Listening
My favorite part of any evaluation is the listening portion. For this session, I connected the front channels of the Roadster 66 to a pair of high-quality component speakers and the subwoofer channel was connected to an RSd 12" woofer in a sealed enclosure. To fully tax the power supply, but not skew my listening with additional speakers, I connected the rear fullrange channels to my load bank and set it for 2 ohms.
Adjusting the front channels to 40Hz highpass, and the subwoofer channel to about 80Hz lowpass, I sat down to play some tunes. The first thing I noticed was unlike so many others these days, this amp turns on and off absolutely silently, like a well-designed amp should.
Within a few minutes, I knew I was going to like this amp. The fullrange channels provided a noise-free, very articulate signal to my component speakers and the amp produced an exceptional stereo image. The subwoofer channel easily drove the single 12" woofer to its limits with no unwanted noise or annoying muddiness I sometimes hear with Class D amps. I could turn the amp up to very loud levels, and even with the rear channels loaded at 2 ohms, the big amp showed no signs of stress or lack of power.
I sat and listened for the better part of three hours, playing everything from Bach to ZZ Top. To sum it up, like the other Phoenix Gold RSd amplifiers I've heard, from a sonic perspective the Roadster 66 is a very good-sounding amplifier. It has very low noise for a multichannel design and all the power one might need for a serious system conveniently wrapped up in a single chassis.
Performance
After my listening evaluation was complete, I moved the amp to the test bench to see just what kind of numbers I'd get from it. The first set of measurements were all about power and I'm happy to report that the big Roadster 66 met every one of the power specifications published in the manual, with all channels being driven to full power simultaneously. Distortion at rated 4-ohm power on the fullrange channels was very low at 0.07 percent and also reasonable on the Class D channel at 0.2 percent. At full power into 2-ohms, I measured the amplifier's efficiency at just over 67 percent, which is good for this type of design.
Compatibility with various source units and OEM radios shouldn't be a problem either, with input sensitivity control ranging from 200mV to over 9 volts. This amount of "gain range" allows compatibility with virtually any source.
Frequency response measured flat within 3dB from below 10Hz to 66kHz. The gain pots tracked very accurately as well, which may have contributed to the amp's imaging capabilities I mentioned earlier. It's pretty common to find discrepancies of as much as 2dB between the left and right channels, but this sample tracked almost perfectly, with only an inaudible 0.1dB of difference.