VTL TT-25 Review

Review by Steve Guttenberg
Listener HiFi & Music Review
Summer 1999

Vacuum Tube Logic TT-25 Limited Edition Monoblock Amplifiers: $1500 per pair. Vacuum Tube Logic, 4774 Murrieta St., No.10, Chino, CA 91710. (909)627-5944. www.vtl.com

"HOW many watts?"

We've all heard that one thousands of times. Yeah sure, everybody knows more watts will get ya' more SPLs. But exactly how beautiful those SPLs will sound...ah, yes, that's a trickier question.

It's funny: Long before the ultra-low power single-ended triode vanguard caught the imagination of some quarters of the American audiophile community, low power push-pull amps from the likes of Audio Research, Mark Levinson, and Krell had their own mystique. The notion seemed logical: The lowest power amplifier of the line is the simplest, most straightforward example of the designer's concept. Ergo, bigger amps could be thought of as sacrificing transparency and nuance for brawn.

Mega amps retain their unquestioned hold over many audiophiles' imaginations. A fine example is Vacuum Tube Logic's own mondo-monoblock, the 1250-watt Wotan. Yup, VTL has a thing about power. But I must be weird, because I'm more interested in the tiniest VTL, the TT-25--aka Tiny Triode Monoblock. Hey, it's a brute compared to most single-ended amps: 25 watts in triode, switchable to 45 watts in tetrode. That's getting up there.

Each pair of Tiny Triodes come packed with a "Certificate of Birth." My twin review samples were "born" on 12/14/98, weighing in at a bouncy 14.5 pounds each. These palm-size beasts are adorable little things, but they sound like very grown-up amplifiers. They should: Tiny Triodes have been around for over ten years (the current generation is part of a special limited edition of 500 pairs).

VTL Tiny Triodes are made in production runs of 50 units. After the amps are assembled and tested, the VTL factory staff carefully match up pairs of the most similar sounding pieces. Each and every amp gets packed with a full set of frequency and power measurements. I hear a lot of talk on Planet High End about offering extra value, but VTL is making good on that promise by delivering these all-tube monoblocks for the less than price of most entry level stereo tube amps. VTL's President, Luke Manley, admitted his profit margins are lower on the $1500 Tiny Triodes, but he wants to entice those first-time buyers to start dreaming about Wotans. Right on, Luke.

Clearly, VTL's designs have evolved over the company's 12-year history, but their wide bandwidth circuit topology is the same as it ever was. Manley doesn't subscribe to trendy hair shirt zero-feedback dogma, so VTL incorporates a modest amount: 6 to 14 dB of global feedback, to keep the output impedance of their amplifiers at a reasonable 1.5 ohms.

The coolest feature of the Tiny Triodes is that nifty Triode/Tetrode switch. They sound quite linear in tetrode, thank you very much, but I'm a tube-o-phile so I spent most of my listening time in triode, where the high frequencies roll off a tad sooner. In practice that wasn't a problem: Whenever the Tiny Triodes veered too far over to the warm and mellow side, I toggled over to tetrode mode to get back to a more neutral balance. (VTL recommends turning the amps off for switchovers, though, to extend tube life.) So you really can have it both ways: tetrode for more detail and triode for more luscious tube sound. The differences are hardly dramatic, but certainly musically relevant.

Truth be told, the Tiny Triodes are optimized for triode operation. As Luke explained: "The plate to plate impedance of the output tubes is lower in triode, improving the interface with the output transformer." He feels the amps are more stable in triode and thus can deal with trickier loads with greater ease. BTW, the Tiny Triodes' unusual speaker output connectors accept spades or bare wire, but--yes, no bananas.

