Audio Research LS28 All Tube Preamp - Complete with Warranty

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Like new, complete, not a blemish anywhere to be seen.

This listing is for a full package deal including the original box, manual, remote, and power cable - just like it came from the factory.

And the manufacturer warranty is valid through September of 2022!

And if you're not familiar with the LS28, we've selected a portion of a review from enjoythemusic.com that provides an excellent overview.

“The LS28 vacuum tube line stage measures 6.5" x 19" x 13.7" (H x W x D) and weighs 15.9 pounds. Styling is comparable to past ARC products with a silver chassis and a silver face plate with a black center panel which contains the green florescent display. A black anodized finish is optional. Two rotary knobs flank the front panel but unlike previous products, the left knob selects the eight inputs and the right knob controls the volume through an impressive 103-step microprocessor. Directly below the display are six push buttons labeled Power, Menu, Enter, Mono, Invert and Mute. The solidly built remote mirrors all of the front panel functions.

The Menu Function allows the user to adjust the various features of the LS28. Using the front panel buttons and the rotary dial, the settings can easily be changed. As noted above, these functions may also be changed from the remote. The features are "Auto Shutdown", "Processor Mode", "Tube Hours", "Display Brightness", "Volume Reset" and "Input Naming". The "Auto Shutdown" feature is designed to turn the pre-amplifier off after a period of inactivity. It can be set for one to eight hours or it may be deactivated. "Processor Mode" is a fairly common feature on pre-amps today. "Tube Hours" displays the accumulated hours that the LS28 has been powered on providing an instantaneous reading of the number of hours on the tubes. "Display Brightness" offers six different settings, including off for the florescent display. "Volume Reset" tells the LS28 to either remember the volume settings for each individual input or to reset them to zero after powering the unit off. "Input Naming" provides a selection of names that can be assigned to each input allowing for easier identification of the various outputs.

The rear panel is nicely laid out and everything is clearly labeled. There are eight pairs of inputs on the LS28 four of which are balanced and four which are single ended. The input impedance is 100 kOhms balanced or 50 kOhms unbalanced. There are two pairs of XLR balanced / RCA single ended outputs that are wired in parallel with an output impedance of 600 Ohms balanced or 300 Ohms unbalanced. Using both inputs simultaneously requires the use of an amplifier with an input impedance of 20 kOhms or higher. ARC also provides one set of balanced and single ended outputs to connect the LS-28 to a recorder. This output provides a fixed-level signal to which ever set of inputs are selected. The rear panel also provides an RS-232 input, an IR input, which utilizes a standard 1/8" mono connector and a 12 Volts DC trigger. Rounding out the rear panel is a power connector and a fuse holder.

The LS28 is a pure Class A design with a single gain stage and zero feedback. The analog circuitry is differentially balanced and is a hybrid design that utilizes JFETs and four 6H30 vacuum tubes with an estimated life of 4000 hours. The circuit does not invert phase. The power supply, which is fully regulated takes up half of the chassis. Audio Research lists the LS-28's frequency response at +0/-3dB, 0.04Hz to 200kHz at its rated output (Balanced, 200k Ohms load) with distortion of less than 0.007% at 2 Volts RMS through the balanced outputs.”

Click here for a PDF copy of the LS28 Manual

Specifications
Frequency Response:
+0-3dB, 0.4Hz to 200kHz at rated output (Balanced, 200k ohms load).

THD + noise:
Less than .007% at 2V RMS BAL output.

Dynamic Range:
>122 dB (AES17)

Gain:
Main output: 18.5dB Balanced output, 12.5dB SE output. Record out: 0dB (Processor input: 0dB BAL output).

Input Impedance:
100K ohms Balanced, 50K ohms SE. Inputs: 4 balanced, 4 single-ended. Assignable processor passthrough.

Output Impedance:
600 ohms Balanced, 300 ohms SE Main (2). 20K ohms minimum load and 2000pF maximum capacitance. Outputs (3): 2 main, 1
record out (XLR and RCA connectors).

Output Polarity:
Non-inverting.

Maximum Input:
16V RMS BAL, 8V RMS SE.

Rated Outputs:
2V RMS (1V RMS SE) into 200K ohm balanced load (maximum balanced output capability is 17V RMS at less than 0.5% THD at
1kHz).

Crosstalk:
-105dB or better at 1kHz.

Controls:
Rotary encoders: Volume (103 steps), Select Input. Push Buttons: Power, Menu, Enter, Mono, Invert, Mute.

Power Supplies:
Electronically regulated low and high voltage supplies. Automatic 45 sec. warm-up/ brown-out mute. Line regulation better
than .01%.

Noise:
Less than -100 dBv at maximum volume (103).

Tube Complement:
(4)-6H30P dual triodes.

Power Requirements:
100-125VAC 60Hz (200-250VAC 50/60Hz) 130 watts. Standby: 2 watts.

Dimensions:
Width Height Depth
19” (48 cm) 6.5” (13.7 cm) 13.7” (34.8 cm)
Handles extend 1.6” (4 cm) forward of the front panel.

Weight:
15.9 lbs. (7.2 kg) Net; 24 lbs. (10.9 kg) Shipping.

Please click here for detailed specifics regarding our specialized packing process that separates us from the rest.