Sonic Impact Portable T-Amp

I had a set of Infiniti speakers collecting dust in a closet (2 satellite speakers and 1 unpowered subwoofer).  I had a cheap set of powered speakers connected to my PC, but ever since I got an ethernet router they have been picking up an excessive amount of noise and humming whenever they are on.  I decided to get rid of the cheap speakers and buy a receiver to drive the nice Infinity speakers.  I looked for a long time for the cheapest receiver I could find, and the best deal I came across was for a simple 100 W per channel receiver for $79.  I really didn't need anything that powerful for computer speakers in a single home office room.  The large size of a standard receiver also turned me off since I don't have a lot of extra desk space.  The main purpose is to listen to music and computer sound effects while sitting next to the computer.

I finally came across a better solution from Sonic Impact.  They sell portable t-amp that can provide up to 15 W per channel for two channels for driving standard 4 Ohm or 8 Ohm speakers.  I was a little unsure at first if 15 W per channel would be sufficient for my speakers, but at about $26 and a small  8" x 6" x 2" size, I decided to give it a try.

This little device works great for this purpose and I have used it for a couple of years now.  I went to get another one for a different room (a case where I had a decent set of speakers and wanted to drive them from an IPOD source).  It turns out that Sonic Impact does not make the stand alone mini amplifier anymore.  They still make a plug in card for a PC with the same or similar amplifier circuitry on it, but in this case I really need the external stand alone amplifier.  I have not been able to find anything else similar in size, performance, and price either.  If anyone knows of anything like this I would appreciate it.

I believe the T-amp uses an amplifier similar to the class D type amplifier.  They call it class T, but I think it uses a similar principle of PWM driven outputs.  These amplifiers can be very efficient and small.  I worked on a project last year in which a class D audio amplifier was used and was impressed with audio quality that was attainable with this type of amplifier.  It can be a challenge to get such a configuration to pass electromagnetic emissions test because of the large amounts of power and switching frequencies.  The switching slew rates are very fast and this leads to a lot of broadband noise at very high frequencies 100 MHz - 1 GHz.