I love the way the tubes peek through that sexy faceplate/grill, and there's a well-designed tube cage out back for TT owners with small children or pets. Very domesticated. The tube-phobic but curious among you can relax: VTL pre-installs and biases the tubes, and they strongly recommend your dealer inspect the amps and install them in your home. Luke Manley is obsessed with reliability so he's put together a major quality control effort at VTL: A Teflon insulated wire loom keeps high voltages off the printed circuit board; every solder joint is inspected; the mechanical assembly is QC-ed; all voltages are checked; and the amps are burned in for a minimum of 24 hours--sometimes as long as a week! Then the amps are checked again. With a tube complement of four Russian Svetlana EL84s and a pair of Philips 12AT7WTs, retubing these little guys won't break the bank (VTL predicts a 3,000-hour life span). Like I said, they're very domesticated.

If you're looking to rock and roll with the Tiny Triodes or any low powered tube amp, you had better have very efficient (90dB and higher sensitivity, with moderate to high impedance curves) loudspeakers. Then again, not all watts are created equal: The TTs' 25 watts feel stronger than the 20 watts of a Cary 300SEI I compared them to. Feisty little buggers! Using the TTs with my 89 dB efficient Anthony Gallo Acoustics Nucleus References, I played very dynamic piano recordings such as like Chucho Valdes' Bele Bele en La Habana at satisfyingly high levels in triode mode--without audible distress. Yes, the large scale, heavily percussive runs were blunted somewhat, but the Tiny Triodes consistently belied their Lilliputian dimensions.

I'm a major Loudon Wainwright III fan, so I got a big kick out of his recent release, The BBC Sessions. While the Tiny Triodes always stress music over hi-fi sound, they are nonetheless discriminating enough to reveal differences between various recording acoustics and even microphones as heard on tracks culled from more than two decades of his BBC appearances. The BBC Sessions whetted my appetite for more Loudo, so I pulled out his finest live recording (performance AND sound), Career Moves, and heard even greater resolution and more vivid sound than on the BBC disc. It's remarkable: I'm comparing recordings of just one voice and one guitar, yet the range of fidelity is so wide--and the best tracks give a surprisingly reasonable facsimile of a man singing and playing guitar. The VTL amps give me more than just Wainwright's sound--they give me something resembling his presence, his spirit, his ability to communicate a complex range of feelings through his music.

I used the VTLs in tandem with my Cary SLP-98 tube preamp for most of my evaluations, but I did try partnering the Tiny Triodes with the solid-state Linn Classik preamp/CD player. Sure enough, there were gains in detail, high frequency extension, and a dynamically contrast-ier presentation overall. Unfortunately, the losses in dimensionality and harmonic development didn't work for me, so I stayed with the Cary for the most part.

The Tiny Triodes are hardly universal amplifiers: They don't jive with the Dynaudio Contour 1.8 Mk.II speakers that sang so sweetly with the Cary 300SEI (the bottom end thinned out too much with the VTLs), but the TTs are a happening combo with the moderately efficient (87dB) NHT Super Twos. I wailed along with PJ Harvey's sonic head-on collision of a recording, 4-Track Demos, and then reveled in the raw power of Iggy Pop's underrated Naughty Little Doggie over the NHT/TTs. I exercised the NHTs' woofers with one of the best solo acoustic bass recordings around, William Parker's Lifting the Sanctions (No More Records). Parker's a wild man and his range of deep, thundering, throbbing, and manic bowing sounds are never less than astonishing. Within their power limitations, the Tiny Triodes' bass control, dynamics, and weight are satisfying, and the resonant "woodiness" of Parker's instrument is well portrayed.

The Tiny Triodes benefit from a couple of minor tweaks: Michael Green Audio Points for a little extra isolation, and an application of straight isopropyl alcohol to buff up the Tiny Triodes' tube pins--altogether upping the overall level of transparency a smidgen.

The VTL Tiny Triodes' performance exceeded my expectations on every count, and the real-world price clinches the deal. If you're interested in the littliest VTL, don't dawdle too long, 'cause when those 500 sets are gone, you might have to wait a long time to get something this wonderful for such a tiny investment.

Quality: ****

Value: ü ü ü

This review is reprinted courtesy of the Listener Magazine.  VTL would like to thank the magazine for this enthusiastic review and the opportunity to reprint it on our Web site.