Pioneer
SPEC-4
Stereo Power
Amplifier in “DC” Configuration with Independent Left/Right Dual Power Supplies
and Circuitry.
Think of the
Pioneer SPEC-4 Power Amplifier as two independent mono amps in one chassis. Our
stayahead reputation in hi-fi technology is upped another big step here by
achieving real independence for the essential circuits in both the left and
right channels. Physically separated signal paths and dual power transformers,
four big capacitors (two per channel) to prevent power dry-up, separate
left-right relays – everything to prevent crosstalk and distortion that erode
stereo clarity and tonal quality. Because the SPEC-4 is of Pioneer's new
generation of “DC” configuration power amps, its performance is never
compromised by capacitors in the negative feedback loop. The results; a
continous power output of 150 watts per channel, min. RMS, at 8 ohms from 20 to
20,000 Hz with no more than 0,1% total harmonic distortion.
DYNAMIC
POWER WITH ULTRA-LOW DISTORTION
Why go for a
separate component for power amplification? Pioneer's SPEC-4 clears up that
question, and your music, with indisputable proof that separate power
amplification is really worth it. Massive power reserve is available throughout
the spectrum, including the super-low and ultra-high ends. Pulsive signals –
i.e. musical signals – are reproduced with transparency and clarity at all
levels, at all times. This high quality is achieved with Pioneer's stay-ahead technology, as explained below.
STAY-AHEAD
AUDIO CIRCUITRY
the Pioneer
SPEC-4 uses the latest ciruitry for power amplification, as follows. The input
is formed by a dual PNP transistor differential amplifier , loaded by a current
mirror circuit. This is followed by a constant-current-loaded predriver and a
3-stage Darlington connected driver. The final output is in the parallel SEPP
(Single Ended Push Pull) configuration. Here are the advantages one by one:
(1) Dual
PNP Differential – Zero DC voltage is constantly maintained at the input.
(2) Current-Mirror
Loading – Reduces the load to the dufferential input to achieve a high gain
which, in turn, permits the application of sufficient negative feedback for the
effective reduction of distortion. DC stability is also improved.
(3) 3-Stage
Driver – Against loads are reduced so that the transistorsin the circuit are
called on to operate only at their most linear operating curve. Distortion is
reduced and gain is high.
(4)
Parallel SEPP – This output configuration reduces by half the amount of current
flowing through the output (power) transistors, again allowing the utilization
of only the most linear parts of their operational curves, reducing distortion
without sacrificing output.
DUAL POWER
SUPPLIES FOR LEFT AND RIGHT CHANNELS
Better
2-channel performance all around. That's the result of physically separating
the left-channel and right-channel power supplies and signal paths. Paired
power transformers are employed, one for each channel. The advantages show up
in steady-state as well as dynamic
conditions. We've even separated the power relays for the two channels. No
matter how complex the signal handled by one channel , the other is always
ready to perform independently for more musicl clarity. Think of the SPEC-4 as
two independent mono amplifiers housed in one stereo unit, both as perfect as
we can make them.
MASSIVE
POWER RESERVE
Power
dry-up? It takes an acute ear to detect it from most amps when tey are playing
ordinary music. But it shows up easily during dynamic stareo passages in rock,
classic and other music unless definite measures are taken to prevent it. The
Pioneer SPEC-4 takes those measures. Because it operates on a “DC” basis, with
no capacitors whatsoever in the negative feedback loop, and because it features
a truly dependable power supply formed of two huge power transformers and four
22,000uF filter capacitors, power dry-up is entirely avoided. Your music is
reproduced with vivid, full-power lows and natural transients for high
resolution.
LOW-IMPEDANCE
DESIGN THROUGHOUT
Impedance
plays a vry important role in amplifier design and behavior. High impedance in
the grounding and hot lines can result in significant losses of power and
increases in distortion. The SPEC-4 avoids this in the following ways:
(1) Pure
Copper Grounding - Low impedance
prevents the generation of distortion and safeguards power loss. We've achieved
it with the use of pure copper plates, 20 mm wide by 2 mm thick, in the ground
path of the dielectric capacitors.
