Review: Linear Tube Audio Aero DAC Part 2 Tube Rolling

The ability to flavor the sound of our hifi by swapping tubes is a beautiful thing. After all, the perfect hifi doesn’t exist because we use ‘em to listen to music, a deeply personal thing.

Speaking of a personal thing, there is nothing more personal than tube rolling since they are very much like a tasting—whether it be wine, tequila, or hot sauce—in that the thing being tasted, not tested, appeals to our pallet, a deeply personal thing.

Before we go ahead, I recommend reading Part 1 of the LTA Aero DAC review first. I’ll wait….

I was sent a total of 5 extra sets of tubes to roll into the Linear Tube Audio Aero DAC that can roll with 6SN7s or 12SN7s with a flip of the rear panel switch.

All Aero DACs come with NOS GE 12SN7s but LTA also offers the Ray Tubes as an upgrade option directly from their site. The other NOS tubes used for this rollicking and rolling extravaganza were supplied by LTA for the purpose of this review but if you want ‘em it’s up to you to find ‘em (which is why prices are only given for the new production Ray Tubes).

The list (from left):

the stock NOS GE 12SN7s
NOS Tung-Sol JAN-12SN7GT – Round Black Plate, Oval Mica
NOS RCA JAN CRC 12SX7GT – Smoked/Grey Glass
NOS GE JAN-12SX7GT(A) – Grey Plate
Ray Tubes SELECT 6SN7 ($149.99/matched pair)
Ray Tubes RESERVE 6SN7 ($479.99/matched pair)

According to my eyes and heart, tubes are lovely things, things that remind me of a favorite quote from Haruki Murakami from his novel South of the Border, West of the Sun (albeit about LPs):

And every time, this thought hit me: It wasn’t a record she was handling. It was a fragile soul inside a glass bottle.

My process for rolling took real time and attention as the differences imparted on music was more and less subtle. Which is not to say unimportant, a distinction seemingly lost on people who are more concerned with price than a deeper connection to music.

A word on volume level matching and comparisons—I find it infinitely more important to listen over time than to perform A/B comparisons. Infinitely more important. And I don’t know about you, but when I listen to music over time I have a tendency to make it louder, less loud, and even louder still depending on the music and my mood. All to say if you think a 1dB difference in level is more important than time, we’ll have to agree to disagree (without being disagreeable).

The system used throughout was the recently reviewed Fern & Roby Amp No. 2 driving the Barn resident DeVore Fidelity O/96 (review), with the Barn resident Auralic AIRES G1.1 (review) feeding the LTA DAC via a length of AudioQuest Carbon USB cable (see full system and Barn details).

While I let each pair of tubes play all kinds of music for a few days, I let Nick Cave & the Bad Seeds new one, Wild God, serve as the nitty gritty comparator. Why this record? It’s still new to me and I really like it so I have yet to grow tired of listening to it. Of course I also used familiar ‘test tracks’, music I’ve been using to compare hifi gear in some cases for decades. But the real trick to comparative listening is relaxing—there is nothing more destructive to the pleasure we get from listening to music than clinched uptight thinking we’re performing science mode. Truth seeking in hifi is akin to looking for a garden in a morgue. For the final days, I rolled in my favorite tubes for closer in time A/B (and C) comparisons.

I initially thought I’d run down the sonic differences according to each set of tubes but decided that was silly and potentially misleading because where you stick a tube is more important than the tube. Or to put it another way, the same tube may be great in one DAC and not so great in another but ultimately taste, a deeply personal thing, picks the winner. So the following findings are what I thought of the LTA Aero DAC’s sound with my three favorite sets of tubes and is in no way a hunt for the ‘Best” tube. Or to put it even simpler still, this is not a review of tubes, it’s Part 2 of a review of the Aero DAC.

My favorite tubes to use in the LTA Aero DAC were the Tung-Sols. According to my tastes and the system in play, the Aero/Tung-Sol combination offered a nicely balanced sound overall with an added touch of richness in tone and texture and more than a touch of extra air as compared to most of the others. While the Tung-Sol in the Aero did not deliver the last word in ultimate resolution or grip, that award goes to the Ray Tubes, listening over time proved that this combination had me digging more deeply into the music that had real wow-factor, whereas some of the other tubes had me focusing on aspects of sound quality—a real meh factor.

Running a close second were the GE 12SX7GT(A) because they offered a huge presentation with tons of air and space while still delivering richness in tone and texture albeit with a level of refinement that was bit more woolly than the Tung-Sols. I found the overall balance with these GEs in the Aero DAC gave music real big drama. And I like real big drama.

The track “Conversation” from about the 4-minute mark on is some of the most soul-stirring music I’ve consumed in some time and is, to my mind, all about real big drama. I find it nearly impossible to not raise both hands high toward the sky when Cave cries out “You’re beautiful! You’re beautiful, again!” Amen to that. You may have guessed by now that I like my music rich, full, and vivid as opposed to tight, lean, and highly resolved. Guilty as charged.

In third place, although in some ways 1st, were the Ray Tubes Reserve 6SN7s. The thing that puts them in first place is resolution, bass control, and an overall tighter, cleaner sound compared to any of the NOS variety while still imparting a nice sense of tone and texture. I imagine, all things considered, that these Ray Tubes will be a good choice for people not comfortable hunting for NOS tubes, or with tubes in general, as all Ray Tubes come with a one-year warranty against any manufacturing defects. The Ray Tubes also win the sexiest shaped tubes, but that says more about me than them.

The Ray Tubes Select 6SN7s were a bit too clean for my tastes tipping music a bit toward the antiseptic while the RCA 12SX7GT had some of the qualities I enjoyed in the Tung-Sol and GE 12SX7GT(A), they resulted in a bit less richness and drama and as we know, I prefer more. Finally, getting back to the original GE’s that came with the Aero it became clear that they offer more apparent detail than the NOS tubes I preferred which emphasized that hardness I mentioned in my first review.

Summing up, the tubes I preferred—Tung-Sol 12SN7GT, GE 12SX7GT(A), Ray Tubes Reserve 6SN7—all brought out qualities that gave the LTA Aero DAC the kind of richness and rightness that suits my tastes to a T, bringing music to life in Barn and in me to a greater degree.

Linear Tube Audio Aero DAC
Price: $3950
Company Website: LTA

Features and Benefits

Pure R2R Ladder DAC: No oversampling and no digital filters
Class-A ZOTL Output Stage: The first and only DAC in the world to use ZOTL technology
Zero Negative Feedback: No global or local feedback for timbral accuracy and enhanced transient response
Isolated Power Rails: Dedicated power supplies for each section for precise electrical isolation
Advanced Protection: Circuitry to protect downstream components from tube failures
Easy Tube Swapping: Fully visible tubes and simple toggle switch for using either 6SN7 or 12SN7 output tubes
Balanced XLR Outputs: Enhanced signal quality and crystal clear audio
Three Inputs: USB, Optical, and Coax inputs for flexible connectivity
Direct-Coupled Topology: No capacitors in the signal path
Plug & Play: No drivers needed for Windows or Mac
Advanced Power Regulation: Belleson-regulated, multi-stage choke filtration for clean power
Digital Galvanic Isolation: Blocks noise from music sources entering the DAC circuit
Made in the USA: Designed and built in our Takoma Park, MD workshop