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Audio Research SP9 MKII Tube / Solid State Hybrid Preamp With Phono Input

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Pickup currently unavailable at SkyFi 479

Audio Research Sp9 Mkii Tube /Solid State Hybrid Preamp With Phono Input Preamplifier

Audio Research SP9 MKII Tube / Solid State Hybrid Preamp With Phono Input

SkyFi 479

Pickup currently unavailable

479 South Broad Street
Glen Rock NJ 07452
United States


These ARC preamps are our best sellers.

The SP series, as opposed to the LS series, features a built-in phono preamp section for convenient connection to your turntable.

Legendary warm tones, mostly due to tube harmonics, is the signature for these preamps.

In perfect working and overall great cosmetic condition. We've only rated this a 7 for "Physical Condition" due to its age and the fact that we're super conservative.

Yes it's priced like the day it left the factory in the late 1980's, but well worth it as you're not likely to find a better sounding preamp in this price range.

Functional Notes:
• Audio research designed this preamp with several load impedances for various sources. Most notably the CD input uses 154K input resistors which results in a noticeable volume drop when using the CD input. Our thought is that ARC designed the input this way to take advantage of the increased dynamic range available on CD.
• At some point in the past these resistors were bypassed, and we returned this CD input to operate as originally designed.

This preamp does offer end-user adjustment of the phono cartridge loading. However this involves soldering a pair of precision resistors to a specific set of terminals on the underside of the main preamplifier board.

It is currently set to the stock 47K Ohm setting.

If you need this this converted to a different value to match your phono cartrridge, please let us know during your purchase and we'll take care of it.

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®.

Single Owner

RCA inputs and outputs. Captive power cord.

Cosmetic Condition:
7/10 = Good. One or two minor scratches. Well Maintained.. See our detailed rating description here.

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

Unit and box

Original Manufacturers Packing

High Level Section: ±.5dB, 5 Hz to 50 kHz, - 3dB points below 1 Hz and above 200kHz. Phono: ±.3dB of RIAA, 30Hz to 40kHz.

Less than 0.1% at 2V RMS output. (Typically less than 0.005% in midband)

High Level: (1) 70 µV RMS maximum residual unweighted wideband noise at main output with gain control minimum (98 dB below 5V RMS output). (2) More than 100dB below 1V RMS input (less than 7µV equivalent input noise). Phono: 0.12 µV equivalent input noise, IHF weighted, shorted input (78dB below 1 mV input).

Phono input to tape output: 46dB. Phono input to main output: 66dB. High level inputs to tape output: 0dB. High level inputs to main output: 20dB.

50K ohms line inputs. 40K phono (Phono provisions for any value below 47K ohms or added input capacitance for matching certain magnetic cartridges). 

500 ohms main output. 850 ohms recorder output. Recommended load 60K ohms and 100pF. (20K ohms minimum and 1000pF maximum).

Phono, 200mV at 1kHz (1000 mV RMS, 10kHz). High level inputs essentially overload proof.

2V RMS 5Hz to 50kHz, all outputs; 60K ohm load (main output capability is 50 V RMS output at 1/2% THD at 1kHz into a 100K ohm load with 5V RMS high level input)

Electronically–regulated low and high voltage supplies and electronic decoupling. Shielded toroid transformer. Line Regulation better than .01%.

(2) 6DJ8/ECC88.

100-135 VAC 60 Hz (200-270 VAC 50/60Hz) 50 watts max.

19” (48 cm) W x 5 1/4” (13.4 cm) H (standard rack panel) x 10 1/4” (26 cm) D. Handles extend 1 5/8” (4.1 cm) forward of the front panel. Rear chassis fittings extend 7/8” (2.3 cm).

20 lbs.

Approximate Age:

Link to Manual:
Click Here

Recommended Cables:

Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Phono Interconnects - Better

Kimber Kable - Flagship Phono Interconnects - 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 PCB’s 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 1KHz 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 1KHz 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.

SKU: 104516