STATUS - SOLD
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Description :
The Audio Research SP-6A is a tube stereo preamplifier introduced in 1978 with extremely revealing and detailed phono section. Front and rear panels are of two-color anodized aluminum construction for permanent finish and lettering, made of industrial grade components and construction for long service life. The front panel of the Audio Research SP-6A includes a "mute" switch for repeat settings, interruptions, and at the back there is a gain "range" switch (-10dB) for high efficiency speakers, and high output cartridges. The special "off-chassis" construction, with all inputs/outputs isolated from chassis, plus circuit filters eliminates or minimizes "RFI", "TVI", and "CB" interference. Rear panel provision disconnects "common-mode" interference from chassis so that rack mount installations with power amplifiers, etc., may be accomplished without ground-loop induced hum. There is a separate on-off switch and an indicator for amplifier power receptacles, relay controlled and has 1600 watts capacity.

The power supply is capable of providing isolated and regulated voltages to each circuit section. This has been accomplished in the Audio Research SP-6A by utilizing an all solid state triple section regulator with massive "filtering" and energy storage 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. Increased interstage time constants, 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. It has close tolerance segmented gain control, approximately 2dB steps. Only high quality turntables with stable pickup arms and cartridges should be used with this amplifier. The Audio Research SP-6A will provide the state-of-the-art reference, and inclusion of this unit in any otherwise good music reproducing system will affect more improvement than any other single component change.

Specifications :
Frequency Response.......................High level section: +/- 0.25dB, 5Hz to 30kHz.
                               .......................-3dB points approximately 0.1Hz and 250kHz
                               .......................into hi-Z load. (-3dB point approximately 1Hz into 100k ohms load)
                               .......................Magnetic phono: +/- 0.25dB of RIAA from 15Hz to 40kHz
Harmonic Distortion..........................Less than 0.01% at 2V RMS output, IHF load, 20Hz to
                            ...........................20kHz (typically about 0.001% in midband)
Intermodulation Distortion..................Less than 0.002% at 2V RMS output, IHF load, SMPTE method
Gain...............................................Magnetic phono input to tape output, 34dB
      ................................................Magnetic phono input to main output, 60dB
      ................................................High level inputs to tape output, 0dB
      ................................................High level inputs to main output, 26dB
Input Impedance...............................50k ohms, all inputs
                        ..............................Magnetic phono may have any value from 10 ohms to
                        ..............................100k ohms substituted.
                        ..............................Also has provision to add input capacitance for matching certain
                        ..............................magnetic cartridges
Output Impedance............................500 ohms main output, 1000 ohms tape output. Recommended
                          ............................minimum load for maximum audio quality, 50k ohms and 500pF
                          ............................maximum capacitance
Maximum Inputs..............................Magnetic phono, 500mV at 1kHz (1.5V RMS, 10kHz)
                        ...............................High level inputs essentially overload proof
Rated Outputs..................................2V RMS 5Hz to 30kHz, 60k ohms load
                      .................................Main output capability is 60V RMS output at 0.5% THD at 1kHz
                      .................................into a 500k ohms load with 3V RMS high level input)
Noise..............................................High level: 250 microvolts RMS maximum residual unweighted
        ..............................................wideband noise at main output with gain control minimum
        ..............................................(86dB below 5V RMS output) More than 90dB below 1V RMS
        ..............................................input (less than 20 microvolts equivalent input noise)
        ..............................................Magnetic phono: 5 microvolts equivalent input noise, wideband RMS
        ..............................................(-66dB reference 10mV input)
Tube Complement............................6 premium grade ECC83/12AX7
Power Requirements........................105 to 120 / 210 to 240 VAC, 50/60 Hz, 35 watts
Dimensions(w x d x h)......................48.5 x 30 x 14 cm
Weight............................................8kg

Miscellaneous :
Matching.........................................Audio Research D-79 Power Amplifier
Made In...........................................USA
Condition.........................................8/10

Product Information :
http://www.arcdb.ws/SP6/SP6.html
http://www.arcdb.ws/SP6/ARC_SP6A_flyer2.jpg (Flyer)