What about the tubes? Many people claim to prefer the "warm sound" of a tube. But generally speaking, the tube amps that they refer to used the tubes as output devices, and while tubes do exhibit even order distortion, which does not sound as harsh as the odd order distortion we get from transistors, the "warmth" to an amp using vacuum tubes as the output devices usually came from nothing more mystical than a rolled-off high frequency response.
The tubes in this amp appear to be used for a small amount of gain in the preamp signal path, and I don't believe they have a huge effect on the overall sound of the amp. But, then again I had no way to do a direct A/B comparison of the circuit with and without them. They do, however, look cool and make a statement that this is no ordinary amplifier. Remember, these tubes are not used as output devices like they are on a conventional home audio tube amplifier. The TA2 uses proven bi-polar transistors for the outputs, which for many reasons are an infinitely better choice than tubes as outputs for a car amp.
There is also some information in the manual about allowing the amp to warm up for at least 30 minutes to get the best performance. The turn-on delay times varied throughout testing, from just under two seconds when warm, to about seven seconds when the amp had been off for several hours. That's a little odd, but I sort of like quirky gear - it adds personality.
Despite the independent power supply circuitry and the non-bridgeable design, the stereo separation figure was 52.5dB, which is about average for a well-engineered amp.
Although the TA2 uses some very nice detented potentiometers for the independent gain controls, I did notice a small issue when setting them. You'd expect the advantage to having detents in the gain pots would be to allow you to simply count the clicks and set both of them the same. But don't put away your trusty voltmeter just yet, because I found the counting click method to be off by as much as 0.5 volts depending on where you were in the pots rotation. In roughly the center area of adjustment, the channels need to be set about one click different from each other (left at 13, right at 14) to minimize the difference in output voltage between channels. Still, the independent pots were nice, and I'll concede that even just matching the detents would get you closer than some ganged pots do. The crossover adjustment potentiometer was spot on however, with the range from 20Hz and 200Hz measured exactly as indicated.
Inter-channel phase differences measured very low, at only 0.9 degrees at 20kHz, partly due to the lack of bridging capability, and also the high-speed, high-quality parts in the preamp section. Low inter-channel phase differences contribute to good stereo imaging.
ManualThe Ultimate TA2 comes with a decent six-page manual, outlining the specifications, controls, connections and troubleshooting topics you'd expect. This amp is basic enough that any installer worth his Makita would not require any help, but in the manual there are some good tips and advice that make it a good thing to read, especially if you've never installed a DLS amp. But unfortunately like most manuals, it will probably never be read.