Sonic Impact Technologies T-AMP 2-Channel Amplifier

Introduction
Without a doubt the Sonic Impact T-Amp is the best amplifier you can buy for it's typical $30 street price. Of course, saying that is kind of damning with faint praise. Actually, this is the best amp you buy for less than $100, perhaps even $200. No kidding.

I first heard about the T-Amp back in Oct. 2005 when word of it spread through the geek/gadget blogosphere like wildfire. It seemed hard to believe at first -- a $30 battery powered amplifier that audiophiles are saying will best amplifiers costing hundreds or even thousands?

But when I learned that the T-Amp is powered by a little digital amplifier chip, I became more credulous. Digital amplifcation is just starting seep into mainstream electronics, mostly from big Japanese electronics manufacturers like Panasonic and JVC, and I think that's a good thing.

A Useful Tangent: What the Heck's a Digital Amp (and Why Does It Matter?)
(Those of you less interested in the geeky details can just skip ahead).
An in-depth overview of digital amplifiers is beyond the scope of this review, not to mention my abilities. But to understand what makes a digital amplifier unique, you have to understand that audio amplification is always a game of compromises.

The simplest, and best sounding amplifier designs are called class-A, and they sound so good because they are always on and amplifying, regardless of how much power is required by the audio signal. As you might guess, that's pretty inefficient, so class-A amps tend to produce a lot of heat for the amount of effective wattage they pump out.

So most amplifiers out there are switching amps of some type or variety. This means they switch off and on depending on the program matter. In this equation some degree of sound quality is traded off in exchange for more efficiency and less heat.

A digital amplifier is a type of switching amplifier that takes switching to a whole new level by switching at a rate of thousands of times a second. As it happens, this is how digital audio sampling works, and they're based on the same ideas. Properly designed, digital amplifiers are both very efficient and very good sounding.

Ready To Believe
The reason why I was ready to believe the T-Amp could be capable of good sound was because I already own a stereo with a digital amp in it from Sharp (reviewed here on Epinions), that blew me away with the clarity and quality of its sound.

So, for $30 plus shipping, I figured there was nothing to lose.

I was right.

The Arrival
Opening the box, I saw what I expected. A cheap plastic case the weighs almost nothing with just one dial, a little bigger than a quarter, on the front. On the back is a 1/8" stereo mini jack for your audio source, two sets of basic speaker terminal clips, and a DC input jack.

The T-Amp is designed to run on 8 AA batteries in order to provide its needed 12 volts. The battery cover is on the bottom, and when opened I found that about 2/3 of the inside of the case is taken up by the batteries. With batteries installed it's about three times heavier.

As luck would have it, I had 8 charged up NiMH AA batteries ready to go and I popped them in.

First Play
For my first play I dug out a Sony Discman and plugged it in using the supplied 1/8" male to 1/8" male cable. I also dug out two inexpensive B.I.C. RtR 432 bookshelf speakers I had and plugged them in with basic 14 gauge speaker cable that barely fit in the T-Amp's speaker jacks.

I turned the dial on and the front panel LED glowed red. But no other auditory signs that it was on. No click or pop, and no telltale hiss, even when I jacked the volume up all the way.

I started up a CD of John Coltrane's A Love Supreme with the volume knob set at 9 o'clock and Trane's signature tone came through with surprising clarity. Turning up the volume slowly brought up the volume with a little bit more depth, until at about the 3/4 mark, or 3 o'clock when distortion started to kick in.

The T-Amp is rated for 15 watts per channel, but most best real-world estimates put it at about 7 watts. That might sound paltry next to the chromed-up flashing bookshelf systems at Best Buy that declare hundreds of watts with red stickers. But in most listening, amplifiers are really only putting out a few watts unless you really push them. 7 watts can actually put out room-filling sound.

Second Play
Impressed with the results of the T-Amp with a Discman and inexpensive speakers, I decided to test it on my main speakers, a pair of Polk RT600i towers. The Polks aren't super efficient, so I wasn't sure what they'd make of just 7 watts, but I also figured they reveal more of the detail in the T-Amps sound, if it was actually there to hear.

I used my main CD player instead of the Discman and fired up A Love Supreme again. If I hadn't been the guy doing the wiring, I'd have thought that I was listening to my usual main system. I called my wife in to listen and she agreed.

Again, I could get the volume up to about 75% without distortion, and that was pretty loud. Not so loud that you couldn't yell over it, but loud enough to overwhelm normal conversation.

And the sound, it was clear, precise, with really nice transients. Bass was solid and present, Trane's sax tone alive and full. If I had to label the sound, I'd say it's a bit dry, lacking in coloration, almost to a fault.

Third Play
For my third listening test (within an hour of opening it up) I plugged in my turntable, a Pro-Ject 1.5, via a Pro-Ject Phono Box preamplifier. I put a reissue of Ornette Coleman's The Shape of Jazz to Come (perhaps my favorite jazz record), and let rip with "Lonely Woman."

Coleman's plaintive tone came wailing through, and frankly sounded more clear and alive than it does on my normal system. I attribute this to the fact the T-Amp was running on batteries and I tend to have a small problem with a 60Hz hum -- a common problem with turntables. But with the T-Amp no AC power means no AC power hum. I was taken aback.

Living with the T-Amp
I've owned the T-Amp for about three months now. After my initial week of listening to it, it got put away for a while. I just took it out again a couple of weeks ago and now I have now hooked it up in my home office using the Sony Discman and B.I.C. speakers. I use it when I don't want to listen to music through my PC, either because I'm doing something processor intensive, or because I want to listen to CDs.

Frankly, the T-Amp with the B.I.C. speakers and the Discman sounds better playing CDs than my PC does playing CDs through my Sound Blaster Extigy, harman/kardon receiver and JBL Control 1 speakers. The PC system has subwoofer, so it has more bass, but the T-Amp system has better midrange clarity, with cymbals that sheen just right, without sounding ragged or edgy.

As I write this review I'm enjoying Freddie Hubbard's Red Clay, and Ron Carter's bass on the live track has punch and presence without any artificial tubbiness. Billy Cobham's subtle snare rolls are fully audible and distinct. I am enjoying this CD and have to pause typing to pay more attention.

The batteries ran out tonight for the first time since I bought the Amp. I figure I got at least 20 hours of play out of them. However, it was disconcerting when they died, because the sound stuttered and stopped, even though the LED stayed on. Fresh batteries installed after a moment of panic showed that the amp still worked. My guess is that its voltage needs are pretty strict, and any dip below 12 volts means playtime is over.

Conclusion
Do not buy the T-Amp if you want sound that will throb or rock the house. Do not buy the T-Amp expecting to get a fine-crafted piece of equipment.

Buy the T-Amp if you want a little amplifier you can take just about anywhere that will deliver sound that's better than just about any portable stereo, boombox or bookshelf system out there for under a thousand dollars.

You can build a nice little bedroom or office system with the T-Amp as its base. It would also make a great suitcase system for taking outdoors or on a trip. It's the one audiophile amplifier you'd never worry about dropping or losing, because it costs about the same as a tank of gas.

The irony of the T-Amp is that you'll probably have to spend several times its price in order to get new speakers that are in its league. But I think you can pair it with a decent set of Polk bookshelf speakers and do OK. For a real value, check the classifieds or garage sales for some used speakers by a reputable brand.

Sometimes the hype is true, and for the T-Amp it is. If you like good high fidelity sound, spend the thirty bucks, you won't regret it.