Audio Research LS22 All-Tube Preamplifier with 6 RCA & XLR Inputs

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General:
The LS22 From Audio Research is a no-nonsense great sounding tube preamplifier that's made right here in the US.

Standout features include balanced and single ended inputs, plus six tubes for the pre-stages! Having a whopping *six* XLR balanced stereo inputs is a rarity, especially on a preamp from the 1990's.

In testing we found it sounded very musical and non-fatiguing, typical of Audio Research.

Included with the LS22 is the original owners manual.

Please note: despite this having a labeled "Phono" input, this  is Line Stage only and requires a separate phono preamplifier if you want to use your turntable. 

SkyFi Cosmetic Notes:
Very light faceplate blemishes and handle marks are present. Screws have some discoloration. Overall it presents very well.

SkyFi Technical Notes:
This LS22 was originally ordered without remote control capability. Adding remote control capability was a $500 factory option at the time.

This L22 arrived with a few minor issues which we have addressed. We replaced the power cord, repaired some corroded traces, and replaced the tape monitor switch which was broken. The tubes are all Sovtek 6922 and we replaced one weak tube.

Brand Background:
Audio Research continues its dedication to unparalleled musical expression and crafting components of the highest quality and lasting value for its customers. Our long-term dedication to service is peerless in this industry (Audio Research, with few exceptions, can repair anything ever produced during its entire history). We continue to seek out new and exciting ways to make music more real and more enjoyable. More than just a name or a marketing tool, Audio Research has come to represent exceptional performance and long-term value. Experience Audio Research – experience High Definition®.

Ownership:
Single Owner

Connections:
RCA, XLR, Captive Power Cord, AC power inputs

General Sound:
Big beautiful musical sound with little fatigue.

Cosmetic Condition:
8/10 = Very Good. Excellent front faceplate, one minor flaw on chassis side or top. See our detailed rating description here.

Working Condition:
Working perfectly and tested in our lab and listening room.

Included:
Unit and Manual

Packing:
Will be packed using our highly developed in-house process and custom packing materials.Specs:
FREQUENCY RESPONSE
±.5dB, 1.5Hz to 100kHz. -3dB points below 0.1Hz and above 400kHz.

DISTORTION (THD)
Less than .010% at 2V RMS output.

NOISE & HUM
12µV RMS IHF weighted balalanced noise (104dB below 2V RMS output)

GAIN
Main output: 18.3dB Bal., 12.7dB Unbal. Tape output: 0dB.

INPUT IMPEDANCE
200K ohms balanced, 100K ohms unbalanced

OUTPUT IMPEDANCE
400 ohms balanced, 200 ohms unbalanced main (2), 20K ohms minimum load and 2000pF maximum capacitance.

MAXIMUM INPUTS
20V maximum

RATED OUTPUTS
2V RMS 1Hz to 100kHz into 100 Ohm balanced (maximum balanced output capability is 35V RMS at less than 0.5% THD at 1kHz)

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

TUBE COMPLEMENT
(8) 6922/E88CC

POWER REQUIREMENTS
100-135VAC 60Hz (200-270VAC 50/60Hz) 90 watts maximum.

OTHER
Vacuum tube audio circuit, solid-state power supply. Inputs (6): tuner, video, phono, CD, aux tape (XLR and RCA connectors). Outputs (3): 2 main, 1 tape (XLR and RCA connectors).

Dimensions:
19" (48 cm) W x 5¼" (13.4 cm) H (standard rack panel) x 11¾" (29.8 cm) D. Handles extend 1½" (3.8 cm) forward of the front panel. Rear chassis fittings extend ⅞" (2.3 cm).

Weight:
17 lbs. (7.7 kg) Net; 27 lbs. (12.3 kg) Shipping.

Approximate Age:
1995

Link to Manual:
Click Here

Recommended Cables:
Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Phono Interconnects

Kimber Kable - BALANCED XLR Connectors - Better

Kimber Kable - BALANCED XLR Connectors - Best

Testing Process:
We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

When we first power on a preamplifier we connect its RCA output to a Sencore PA81 Power Analyzer which simulates real world loading conditions and gives us an oscilloscope interface.

The first order of business is checking that the volume control works smoothly throughout its entire range with acceptable channel balance. This is accomplished by feeding a 1 KHz sine wave into one of the preamp’s line level inputs while monitoring the preamp’s output on an oscilloscope.

We then switch to a 1 KHz square wave to test the tone controls, loudness function, and filters where applicable. During this step we are watching for equal alteration of the test signal by both channels. This also helps us identify dirty controls that will need treatment.

Once the basic line stage functions are verified, we test each input individually. This is especially important for devices that use relays to select their sources. If the preamp is equipped with a phono stage we test that as well. We use an inverse RIAA filter which allows us to feed a reference test signal into the phono input with the proper RIAA equalization and level. A square wave or sine sweep is used to verify that the device’s phono stage is faithfully reproducing the RIAA curve. If the preamp under test has balanced inputs and/or outputs these are tested as well.

We finish up our bench testing with a listening test with our bench amplifier and reference speakers. During this test we check for hum or hiss that may not have shown up in earlier testing. We also check that all of the tone controls and filters perform as expected.

If the preamplifier has remote control functions these are also tested. Preamps with tube circuits or complicated power supply topologies are connected at our long term test rig for extended stress testing under real world conditions.