Review: Luminous Audio AXIOM II Walker Mod Preamp

This review continues my trend for this year of featuring lesser-known audio companies that represent high value. Allow me to introduce you to Luminous Audio Technology, a small American company owned by Tim Stinson and based in Virginia.  In addition to their line of passive line stages, Luminous Audio offers some very fine audio cables, and a phono preamp called the Arion MkII.

In my recent review of the Pure Audio Project Trio 15 Classic loudspeakers I mentioned that at AXPONA, I noticed the Luminous Audio AXIOM II Walker Mod passive preamp and the Pass Labs XA-160.8 monoblocks were driving the speakers in the Pure Audio Project room. I was quite taken with the sound at the show. Preparing for the speaker review, I contacted Tim at Luminous Audio and asked if I could get an AXIOM II Walker Mod Passive Preamp with Remote to use.

My Memories of Passive Line Stages

A funny thing happened during the speaker review. The AXIOM II brought back a flood of memories. You see, this is not my first rodeo with a passive line stage. Hearing the AXIOM II Walker Mod in my system brought back memories of earlier passive line stages I have had over my audio career. My “gateway” passive was the PS Audio IV preamp in the early ‘80s. It could be run in active or passive mode. Next up was the Mod Squad Line stage, the Adcom GFP 750, followed by others. I asked Tim if I could hold on to the preamp to do a separate review of it.

After about a 20-year break from passive line stages, I have circled back in the last year or two with renewed interest. New products using LDR (light dependent resistor), photocouplers, and transformer-based passive preamps from the likes of Tortuga Audio, The Horn Shoppe, Icon and many others are surfacing. They have rekindled my interest in this area along with buffered unity gain preamps like the new Denafrips Athena.

About the AXIOM II

This review focuses on Luminous Audio’s top-of-the-line passive preamp called the AXIOM II Walker Mod with remote. I call it “top of the line” because Luminous offers the AXIOM II in several different configurations starting at $195. They are as follows:

  1. Axiom II RCA standard version at $195
  2. Axiom II XLR standard version at $295
  3. Axiom II Walker Mod version at $499
  4. Axiom II Walker Mod with remote at $849

So, what’s the difference in these versions. The standard version uses an Alps “blue pot” volume control. The Axiom II Walker Mod version takes the volume control to a higher level using a custom silver-plated contact 32-step Khozmo Shunt Attenuator with Vishay discrete resistors. The AXIOM II Walker Remote version to a uses a Khozmo 64-step, relay-based ladder attenuator with custom taper and an optical encoder. It has a fixed input impedance of 10K. The volume control is powered by a 5-volt wall wart that is supplied with the unit.

64-step relay-based attenuator

Common to all of the “Walker Mod” versions are premium gold over copper Vampire Wire CM-2F connectors, 6/9’s OFC copper wiring, silver contact source selector, internal damping and Luminous Audio’s own Sorbothane Isolation Feet. You choose the number of inputs and outputs and the type of resistors used. Your choices will impact the price of the unit.

The AXIOM II is quite nicely finished and has a very substantial feel for its size. Its black anodized enclosure measures 6.6 inches wide, 2.8 inches high and 7.7 inches deep. This includes the RCA connectors and control knobs. The enclosure’s finish and construction are very high quality.

Remotely Speaking

I don’t often comment on remote controls. Frankly, most of them seem to be an afterthought by manufacturers. However, this remote is one of the nicest that I have had in my hands in quite some time. The metal construction offers a substantial feel. It offers five functions, On/Off, Vol+ Vol-, Display illumination level (5 settings), and Mute. It is simple but functional and just the right size.

Many remotes I try are too large or are overly complex. They often require you to look down at the remote to press the correct button. It may seem like a small thing, but looking down to operate a remote control breaks the “listening moment” for me.

It’s Not a “One Size Fits All” Sound

This is not a “one size fits all” passive preamp and that is very important because matching the components connected to any passive preamp has a large impact on the sound. To this end, Tim customizes the unit for your electronics and speaker sensitivity.

When you order an AXIOM II, you answer a series of questions that cover things like your source output impedance, your amplifier’s input impedance, gain and sensitivity, and your speaker efficiency. This enables Tim to fine-tune your AXIOM II for your system. I applaud Tim for this extra step. And by the way, if you change a significant component in your system Tim will recalibrate your unit. He charges $35.00 for that plus return shipping. Pretty sweet!

One last note….. Remember any passive preamp does its best with low capacitance interconnects between the components. You want to be sure you are using cables that fall into this category.

Preamps and Coloration

The seductiveness of well-designed passive line stages lies in their low distortion and coloration, excellent transparency, and total lack of grain. In these areas, the AXIOM II Walker Mod did not disappoint. More than likely, your current preamp adds colorations to your system. If you ever want to hear what colorations your current preamp is adding to your system, get your hands on a good passive preamp and try it in your system. It will educate you in these areas.