(2) 14-Gauge
Cables – Again, low-impedance performance is assured with the use of very thick
(2,03 mm or 14 gauge) stranded cables in connecting the power output assembly
to the output terminals and throughout significant large current circuits.
Reproduction never suffers, even with large current flows are suddenly
introduced. These “coat-hanger” cables also permit the dielectric capacitors to
charge quickly and efficiently.
(3) Copper-Foil
Circuit Boards - Conventional printed
circuit boards use thin layers of copper foil. Ours use layers twice as thick –
70 u – to further reduce circuit impedance even when large current flows are
required.
PEAK-REDING
POWER METERS
The
logarthmically compressed scales of the twin power-output meters on the front
panel of the Pioneer SPEC-4 make it easy to read peak power output in both
channels accurately. No sensitivity changing is necessary when large or small
output levels are chosen. The large, outer-magnet type meters indicate the full
output peaks within 70 milliseconds, aided by an advanced detection circuit for
instant-by-instant accuracy. Their direct-readout scales indicate from 0,01
watt to 300 watts.
INDEPENDENT
LEVEL CONTROL
Also on the
froont panel are independent level controls for each channel's input. Optimum
input level sensitivity is thus easy to achieve regardless of the output of the
connected preamplifier. Each control is an attenuator with 22 stops, calibrated
precisely in 1 dB increments from 0 to -20 dB. Gang error and indication error
are minimum so that you may adjust inputs delicately and accurately.
POWER
PROTECTION
The SPEC-4
circuit for speaker and power transistor protection is formed of a quick-response power relay and a
dependable electronic detection stage. Detection of DC components and overload
currents is instant, triggering the relay and electrically disconnecting the
amplifier from your speakers and its own output stage. The protection circuit
also serves as a muting circuit which eliminates click noise otherwise heard
when you switch the power on or off we've taken extra steps to protect stereo
separation with the use of two independeny relays, one for each channel, with
twin contacts in parallel. Surge current, introduced as you switch the power
on, never reaches the large power transformer/capacitor block thanks to this
extra protection.
OTHER
FIRST-CLASS FEATURES
Rear Panel
Trminal Protection - Rear terminals are
protected from damages with a terminal protector.
Rack-Mounting
Ready - All dimensions/specifications
suitable for use in standard EIA equipment racks.
Specifcations
Circuitry: Current mirror loaded differential amplifier,
3-stage Darlington parallel push-pull, direct-coupled OCL, (DC amplifier
construction)
Power
Output: Continuous power output of 150
watts per channel min, at 8 Ω from 20
Hz to 20,000 Hz with no more than 0.01% total harmonic distortion of 180 watts
per channel at 4 Ω from 20 Hz to
20,000 Hz with no more than 0.03% total harmonic distortion.
Total
Harmonic Distortion (20 to 20,000 Hz, 8 Ω) :
No more than 0.01% (continuous rated power
output)
No more than
0.01 % (75 watts per channel power output)
No more than
0.01 % (1 watt per channel power output)
Intermodulation
Distortion (50 Hz : 7,000 Hz = 4:1, 8 Ω )
No more than
0.01 % (continuous rated power output)
No more than
0.005% (75 watts per channel power output)
No more than
0.005% (1 watt per channel power output)
Frequency
Response: 5 to 100,000 Hz, +0 dB, -1 dB
Input
Sensitivity/Impedance: 1 V/50 K Ω
Output
Speaker: 4 to 16 Ω
Damping
Factor: 100 (20 to 20,000Hz, 8 Ω )
Hum and
Noise: 115 dB (IHF, short-circuited A
network)
Semiconductors:
ICs: 2
Transistors: 61
Diodes: 62
Power
Requirements: 110/120/220/240 Volt 50/60
Hz (switchable)
Power
Consumption: 760 watts/950 VA
Dimensions
(W x H x D): 19” x 17 ¾” x 7”
Weight
: 54 lbs unpacked