The LS28 line stage is a flexible and intuitive preamplifier. Four balanced and four single-ended inputs, and two sets of both balanced and single-ended outputs, allow maximum connectivity. The straightforward menu allows control of numerous parameters, including input naming, tube hours, auto shutdown, and home theater passthrough. Phase invert and mono are also standard functions. At the heart of the LS28 are four 6H30 vacuum tubes in the analog circuit. While the LS28 is the perfect match for any Audio Research amplifier, it has been designed to work with nearly any amplifier on the market today.

Since 1970, High Definition has been more than our trademark; it has been our guiding principle for all products. The Foundation Series continues this passion and philosophy, offering the listener stunning playback, great value, and unparalleled long-term support.

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.

NOISE

Less than -100dBv at max volume (103).

DYNAMIC RANGE

122dB (AES17).

CROSSTALK

-105dB

GAIN

Main output: 18.5dB balanced output. (12.5dB SE output.)  Record output: 0dB (Processor input: 0dB balanced out).

INPUT IMPEDANCE

100K ohms Balanced, 50K ohms SE. 8 Inputs – 4 balanced, 4 single-ended.

OUTPUT IMPEDANCE

600 ohms Balanced, 300 ohms SE Main (2), 20K ohms minimum load and 2000pF maximum capacitance. Outputs (3): 2 Main, 1 Record (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).

CONTROLS

Rotary volume selector (103 steps) and rotary input selector. 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%.

TUBE COMPLEMENT

(4) 6H30P dual triode.

POWER REQUIREMENTS

105-125VAC 60Hz (200-250VAC 50/60Hz) 130 watts maximum.

STANDBY

2W

PH9

FREQUENCY RESPONSE

±.2 dB of RIAA, 5 Hz to 20kHz; 1 dB points below 0.3Hz and above 80 kHz.

DISTORTION

Less than .015% at 3V RMS 1kHz output.

GAIN

55 dB at 1 kHz

INPUT IMPEDANCE

Selectable loads: 47k, 1000, 500, 200, 100 Ohms.

OUTPUT IMPEDANCE

200 ohms. Recommended load 50k-100k Ohms and 100 pF. (10k Ohms 

minimum and 2000 pF maximum).

OUTPUT POLARITY

Non-inverting.

MAXIMUM INPUT

80 mV RMS at 1kHz.

RATED OUTPUTS

0.5V RMS 10 Hz to 60 kHz, into 100K ohm load (maximum balanced output 

capability is 0.46V RMS at less than 0.5% THD at 1kHz).

CONTROLS

6 Push Buttons:  Power, Menu, Option, Enter, Input, Mute.

POWER SUPPLIES

Electronically regulated low and high voltage supplies.  Automatic 2 minute 

warm-up/brown-out mute.  Line regulation better than .01%.

NOISE

>77 dB, shorted inputs.

TUBE COMPLEMENT

(3)-6H30P dual triodes, plus (1 each) 6550WE and 6H30P in power supply.

POWER REQUIREMENTS

100-125VAC 60Hz (200-250VAC 50/60Hz) 120 watts maximum. Standby: 2 

watts.

DIMENSIONS

Width: 19” (48 cm) 

Height: 6.5” (13.7 cm) 

Depth: 13.7” (34.8 cm)

Handles extend 1.6” (4 cm) forward of the front panel.

Weight:   15.4 lbs. (7 kg) Net; 23.5 lbs. (10.7 kg) Shipping.