Fostex 250 - Introduction

SECTION 2 INTRODUCTION
The Fostex Model 250 incorporates a 4 input x 6 output mixer
and a 4 track, 4 channel cassette tape recorder—a com¬
plete recording system (less microphones, monitor amp and
speakers) in a lightweight, compact housing. With the very
portable Model 250, setting up an ‘'instant" recording studio
is as easy in a hotel room or at a friend’s place as it is at
home. The system is ideal for making original multi-track
recordings, overdubbing, and mixing down to stereo. The
Model 250 provides many alternate signal flow paths, thanks
to a variety of assignment switches, pan pots and auxiliary
in/out jacks. This not only provides creative flexibility, it also
enables the unit to serve as a back-up mixer for simple
sound reinforcement applications.
Live instruments and vocals tend to generate high instan¬
taneous peak levels, and sometimes low average levels, both
of which tax the limits of the mixing and recording equipment.
These extremes—the difference between maximum un¬
distorted recording level and the noise floor—constitute the
dynamic range of the program. In commercial recordings
and broadcasts, such extremes in dynamics have already
been compressed by a variety of signal processing. This is
why consumer tape recorders can yield acceptable results
even though they offer limited dynamic range. When making
live recordings, however, the ability to handle wide dynamics
is far more critical. For this reason, Fostex engineers have
given special attention to maximizing the dynamic range of
the cassette recorder and of the mixing electronics.
The result is excellent audio performance, with wide band¬
width (wide frequency response), low distortion and low
noise. To improve tape record/play performance, a new
track/speed format has been adopted. Standard cassettes
are utilized, but the tape head configuration and running
speed are modified for optimum four-channel operation.
HOW 250 RECORDINGS DIFFER FROM STANDARD
STEREO CASSETTES
The tape records or plays all 4 tracks in the same direction at
3-3/4 ips (9.5 cm/s), two times conventional cassette speed,
providing extended high frequency response and wider
dynamic range. Additional dynamic range is afforded by the
built-in Dolby* Type C noise reduction system, an updated
version of Dolby processing that yields approximately 20 dB
of noise reduction and headroom extension.
The Model 250 track format is designed with consideration to
improving sync crosstalk while maintaining interchangeability
with the standard Phillips cassette format.
A tape recorded on tracks 1 and 2 of the Model 250 can
successfully be played on those regular format cassette
decks having a tape speed of 3-3/4 ips; a tape recorded at
3-3/4 ips can be put in the Model 250 for overdubbing, or a
control signal can be recorded on one track for audio visual
applications.
USE THE PROPER TYPE OF CASSETTE TAPE
Fostex has engineered the Model 250 to operate with just
one specific type of cassette: the tape should have a gam-
maferric oxide emulsion and should be rated for high bias
and 70 microsecond equalization. (This is the type of tape
that uses the "chrome" position on many recorders,
although not a chrome tape). There are several benefits in
standardizing on one type of tape. Fostex is able to deliver
the utmost performance, and high reliability, at a moderate
price. Also, the user saves time when setting up to record or
play a tape because there are no routinely required bias, EQ
or level alignment procedures. Moreover, the majority of pro¬
fessional recording engineers choose to standardize on one
tape so that they obtain consistently predictable results.
Metal tape was rejected because it would greatly increase
operating costs without any major benefit (metal tape was
first developed to extend high frequency response at low tape
speeds, but the Model 250 is already running at twice normal
speed). Metal tape also requires significantly higher record
and erase bias, which would compromise track-to-track
separation and erasure depth, both critical to overdubs.
Chrome tape was not chosen because it can cause
premature tape head wear, and because gamma-ferric oxide
formulations afford virtually identical performance.
The gamma-ferric oxide tape specified is widely available
(e.g., TDK-SA, Maxell UDXL-II, etc.). It yields high output, low
noise, and extended high frequency response. While other
tapes will function in the Model 250, performance will be
degraded (the noise floor will be higher, maximum record
levels may be lower, and frequency response may be
uneven).
We recommend using only C-60 or C-90 cassettes which
normally run 30 and 45 minutes a side, respectively. Since
the Model 250 runs twice speed, and the tapes cannot be
turned over, the usable time is 1/4 that suggested by the tape
label, as shown on the following chart.
Cassette
length
Running time in
standard recorder
at 1-7/8 ips
Running time In Model 250
at nominal 3-3/4 Ips
(Pitch control centered)
CTio 15 minutes per side,
30 minutes total.
7-1/2 minutes
C-45
22.5 minutes per side,
45 minutes total.
11-1/4 minutes
C-60 30 minutes per side,
60 minutes total.
15 minutes
C-90 45 minutes per side,
90 minutes total.
22-1/2 minutes
C-120
60 minutes per side,
120 minutes total.
NOT RECOMMENDED FOR
USE WITH Model 250
If the running times seem short, remember these are master
tapes; one side of an LP album seldom runs more than 22-1/2
minutes. Longer recordings can be built up during the remix,
if desired, working from several Model 250 master tapes.
C-120 cassettes are not recommended because they use a
thinner tape backing (1/2 mil), and the many record/play
operations necessary to create a master tape will tend to
wear out or jam the more delicate tape. (Is it worth risking the
hours of work spent creating a tape only to have it break,
wear or jam in the final stages?) Use only premium quality
C-90 or shorter tapes to be safe.
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