audio research
SP-6

Description
Tube stereo preamplifier.

Introduced
1978

Discontinued
?

Revisions
SP-6A (1978)
SP-6B (1980)
SP-6B-1
SP-6C (1981)
SP-6C-1
SP-6C-1 Revised
SP-6E (1982)
SP-6F

The SP-6F is actually an SP-8 MK II! Back in the day American Sound in Toronto could not get any SP-8's to meet customer demand due to a lack of SP-8 faceplates at the time. Some creative thinking between ARC and American Sound led to a run of 20 (or so) SP-8 MK II's with SP-6 faceplates. They called it an SP-6F.

Options
-

MSRP (US new retail)
SP-6: $1,075.
SP-6A: $1,195.
SP-6B: $1,295. Later increased to $1,495.
SP-6C: $2,195.
SP-6C-1: $2,195.
SP-6E: $2,350

Specifications

Frequency response High level section: ±.25dB, 10Hz to 30kHz.
-3dB points approximately .1Hz and 250kHz into hi-Z load. (-3dB point approximately 1 Hz into 100kOhm load.)
Magnetic phono: ±1dB of RIAA from 30Hz to 15kHz.
  SP6-B:
High level section: ±.25dB, 5Hz to 30kHz.
-3dB points below 1 Hz and above 100kHz
Magnetic phono: ±.25dB of RIAA from 30Hz to 40kHz.
Distortion (THD) Harmonic distortion: Less than .03% at 5V RMS output, IHF load, 20Hz to 20kHz (typically about .003% in midband).
Intermodulation distortion: Less than .008% at 5V RMS output, IHF load, SMPTE method.
  SP6-B:
Harmonic distortion: Less than .01% at 2V RMS output, 20Hz to 20kHz (typically about .0005% in midband).
Intermodulation distortion: Less than .002% at 2V RMS output.
Noise & hum High level:
(1) 250 µv RMS maximum residual unweighted wide-band noise at main output with gain control minimum (86dB below 5V RMS output).
(2) More than 90dB below 1V RMS input (less than 20 µV equivalent input noise).
  Magnetic phono: 5 µV equivalent input noise, wideband RMS (-66dB 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 50 kOhms, all inputs. (Magnetic phono may have any value from 10 ohms to 100 kOhms substituted. Also has provision to add input capacitance for matching certain magnetic cartridges.)
Output impedance 500 ohms at 1kHz, rising to 2.1 kOhms at 20Hz, all outputs. Recommended minimum load for maximum audio quality, 20 kOhms.
  SP6-B: Less than 500 ohms main output, 1000 ohms tape output. Recommended minimum load for maximum audio quality, 50 kOhms and 250 pF maximum capacitance.
Output polarity  
Maximum inputs Magnetic phono, 700 mV at 1kHz (>2V RMS, 100kHz).
High level inputs essentially overload proof.
  SP6-B:
Magnetic phono, 500 mV at 1kHz (1.5V RMS, 10 kHz).
High level inputs essentially overload proof.
Rated outputs 5V RMS 10Hz to 30kHz, all outputs, IHF load. (Main output capability is 60V RMS output at <1% THD at 1kHz into 100 kOhm load with 3V RMS high level input.)
  SP6-B: 2V RMS 5Hz to 30kHz, all outputs, 60 ohm load. (Main output capability is 60V RMS output at .5% THD at 1kHz into a 500 kOhm load with 3V RMS high level input.)
Power supplies SP6-B: 4 electronically-regulated solid-state supplies. Frequency-compensated high voltage supplies have a total equivalent low frequency stability of greater than 3 farads of capacitance. Line regulation better than .001%.
Tube complement SP6: (2) 12AX7 LN, (4) 12AX7
SP-6C: (2) 12AX7 LN, (2) 12AX7, (2) 6922
SP-6F: (2) 12AX7 LN, (3) 12AX7, (2) 6922, (1) 12BH7
Power requirements 105-120/210-240 VAC, 50/60 Hz, 35 watts.
  SP6-B: 100-120/190-240 VAC, 50/60 Hz, 35 watts.
Other  
Dimensions 19" (48 cm) W x 5 1/4" (13.4 cm) H (standard rack panel) x 10 1/4" (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 13 (SP-6: Full Review), Number 14 (SP-6: Further Thoughts), Number 15 (SP-6A: Full Review), Number 18 (SP-6B: Full Review), Number 19 (SP-6B: Further Thoughts), Number 24 (SP-6C-1: Special Report), Number 25 (SP-6C: Further Thoughts, SP-6C-1 Revised: Special Report), Number 28 (SP-6E: Full Review)

Pictures

SP-6:

SP-6A:

SP-6B:

SP-6C:

SP-6C-1:

SP-6E:

SP-6F: