audio research
SP-8

Description
Tube stereo preamplifier.

Introduced
1981

Discontinued
1988

Revisions
SP-8 Rev 1
SP-8 Rev 2
SP-8 Rev 3
SP-8 Rev 4 (1983)
SP-8 Rev 5 (1983)
SP-8 Rev 6
SP-8 Rev 7 (1985)

Rev 1 - Rev 3 are sometimes called MKI.
Rev 4 - Rev 7 are sometimes called MKII.

Options
Wood cabinet (WC-4)

MSRP (US new retail)
SP-8 Rev1: $1,495. Later increased to $1,595.
SP-8 Rev5: $1,795.
SP-8 Rev7: $1,895.

Specifications

SP-8 MKII:

Frequency response High level section: ±.25dB, 5Hz to 30kHz. -3dB points below 1Hz and above 100kHz
Magnetic phono: ±.25dB of RIAA, 30Hz to 40kHz
Distortion (THD) Harmonic distortion: Less than .01% at 2V RMS output, 20Hz to 20kHz (Typically less than .0005% in midband)
Intermodulation distortion: Less than .002% at 2V RMS output
Noise & hum High level: (1) 250µV RMS maximum residual unweighted wideband noise at main output with gain control minimum (86dB below 5V RMS output) (2) More than 90dB below 1V RMS input (less than 20µV equivalent input noise)
Magnetic phono: 5µV equivalent input noise, wideband RMS (-66dB reference 10mV input) (Approximately 1µV above 200Hz or -80dB reference 10mV input)
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 to the 40pF input capacitance for matching certain magnetic cartridges.)
Output impedance 1000 ohms main output and tape output. Recommended minimum load for maximum audio quality 20K ohms and .001µF maximum capacitance.
Output polarity  
Maximum inputs Magnetic phono, 900mV at 1kHz. (3.5V RMS, 10kHz) High level inputs essentially overload-proof.
Rated outputs 2V RMS 5Hz to 30kHz, all outputs; 60K ohm load (main output capability is 60V RMS output at ½% THD at 1kHz into 100K ohm load with 3V RMS high level input)
Power supplies Electronically-regulated supplies utilizing both vacuum tube and solid state elements. Line regulation better than .01%
Tube complement SP-8 MKI: (2) 12AX7 LN, (3) 12AX7, (2) 6922, (1) 12BH7
SP-8 MKII: (2) 12AX7 LN, (2) 12AX7, (2) 6922, (1) 12AT7, (1) 12BH7
Power requirements 100-125VAC 60Hz (190-240VAC 50Hz) 60 Watts
Other  
Dimensions 19" (48 cm) W x 5¼" (13.4 cm) H (standard rack panel) x 10¼" (26 cm) D. Handles extend 1 5/8" (4.1 cm) forward of front panel. Rear chassis fittings extend 7/8" (2.3 cm).
Weight 22 lbs. (10 kg) Net: 30 lbs. (13.75 kg) Shipping

Reviews

Number 24 (SP-8 Rev 1: Full Review)

Pictures

SP-8 MKI:

SP-8 MKII:

SP-8 Revision 5:

SP-8 Revision 6:

SP-8 Revision 7: