Every once in a while a product comes along that demands re-examining one’s audio assumptions. These assumptions, accumulated through personal experience, consensus, and “What so-and-so said,” all too easily solidify into unexamined fact, and often fossilize into rigid dogma. The Sonic Impact Model 5066 T-Amp challenges these assumptions.

To be truly High End and musically convincing, a component must:

1) Produce at least 300 watts of power per channel.
2) Be of Single-Ended Tube triode design based on the 300B tube.
3) Use Class A solid-state architecture.
4) Have enormous power supplies.
5) Weigh at least 75 lbs. and be built to withstand nuclear attack.
6) Cost at least $5000.
7) Avoid anything ‘Digital.’

We’ve all heard such ‘facts’ and perhaps even flirted with them ourselves. The Sonic Impact T-Amp defies them all. What does one make of a $39, 6 watt per channel, digital portable amplifier marketed to the MP3, portable CD, “on-the-go” set? From the conventional viewpoint of Audiophilia and The High End, it’s not even worth considering. But then…

Don’t audiophiles routinely spend thousands of dollars on power cables, AC conditioners, and re-wiring their house AC with hospital-grade plugs? Wouldn’t it be nice to be free of all the vagaries of AC? The Sonic Impact T-Amp runs on batteries. Wouldn’t it be also nice to get rid of all the heavy seat sinks needed to keep mega-amps from melting? The Tri-path chip used in the Sonic Impact doesn’t need any heat-sinking, as it runs 81 to 88% efficient based on speaker load. And while we’re at it, let’s get rid of huge power supplies and output transformers too. Enter again the efficiency of the Class -T architecture. Those cheapskates who cringe at having to replace batteries can invest in an AC power converter for $25 or so.

Bad news, though, for those who automatically equate high performance with high price: a little judicious shopping reveals prices as low as $21, though $29 seems the average. (I paid $29.87 at Parts Express, plus $23.49 for an AC adaptor.) That is, if you can find anyone who has them in stock. As the word has gotten out about the T-Amp, it’s been selling as fast as an Angelina Jolie instructional video on the proper way to eat a popsicle. The good news is that I personally intend to sell a Signature version of the T-Amp for $5,999. Basically, I intend to stack them in a corner and play Bo Diddley at ‘em all day long. Then, I’ll sign each box. As the Chicago hitman, arrested after accepting a contract to murder his parents, offered: “Hey, I’m just trying to make a buck!”

Low power output is less shocking a concept to the mainstream these days as the low-powered, Single-Ended Triode enthusiasts become less underground. Indeed the first to discover the virtues of the Sonic Impact amp have been aficionados of low-power tube amps. As if to dispel the digital dragon, one of the leaders of single-ended tube design – Bel Canto - now makes digital amps based on Tri-Path chips.

Since high mass exacerbates, indeed invites, environmental vibrational interference, the lightweight T-Amp won’t need isolation products. I’m investigating a “Signature” series of paperweights to keep the amp from becoming airborne in gusty March winds. (Expect to pay through the nose.) Metal casework is a contributing factor in attracting EMI/RFI; the plastic case of the T-Amp looks likely to be immune. Hey! Wait a minute! This amp is really avant-garde! Maybe I misread the price and it’s really $3995?

I consciously use a review methodology which I call “Applied Phenomenology,” which stripped to its basics could be summarized as “Cast aside your biases and assumptions, keep an open mind, and listen, really listen, to the component on hand.” Consequently I have no particular axe to grind concerning tubes or solid state and even the “D” word holds no terrors. That CD was a-musical and un-listenable for the first dozen or so years of its existence doesn’t mean that all digital products are going to be musically inept, though I admit that the 1984 NewThink and GroupThink that surrounded the initial CD hype makes me adopt a “Show Me” caution when new digital technologies announce that the Emperor has New Clothes. Though I’ve been aware of emerging digital amplification technology since the mid-70’s when Infinity announced development of a digital switching amp, I have not followed recent digital amplification progress with anticipation, aware that any technology always involves trade-offs and that New doesn’t automatically equate with Better. The proof is always in the listening.

Listening to the Sonic Impact T-Amp requires some adaptation: the single input is a stereo mini-plug and speaker connection is through spring-loaded clips designed for bare wire and speaker pins. One prong of the old small tube barrier-strip spade lug will also fit and the adaptor box I use to connect contemporary cables to my old EICO tube amp eliminated this potential inconvenience. Nor was input a problem as a gold-plated mini-plug to stereo RCA-jack adaptor costs all of 5 bucks. Those stymied by the single input can use an outboard line-level switchbox to multiply inputs, or treat the T-Amp as a power amp and connect a conventional preamp.

