Audio
Research SP-6 High Definition music
stereo preamplifier features:
Close
tolerance segmented gain control; 2 dB steps (guaranteed, 1½ dB tracking, ½ dB typical)
Front panel
"mute" switch for repeat settings, interruptions, etc.
Rear panel
gain "range" switch (+10 dB) for high efficiency speakers, high
output cartridges, etc.
Special
"off-chassis" construction, with all inputs/outputs isolated form
chassis, plus circuit filters to eliminate or minimize "RFI",
"TVI", and "CB" interference.
Rear panel
provision to disconnect "common" from chassis so that rack mount
installations with power amplifiers, etc., may be accomplished without
ground-loop induced hum
Separate
on-off switch and indicator for amplifier (etc.) power receptacles (3), relay
controlled, 1600 watt capacity.
Front and
rear panels are of two-color anodized aluminum construction for permanent
finish
Industrial
grade components and construction for long service life. Rated for continuous
commercial service.
With the
introduction of power amplifiers such as the D-52, D-110 and D-350, and the
availability of a number of brands of high performance speaker systems, the
need for a new and higher level of preamplifier performance for the best
systems has occurred.
After a
significant amount of research and study , we have determined that from a
cost-effectiveness standpoint, once again, the vacuum tube must be used.
We then felt
that if such a project were to be undertaken, it would be desirable to execute
it to the highest standards reasonable, recognizing that in all probability it
would be the last significant vacuum tube product offered to the music world.
One of the
expensive (and little recognized) requirements for such a concept would be a
power supply capable of providing isolated and regulated voltages to each
circuit section. This has been accomplished in the SP-6 by utilizing an all
solid state triple section regulator with massive "filtering" at the
output of each section.
With such a
power supply available, it now becomes possible to increase the bandwidth of an
AC coupled vacuum tube design without compromising the all important circuit
stability. We have done this, drawing upon the Sp-3 basic circuit design.
Increased interstage time constans, larger output coupling capacitors, and
"DC concept" feedback circuit innovations, all combine with the new
power supply to provide a new standard of sound reproduction.
Only high
quality turntables with stable pickup arms and cartridges should be used with
this preamplifier.
We suggest
that this preamplifier will provide the state-of-the-art. Reference well into
the '80s. We further suggest that inclusion of this unit in any otherwise good
music reproducing system will effect more improvement than any other single
component change.
Specifications
Frequency
Response:
High
level Section : ± .25 dB, 10 Hz to 30 kHz, -3 dB points approx. 1hz and 250 kHz
into hi-Z load. (-3 dB point approx. 1 Hz into 100 k Ω load)
Magnetic
Phono : ±1 dB of RIAA from 30 Hz to 15 kHz
Harmonic
Distortion: less than .03% at 5 volts
RMS output, IHF load, 20 Hz to 20 kHz (typically about .003% in midband)
Intermodulation
Distortion: less than .008% at 5 volts
RMS output, IHF load, SMPTE method
Gain:
Magnetic
Phono Input to Tape Output : 34 dB
Magnetic
Phono Input to Main Output : 60 dB
High Level
Input to Tape Output : 0 dB
High Level
Inputs to Main Output : 26 dB
Input
Impedance: 50 k Ω , all inputs (Magnetic phono may have any value from 10 Ω to 100k Ω subsituted. Also has provision to add input capacitance for matching
certain magnetic cartridges)
Output
Impedance: 500 Ω at 1 kHz, rising to 2,1k Ω
at 20 Hz , all outputs (recommended minimum load for maximum audio quality, 20
k Ω)
Maximum
Inputs:
Magnetic
Phono : 700 mV at 1 kHz (.2 volts RMS, 100 kHz)
High Level
Inputs : esentially overload proof.
Rated
Outputs: 5 volts RMS 20 Hz to 30 kHz,
all outputs, IHF load. (Main
output capability is 60 volts RMS output at < 1% THD at 1 kHz into 100 k
Ω load with 3 volts RMS high level input)
High Level
Noise:
250 uV RMS
max. Residual unweighted wide-band noise at main output with gain control
minimum (86 dB below 5 volts RMS output)
More than 90
dB below 1 volt RMS input (less than 20 uV equivalent input noise)
Magnetic
Phono Noise: 5 uV equivalent input
noise, wide-band RMS (-66 dB reference 10 mV input)
Tube
Complement: 6 premium grade ECC 83/12AX7
Power
Requirements: 105 -120 / 210 - 240 V AC,
50/60 Hz,
Power
Consumption: 35 watts
Dimensions
(W x H x D): 480 x 134 x 260 mm
(19" x 5¼" x 10¼")
Handles
extend : 41 mm (1-5/8") forward of front panel
Rear Chassis
fittings extend : 23 mm (7/8")
Weight: 10 kg (22 lbs) net