Aus einem damaligen US Presseartikel über die Phase Linear 4000 Vorstufe:
Since its introduction follows the
Phase Linear 700 and 400 power
amps, the 4000 pre-amp had to be
good. Consider these features:
The Peak Unlimiter
To prevent overload in recording
equipment, studios today "peak
limit" high-level explosive transients
of the source material. Incorporated
in the Phase Linear 4000 is a
highly-advanced circuit that reads
peak limiting, immediately routes
the signal through a lead network,
and restores dynamics lost in
ecording to closely approximate
e original.
The Downward Expander
Gain riding, a recording technique
used to improve low level signal to
noise on phonograph discs,
unfortunately compresses dynamic
range that would otherwise be
available. The 4000 senses when
gain riding has been used and
immediately expands the dynamics
reciprocally downward to precisely
the intended level.
The AutoCorrelator
The advanced Autocorrelation
Noise Reduction System in the
4000 makes record/tape hiss and
FM broadcast noise virtually vanish
. . . without effecting musical content
of the source material. Over-all noise
reduction is -10 dB from 20 Hz to
20 kHz. Your music comes from a
background that is silent.
Plus . . .
... the 4000 is an advanced stereo
preamp with SQ* and Phase Linear
differential logic ... its Active
Equalizer gives you a truly flat energy
distribution over the full audio
spectrum . . . completely passive,
independent. Step-Tone Controls
allow precise tailoring of the music
to your listening environment.
It is, in a word, incredible. Ask your
dealer for an audition.
PHASE LINEAR 4000 SPECIFICATIONS
Total Distortion: Less than .25%.
Typically .02%.
Total Noise: High level: 83 dB below
2 volts. Phono: 72 dB below a 10
millivolt reference.
Tone Controls: Bass: Monotonically
increasing and decreasing, dual hinge
points, ± 8 dB

20 Hz, Hinge points
switch selectable beginning at 40 Hz
or 150 Hz. Treble: Monotonically
increasing and decreasing, dual hinge
points, ± 8 dB

20 kHz. Hinge points
switch selectable beginning at 2 kHz
and 8 kHz.
Active Equalizer: 6 dB/octave boost
below 50 Hz.
Peak Unlimiter: (Nominal peak unlimit
rate attack threshold, front panel
variable) .5 dB/micro second for + 6 dB
peak unlimited operation.
Downward Expander: Downward
expansion commences at —35 dB.
Ultimate limit is —41 dB. Unlimiter
window is 35 dB wide, upper and lower
thresholds are simultaneously variable.
Auto Correlator (Noise Reduction
Systems): High frequency noise reduc-
tion commences at 2 kHz and is 3 dB,
reaching 10 dB from 4 kHz to 20 kHz.
Weighted overall noise reduction is
-10 dB from 20 Hz to 20 kHz.
Size: 19" x 7" x 10" -Weight: 18 lbs.
Warranty: Three years, parts and labor.
Maw ( f hunt 4000
THE POWERFUL DIFFERENCE
*SQ is a trademark of CBS Labs. Inc.
PHASE LINEAR CORPORATION. P.O. BOX 1335. LYNNWOOD. WASHINGTON 98036