The T-Amp takes a good 50 hours of initial play to come into its own. From turn-on, about 5 minutes will bring it into song. The difference between battery operation and AC was inaudible with the medium-sensitivity speakers I used and I gave up after 18 hours of trying to see how long a set of 8 AA cells would last. I tried Stillpoints’ ERS cloth to see if the T-Amp was producing or susceptible to RFI/EMI. Since I place components horizontally rather than vertically and my stucco house is very good in being free from this interference, I could hear no difference.

The major obstacle for good inexpensive gear is that it’s likely to be used with crap inexpensive gear and its true merits never revealed. Using the T-Amp with my computer and then using it in bypassing my TV’s built-in amp and speakers only hinted at its clarity and resolution. Assaying interconnects yielded excellent results from a variety of affordable items, including entry-level items from Audioquest and Kimber. The improvement as I moved to my usual reference Origin Live was startling, so it’s worth running the best interconnect one has available. Speaker cable choice was a bit perplexing, as I really couldn’t assume that cables that I’d found complementary to tubes or solid-state in the past would work with a digital amp. I got surprisingly good results even with ordinary 18-gauge zipcord, you know, that stuff we all used to use to connect speakers before cables became a component in themselves? Cutting edge.

OK, there is an elephant in the room: how do you maximize 6 watts per channel? The obvious solution is to use high-efficiency speakers – say, 93 dB sensitivity and up. Even better if they’re a 4-ohm impedance: now you’re getting 11 watts per channel. Since I didn’t have any high-sensitivity speakers available, my review is somewhat compromised and I’ll do a follow-up when I get a chance to listen to the T-Amp with truly high sensitivity speakers.

The other approach is to use the amp with more common sensitivity speakers and keep an ear on the volume levels. Using a smaller room also helps enormously, seriously cutting down the power needed for any given volume level. The idea is to keep speaker demand and volume levels within the envelope of the T-Amp’s power output. Some care must taken however; as any speaker repair shop will tell you, most speaker damage is done by smaller amps being grossly over-driven. I used the Celestion 3 Mk II – 88dB sensitivity, 8 ohms; the Celestion F15 – 89 dB, 8 0hms; the Spendor 2040 – 87 dB, 8 Ohms; and the Infinity Qb – 87 db, 4 Ohms. The last two are ‘full-range’ by my definition, and produce linear in-room response into the 30 Hz range. Since I rarely exceed 85 dB SPL while listening, I had no problem hitting the mid and high 80’s in either of the two 12 ft. by 18 ft. rooms I used for most of my auditioning.

The Sonic Impact does not sound like the typical tube amplifier, nor does it sound like solid state. It doesn’t have the levels of 2nd harmonic distortion that many tube designs produce, nor does it present the typical ‘loose bass’ that bedevils many tube designs with mediocre output transformers. It doesn’t sound like a bi-polar solid-state amp, nor is it reminiscent of Class A or MOSFET designs. Sonic Impact doesn’t list any figures for dynamic power output, output impedance, frequency response bandwidth, or damping factor, making it easier to avoid making assumptions about what the amp will or won’t do.

The most immediate and lasting impression of the Sonic Impact 5066 is its exceptional clarity: it rivals many cost-no-object designs in this regard. Vocal reproduction, lyric intelligibility, articulation of harmony singing, and lead/background vocal distinctions are excellent. Ditto for retrieving the ambience around vocals. The high-frequency response allows clear differentiation of the differences in the ultimate quality of tweeters: the classic EMIT of my old Infinity Qb’s still handily outperforming the modern aluminum and titanium domes of the Celestions and the silk-dome of the Spendors. Plucked strings are very vivid and separation of complicated multi-percussion recordings was very good. Bass response is tight, fast and controlled at least into the high 30 Hz range of which I could make a reliable judgment. No boom or loose slurring, though the bass did seem to be down in level compared to the mid-range and high frequencies. Perceived tonal balance is a slow gentle rise from the mid-bass on up: the amp doesn’t sound rolled-off or dull, or mellow. Nor does it sound etched or excessively zippy.

The T-Amp’s perceived clarity allows sound-staging and stereophony to reach hallucinatory stereoscopy: near-field listening with the Celestion F15’s revealed a stereo illusion that would satisfy even the most visually-oriented audiophile. The amp is certainly quiet, descent into silence at times so abrupt as to be startling.

