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.
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.
Technical 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.
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.