The AXIOM II Walker Mod impressed me with how close the overall presentation was to my reference preamp. Note, my Denafrips Athena preamp currently costs two and a half times the price.  The AXIOM II Walker Mod throws a very large soundstage with slightly less depth than the Athena. Its tonal neutrality was on display. I did not sense any coloration being added by the AXIOM II Walker Mod. There was also no evidence of any grain or texture. That is hard to say about most preamps much less one that is under $900. Typically, preamps in this price range add or subtract from the sound. They issue you a ticket to ride on the audiophile merry-go-round of cable swapping and component changes as you chase “upgrades” to offset the coloration. That is one ride I would rather not be in the waiting line for.

Listening Notes

Curves of Life, Steve Coleman and five elements

Curves of Life is a challenging recording I often use for listening. From Steve Coleman and five elements, this album is quite well recorded with very little compression. The bass line, drums and sax are “right there”. The AXIOM II “gets out of the way” of this recording. The bass line is tightly rendered, and the sax has just the right amount of “bite”. The drums are quick, and the attack is life-like. I can’t recall a preamp under a grand that can nail this recording like the AXIOM II Walker Mod does.

Live at the Austin Outhouse, Blaze Foley

Next up, I listened to this gem of a recording that my long-time industry friend Chad Stelly turned me on to. Don’t confuse Blaze Foley’s Live at the Austin Outhouse with an “audiophile recording”. This recording is a “real” as Blaze’s songwriting, which is simple but oh so honest. If you enjoy John Prine’s writing, you may want to give this a spin.

With the AXIOM II Walker Mod in the system, the sound was virtually indistinguishable from the sound of my Athena. The AXIOM II Walker Mod does not add or editorialize in any way. It simply is “not there”. You can’t ask for anything more than that in a preamp.

You’re My Thrill, Shirley Horn

Dynamic expression was the one area where the AXIOM II Walker Mod yielded to the Athena.  While the overall dynamic expression of the AXIOM II Walker Mod was the best I have heard to date from a purely passive preamp, I must note that the Denafrips Athena, at 2.5x the price, did exhibit better microdynamics.

The AXIOM II Walker Mod treated macrodynamics very well, but the microdynamics were slightly less engaging and communicative. This impacted the “toe-tapping” factor of Pace, Rhythm, and Timing. The Athena outpaced the Axiom II on the excellent Shirley Horn You’re My Thrill album. There is a lot of subtle information on this album, and while the AXIOM II captured it all, it had a bit less dynamic inflection and engagement.

Now this may be an issue for some listeners whose top priority is dynamic expression. For most people, the gross colorations introduced by lesser preamps will have a much larger negative impact on the sound of their system. I feel compelled to point out that while I am contrasting the AXIOM II Walker Mod to the more costly Athena (perhaps unfairly), it only speaks to the respect the Axiom II has earned in my eyes.

Wrapping It Up

Be aware that passive preamps are not for everyone and are quite system dependent. But, if you find one that “locks in” your system, it will be hard to beat at any price. They are worth investigating.

If you do some quick math and simply add up the cost of the parts used in the AXIOM II Walker Mod Remote Passive Preamp, then toss in the metalwork/stenciling and add the labor to assemble the Axiom, it quickly becomes obvious that this is one hell of a deal both in terms of value and most importantly, in performance.

With the AXIOM II, you have one less colored component to try to “synergistically” match with your system. It will be added to my short list of “go-to recommendations” for friends and family that ask for component advice in this price range. I can feel very comfortable that the AXIOM II will be a “conveyer of the truth.”

If you do decide to go down the passive preamp road, I can’t think of a better place to start than with one of the Luminous Audio AXIOM II models. Nicely done, Tim!

Specifications: Axiom II Walker MOD Remote Version – $ 849.00

Length: 7.5” (including connectors and controls)
Width: 6.6”
Height: 2.8” (including feet)
Net Weight: 2.5 lbs.
Shipping Weight: 3.5 lbs.
Inputs: 1, 2, or 3 pairs RCA ( Balanced available)
Outputs: 1 pair RCA (ADDITIONAL outputs optional)
Switching type: 64-step MBB (Make Before Break)
Shaft diameter: 6 mm
Voltage: 5V/1A
Remote control with functions: Vol+, Vol-, Mute, Display (5 settings + off)

Review System:

I auditioned the AXIOM II Walker Mod preamp in my main system between my Denafrips Terminator Plus DAC and the PS Audio M1200 MonoBlocks. It replaced my Denafrips ATHENA PREAMP. The source was the new PS Audio PWT SACD transport.

Cabling for this review was from Triode Wire Labs. The speakers used for this review were the Acoustic Zen Crescendo II.

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