The T-Amp passes all the usual audiophile criteria to be superficially impressive. It is only when looks at the core musical values that flaws show up. Timbre of instruments is not completely accurate and is occasionally confusing, particularly on orchestral music where oboe/English horn, the subtleties of the French horn, and flute/piccolo differentiation can be foggy. Rhythm and pulse are only good; phrasing, parsing, and expression the same. Occasionally the amplifier loses control of complicated rhythms or complex orchestration, leading to the perception that the band or orchestra has lost its groove and the inner meaning of some music is either lost or compromised in its impact. Since these criticisms apply also to very expensive high-end gear at one hundred or more times the 5066’s price (some of which couldn’t dance if they had James Brown welded to their ass,) it may seem unnecessarily cruel to apply it to an amplifier that costs only $39.95. The demands of music, however, are the demands of music.

High levels of clarity do not automatically equal high resolution and high detail retrieval. Just as a winter landscape abstracts and clarifies the lines and forms of trees and landscapes, you can produce the sensation of clarity by leaving information out. Listening to the Sonic Impact with LP playback revealed that some of the flaws mentioned above echoed the limitations of the CD medium itself. With analogue sources, the T-Amp’s timing and rhythm improved to G+ from a straight G. Timbre quality also improved significantly, though still short of being completely accurate or believable. Also revealed was the amp’s lack of ability to track decay of notes properly. Rather than allow the smooth, continuous decay into silence, the amp’s portrayal of decay moved in discrete truncated steps in an unnatural manner. This lack of ability is likely the cause of the slight falsification of timbre, as close listening also reveals that initial transients are also modified, and the natural progression and bloom in time of each note is not completely mastered.

Using the Sonic Impact to drive small speakers supplemented by a powered subwoofer is the other obvious solution to its low power output. Freed from having to provide power for the bass frequencies, the 6/11 available watts have more grace and urge. This application also eliminated the 5066’s tendency to lose instruments in complex mixes and orchestrations, musical lines in the bass being much easier to follow through denser mixes.

Most modern loudspeakers are designed assuming conventional solid state amplification, not only in power output, but also in damping factor, output impedance and bandwidth, thus shortchanging tube amplifier users in general and low power tube amp users in particular. Home Theater has created a demand for more sensitive loudspeakers with easy-to-drive impedances in general, but the kind of sensitivity low-powered amps require still yields a very small field in loudspeaker choice. Many speakers designed for low-power tube amps use single drivers and ultimately butt up against hard physical laws concerning bass and high frequency response. Horn-loading and other techniques to magnify sensitivity and/or bandwidth have enjoyed a resurgence of attempts to eliminate their long-known distortions, and the increased demand for higher sensitivity is a boon in my opinion. I would personally like to see average sensitivity be 93 Db rather than the 87 or so that is the current norm. All this is to say that I don’t feel I can make a firm judgment of the 5066’s ultimate dynamic and bass abilities until I can mate it with more compatible sensitivity speakers.

Let’s face it: for most of us, the Sonic Impact is FREE. As such, every audiophile should own one just to see what can be done with technology that will likely be everywhere from phones to TV’s: in fact any amplification need that would benefit from lost-cost and high efficiency. Though far from perfect in reproducing music in high-performance systems, listening to the T-Amp can be a revelatory experience and force re-thinking the solidity of common audiophile assumptions. Those brought up on CD (or worse yet, MP3) might not find the T-Amp’s flaws fatal: for me, however, the amp’s inadequacy in portraying the attack transient, bloom and decay of each note corrupts the music at its heart, and thus will relegate the amp to the interesting experiment category rather than qualify it as a totally successful musical device.
 

Paul Szabady

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Specifications:
Portable, battery-powered, digital integrated amp.
Class-T ™ architecture incorporating Tri-mark TA 2024 digital amplifier chip and Digital Power Processing ™ technology.
Uses 8 size AA batteries, Optional AC converter.
One stereo mini-plug line input.
Power output: 10 watts/per channel – 8 Ohms, 15 watts per channel – 4 ohms @ 10% THD. 6 and 11 watts/channel (respectively) at 0.1% THD.
Dynamic Range: 102 dB.
88% efficiency @ 8 Ohms, 81% at 4 Ohms.
Size: Fits in the palm of your hand – 8” x 6” x 2”.
Weight: Fly-away without batteries, 1 lb. with batteries.
Price: $39.95.

Address:
Sonic Impact Technologies LLC
San Diego CA 92101
Website: http://www.si-5.com/