Audio Research

As a result of the ever-increasing demand by dealers and distributors for a full-function preamplifier with a level of performance comparable to their best LS and PH series preamplifiers, Audio Research has released the striking new SP20 vacuum-tube preamplifier at $9000.

The look and sonics are reminiscent of classic Audio Research components, but have been updated to reflect current aesthetics and state-of-the-art circuit concepts. The front panel has a new 4.3-inch LCD touch screen and two large rotary knobs on either side. For the first time ever on an Audio Research preamplifier, there is a ¼ -inch headphone jack which is accompanied by three buttons for Power, Mute, and Speaker off. The volume control knob rotates fully, is optically coupled, and is speed sensitive. Turn it slowly and the volume will change by small amounts. A quick turn one way or the other will raise or lower the volume by a large amount. Through the touch screen, one can change Inputs, select Stereo or Mono, Mute, adjust phase, adjust left-right Balance, and adjust the phono input Load. Through a Settings menu, the user can change input names, adjust gain sensitivity for each input, change volume presets, adjust display brightness all the way to off, and check/reset the Tube Hours counter. In addition to the Phono input, there are four other single-ended inputs, two balanced inputs, separate monitor-in and record-out, and two pairs of balanced outputs. There are also an RS-232 port, IR-input, 12V trigger, and a 15A IEC connector. Also, one of the single-ended inputs can be configured as a home theater pass-through.

The SP20 is fully balanced, is pure Class-A and has 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 outputs. The latest high performance coupling and bypass capacitors are used in both stages. Bandwidth is extraordinary, and the gain of the phono section is 58dB, allowing for compatibility with a wide variety of phono cartridges, including moderately low output moving coils. The headphone output is a low-distortion, high-performance vacuum-tube headphone amplifier designed to drive headphones with a wide range of impedances. 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.

All of these physical attributes house a preamplifier that is sonically delightful. The presentation is relaxed and natural and is transparent and solid with great dynamics and impact. Sonic images have texture and a luminous 3-D quality. The SP20 delivers just what you'd expect from an Audio Research product and does so with an ability to drive your tube or solid-state amplifier effortlessly.