Audible Illusions Modulus 3A Tube Preamplifier with PHONO

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General:
Modulus 3A vintage tube preamp with optional and excellent built in phono stage. Features an external high-quality power supply to minimize noise and reduce heat.

Brand background:
For over forty years Audible Illusions has been recognized as a major contributor in the development of high-end audio components. Based on the design philosophy that “Simpler is Better” our Modulus preamplifiers have received critical acclaim from audio critics and enthusiastic owners the world over. Today, our resolve to bring value to reference level sound is greater than ever. To do so, we combine innovative design with the finest components available.

Ownership:
This model was previously factory reconditioned in 2001 with one owner since who traded it in.

Amplifier recommendations:
Both solid state and tube should pair well with this unit.

Connections:
7 sets of inputs including phono plus 3 sets of outputs, 2 of which are variable and one a tape output. All connections are high-quality RCA jacks.

General sound:
Warm tube sound with great harmonics and laid-back delivery.

Cosmetic condition:
We rated this a 7 with light signs of use and wear. Click here for our detailed rating descriptions.

Working condition, Technical Notes:
• All four vacuum tubes were replaced with strong testing used Sovtek 6922.
• All functions tested and working as intended
• The CD and DAT inputs have slightly lower gain than the other line level inputs by design.
• This unit uses a subtle LED backlight for the knobs which adds some glow in low lighting environments.

Included:
Preamp with external power supply and power/umbilical cables.

Packing:
Will be packed using our highly developed in-house process and custom packing materials.

Original MSRP:
$2499

Specs:
Phono section gain: 28dB at 1kHz (MM), 27dB (MC). Line section gain: 30dB. Output impedance: 1.2k ohms (main), 150 ohms (tape). Input impedance: 47k ohms. Frequency response: 2Hz-100kHz within 1dB, measured with a 1:1 probe/100k ohm load. Phono section RIAA error: 20Hz-20kHz ±0.25dB. Distortion: 0.02% (MC phono section); ±0.015% at 20kHz (MM phono section); ±0.15% at 1.5V RMS out, 20Hz-20kHz into 50k ohms, ±0.12% at 500mV RMS out, 20Hz-20kHz, into IHF load (high-level section). S/N ratio: 74dB ref. 5mV wideband input (MM phono section); 85dB ref. 1.5V RMS wideband input (high-level section).

Dimensions:
17" W by 3" H by 10" D (preamplifier); 5" W by ½" H by 10" D (power supply).

Age:
Unit was built in the late 1990's.

Reviews:
Stereophile, by the one and only Michael Fremer, 1996

Link to manual:
Audible Illusions Modulus 3A Tube Preamplifier

Recommended Cables:

Click below to add our recommended matching cables from Kimber Kable, all brand new as SkyFi is an official Kimber dealer.

Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Phono Interconnects - Better

Kimber Kable - Flagship Tonearm Interconnects - Best

Kimber Kable - Power Cords - Better

Kimber Kable - Power Cords - Best

Our 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.

If the preamplifier passes visual inspection, we move on to a full test of all of the tubes. We use an Amplitrex AT-1000 Tube Tester which is capable of testing both emission and Gm with a high degree of accuracy. We document the results of each tube and replace any weak or suspect tubes before proceeding.

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.