Audio Research SP-20 Preamp
Top of the line fully functional preamp just below the reference series from AR.
Fully balanced pure class-A circuit design for superb accuracy and transparency.
Awesome LCD readout which makes adjustments and status super visible, even to older eyes.
Full featured phono section allows a connection to just about any phono cartridge making this a great bargain in high end audio.
This particular unit was a floor model and is in perfect working condition. Cosmetically it’s near perfect with a tiny edge nick near the left knob, and a few surface scratches on the top.
It comes complete with all original packaging - remote, power cord, etc.
The SP20 is a fully balanced, pure class-A preamplifier that uses no overall loop negative feedback. It has seven levels of voltage regulation, and its line and phono stages each include low-noise JFET inputs and two 6H30 output tubes. The phono stage provides 58dB of gain, which makes it compatible with most low-output MC cartridges. In addition, for the first time on a preamp, ARC has included a ¼" headphone jack. Nor is the SP20's headphone amp an afterthought—it takes advantage of the SP's entire line stage by routing the output signal through an impedance buffer into the headphone jack; a switch toggles the preamp output between the headphone output and the main speaker output.
The SP20's physical appearance combines old and new. The faceplate with two large knobs evokes the look of the classic Audio Research designs of the early 1970s. There are also controls for input selection, volume, power, mute, and the headphone/speaker toggle. Unlike the ARCs of 40 years ago, the SP20 also has a touchscreen, similar to that found on the company's flagship Reference 10 line stage ($30,000). This indicates input name, monitor input, volume, stereo or mono playback, phase, load, mute, balance, and output selection, and grants access to the settings menu. You can adjust the gain of each input to maintain a uniform output level when switching inputs, and assign to each input a different name, to be displayed when the input is selected. The Display submenu lets you adjust the display's brightness and timeout. When engaged, timeout dims the screen for a specified time period until any button is pressed.
On its rear panel, the SP20 has more inputs and outputs than I've seen on any other ARC model: one single-ended phono input, five single-ended line inputs, two balanced line inputs, one single-ended line output, two balanced line outputs, and a single-ended recording loop.
I asked Audio Research's head of marketing, Dave Gordon, how he felt the SP20's phono stage compares with ARC's separate phono and line-stage models. He said that he felt the SP20's phono stage provides the same amount of gain as and is comparable in sound quality to that of the PH8 ($7000), but is a different circuit design. He thinks the sound quality of the SP20's line stage is somewhere between those of the LS17 SE ($5500) and LS27 ($7500) line stages, but has greater bandwidth (to 220kHz) than both. It struck me—if all this is true, a preamp that can provide sound quality comparable to $13,000 or $14,000 worth of ARC separates (excluding the cost of interconnects), and that has a headphone amp and a broader range of features, would be a relative bargain at $9000.