Preamplifier - Audio Research
Influenced by some of our classic groundbreaking SP preamplifiers, the SP20 takes visual cues from past
Audio Research products while incorporating our latest designs and technologies. The SP20 is a fullfunction line stage which incorporates a phono preamplifier and, for the first time ever on an Audio
Research preamp, there is a ¼” headphone jack. Front panel controls have been minimized to two rotary
controls and an interactive touch screen display, along with power, mute and output selector buttons.
The interactive touchscreen has been designed to take full advantage of the feature set the SP20 offers, and
operation is intuitive and easy-to-use. Numerous adjustments allows customization to the performance
and display of the SP20 for seamless system integration, including input naming and gain offsets, volume
presets, and tube hours. System checks have been put into place to alert when tubes have exceeded
standard serviceable hours (4,000), and a low line auto mute function engages in the event of a power
The SP20 is fully balanced, pure Class-A with zero feedback. There are seven levels of voltage regulation,
a large power supply, and a very low-noise R-core power transformer. Both the line and phono stages
feature low-noise JFET inputs and 6H30 (2 per section) outputs. The latest high performance coupling and
bypass capacitors are used in both stages. Both the line stage and phono preamplifier offer extraordinary
frequency response and low noise. The phono section provides 58dB of gain, so the SP20 can be used with a
wide variety of phono cartridges, including moderately low output moving coils.
The headphone output is no mere afterthought; it is a low-distortion, high-performance vacuum-tube
headphone amplifier designed to comfortably drive a wide impedance range of headphones. The button
next to the headphone jack switches off the main (amplifier) outputs for headphone listening, or it switches
off the headphone jack for speaker listening.
Frequency Response:
Line: ± 0.3dB 2 Hz to 80 kHz; -3dB 0.8Hz to 220 kHz
Phono: ± 0.1dB of RIAA 10Hz to 20kHz; ± 0.4dB 5Hz to
Headphone: ± 0.05dB 20Hz to 20kHz; -3dB 0.8Hz to
Line: < .003% at 2V RMS, Bal output
Phono: < .005% at 3V RMS output, to Record output
Headphone: < .009% at 1V RMS output
Line: 13.8dB, Processor: 0dB
Phono: 58dB @ 1KHz to Record output
Headphone: 11.3dB
Line: <-101dBV volume at max.
Phono: < -77dBV to Record output
Headphone: < -88dBV volume at max.
Channel Separation:
Line: > 105dB Balanced output
Phono: > 76dB to Record output
Headphone: > 62dB
Signal to Noise Ratio:
Line: > 125dB Balanced output
Phono: > 94dB to Record output
Headphone: > 110dB
Rated Outputs: Line: 2V RMS (1V RMS SE) into 200k ohms balanced
load (maximum balanced output capability is 18V RMS at less than .5% THD+N at 1kHz.)
Phono: 0.5V RMS into 100k load at Record output
(maximum output capability is 25V RMS)
Headphone: 6V RMS maximum into 30 to 300 ohm load.
Input Impedance: 120k ohms Balanced, 60k ohms SE; Phono
impedance programmable (100, 200, 500, 1000 or 47k ohms
w/200pf unbalanced).
Output Impedance: 500 ohms Balanced, 250 ohms SE; 1000 ohms
Record Out SE; <.05 ohms Headphone SE.
Output Polarity: Non-inverting.
Maximum Input: Line: 19V RMS Balanced, 9V RMS SE. Phono:
12.5mV RMS at 1kHz.
Controls: Rotary Volume (104 steps), Rotary Input selector. Push
Buttons: Power, Mute, SPKR Off. Interactive Touch Screen. Rear RS232 control and Remote IR input.
Power Supplies: Electronically regulated low and high voltage
supplies. Automatic 30 sec. warm-up/brown-out mute. Line
regulation better than .01%.
Tube Complement: 4 6H30 dual triode.
Power Requirements: 100-125VAC 60Hz (200-250VAC 50/60Hz) 77
watts maximum. Standby 2.7 watts.
Dimensions: Width 19” (48 cm)
Height 5.25”(13.4 cm) (standard rack panel)
Depth 16.5”(42 cm) D.
Weight: 17.8 lbs. (7.4 kg) Net; 27.8 lbs. (10.5 kg) Shipping.
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