SELECTOR
(1-2/OFF/3-4) SWITCH
This lever type switch determines
whether the channel's 4 CHAN BUSS
PAN pot [5] applies signal to recording
busses 1 and 2 or to busses 3 and 4.
The switch is off in mid position, which
means that no signal from the PAN pot
is applied to any recording buss.
7. AUX BUSS
This control feeds the input channel’s
post-fader and post equalizer signals to
a summing amplifier that mixes the Aux
Sends of all four input channels for feed
to the Aux Send jack. This mono mix
may be used to feed external auxiliary
signal processing equipment.
a MONMIX
This controls the recorder output signal
fed to the summing amplifier. All four
recorder output channels are mixed into
mono by the summing amplifier for feed
to the MONMIX jack.
This mono MONMIX signal is generally
used as a cue signal to the musicians.
The recorder’s four channel outputs will
be derived from the tape out signal
when in the play mode, and record input
signal when in the record mode.
VU Meiers and Meter Selector
9. VU METERS
The four VU meters are identical,
illuminated meters with standard VU
ballistics (meter levels relate to the
perceived loudness). A red LED in the
corner of each meter illuminates when
the instantaneous peak level ap¬
proaches the clipping point, providing a
better means to avoid distortion than
the slower-responding meter.
Typical meter readings should peak at
from -3 VU to 0 VU, although per¬
cussive or plucked instruments may
require lower average readings in order
to avoid distortion during the initial
high-level transient. As a rule, occa¬
sional flashes of the LEDs are accept¬
able, but levels should not be so high
as to cause frequent flashing or continu-
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