Audible Illusions L3A Line Preamplifier

An All-Time Classic Still Going Strong

Equipment report
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Solid-state preamplifiers
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Audible Illusions L3A
Audible Illusions L3A Line Preamplifier

I was pleased to see that the L3A features a remote volume control, a motorized Alps pot. My enthusiasm was a bit dampened when I realized that this pot is a master control that feeds the traditional, Modulus-style, left- and right-channel stepped attenuators. In effect, the signal goes through two volume controls before getting to the grid of the triode gain stage. Since the stepped attenuators are used to control both channel balance and volume, the user manual suggests setting the stepped attenuators at the 12 o’clock position as a starting point, but don’t be afraid to experiment in this regard. Input from a low-gain phonostage may require nudging the attenuator settings to 2 or 3 o’clock. In general, I found it sonically best to fine-tune the sound by setting the stepped attenuators higher and cutting back on the master control level.

Serious auditions commenced after a proper break-in period. To say that I was surprised by the musicality of the L3A would be an understatement. I don’t think that the engineer in me expected what is after all a “plain vanilla” audio circuit to sing so beautifully. Of course, it is probably a common misconception to prime oneself to anticipate great sound only from complex new circuits. Art related the following true story, which describes my reaction as well. “Back in the mid-1980s my friend Joe Grado traded me one of his tonearms and cartridges for a Modulus. He fell in love with it. Trying to understand how it worked, he takes it out to Sea Cliff and puts it on Sid Smith’s bench. He then calls me saying, ‘Art do you know what you’ve done? This linestage is wonderful! You’re going to sell thousands! But a word of caution; somehow you managed to capture the little Music Man in the design. Don’t ever lose him.’ That was great advice and I’ve tried very hard not to lose the little Music Man.”

 What captured my attention first was the precision with which the L3A enunciated transients. Both the leading and trailing edges were superbly delineated. As you can imagine, the payoff was exemplary clarity. A spectacularly lucid midrange aided in resolution of low-level detail. It felt as though a high-power microscope was focused on the inner layers of the soundstage. Complex passages were resolved without any veiling. Solid-state preamps can do this as well, but none that I’ve auditioned can fully sculpt image outlines the way the L3A does, or erect a spacious soundstage with the same conviction. In these respects, the L3A clearly and proudly displayed its tube heritage. The sonic character was slightly warm, but it never strayed far from tonal neutrality. As a result, timbral fidelity was superb. Harmonic textures were free from the gratuitous brightness or treble brashness that wreaks havoc with the reproduction of violin overtones or the upper registers of soprano voice. Much of the credit for this level of purity must go to the Russian 6H23n-EB.

The L3A never sounded inherently romantic or as colorful as a vintage tube preamp. Neither did it project that big tone sound that some 6SN7-based designs are capable of. It therefore begs the following question: Is it possible for a tube preamp to sound musically gorgeous without being overtly euphonic? The L3A made it perfectly clear that this is definitely possible. Any preamp that can caress musical lines with velvet gloves and convey the natural ebb and flow of harmonic textures is a winner in my book. Let’s talk about the frequency extremes. There was nothing to complain about in the bass range. Bass reach and pitch definition were terrific, limited only by the performance of the associated power amplifier and loudspeaker coupling. The treble range initially sounded a bit polite, lacking in air if you will. That was before I switched off the 100pF polystyrene cathode bypass caps (the Black Gate bypass caps are fixed and cannot be removed from the circuit). Art explained that these caps provide a means of voicing the preamp’s treble range to suit one’s listening tastes or system requirements. After the initial break-in period, AI advises the owner to remove the top cover and access the four red switches located at the rear of the PCB and switch all of them to the Off position. Doing so helped noticeably in opening up the treble range. However, apparently many owners prefer the sound with the switches in the On position, which would certainly make sense in the context of taming either a bright front end or hot-sounding speakers.

One of the most difficult attributes to gauge is macrodynamics, the ability of a particular component to convincingly scale the range from loud to very loud. Loudness after all is a perceptual quantity, the relationship between sound pressure level (i.e., intensity) and loudness being nonlinear. Except at very low intensities, the auditory system responds in a logarithmic fashion; a factor of two increase in loudness requires roughly a factor of 10 increase in intensity. Of course, spectral content is also a major perceptual factor as can be seen from a study of the Fletcher-Munson equal loudness curves. With these caveats in mind, it seems obvious that judgment calls in this regard carry a large margin of error. Still, I’m confident in declaring that, as far as macrodynamics are concerned, the L3A fell short of a perfect 10. It didn’t equal the dynamics of the much more expensive Pass Labs XP-30 line preamp or match the explosive dynamics of the inexpensive Berning microZOTL2.0 personal amplifier used as a line preamp. The situation was much different when it came to microdynamics. Nuances essential for fully fleshing out the music’s passion were reproduced in compelling fashion.

The L3A line preamp distills the best attributes of modern tube sound: swift transients, a detailed presentation, and natural yet non-euphonic textures. It is its insistence on the sonic truth that defines it as a true reference line preamp. The L3A’s ability to retrieve the music’s rhythmic drive and drama make it one of the most sonically persuasive line preamps on the market and one of the best I’ve auditioned over the years at any price. If your goal is to conjure up audible illusions on a grand scale, this is your preamp!

SPECS & PRICING

Gain: 30dB line out; 0dB tape & surround-sound processor outputs
Distortion: 0.10% at 1.5V, 20Hz–20kHz into 50k ohms
Frequency response: 2Hz–100kHz, +/-1dB, 
Signal-to-noise ratio: 90dB below 1.5V
Max input: 9V at 1% THD.
Signal phase: Main out, inverting; tape and s-s processor, non-inverting
Input impedance: 50k ohms, all inputs
Output impedance: Main, 1.2k ohms; tape, s-s processor, 150 ohms
Dimensions: Main chassis, 19" x 3.5" x 17"; power supply, 6" x 5" x 10"
Weight: 19.5 lbs.
Price: $3995


AUDIBLE ILLUSIONS
P.O. Box 2537
Daytona Beach, FL 32115
audibleillusions.com

Associated Equipment
Analysis Audio Omega and Basszilla Platinum Edition DIY loudspeakers; VTL Manley reference series 100/200 and First Watt SIT-1 monoblock amplifiers, First Watt F7, Futterman H3, and Atma-Sphere S-30 stereo amplifiers; Kuzma Stabi Reference, Technics SL-10, Revox B795, and Sony PS-X600 turntables; MacBook Pro laptop running Amarra V3.03 software, April Music Eximus DP1 DAC; ModWright modified Sony XA-5400ES SACD player: FMS Nexus-2, Wire World, and Kimber KCAG interconnects; Kimber KCAG speaker cable; Monarchy Audio AC-Regenerator; Sound Application power line conditioners 

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