Rotel RSX-1560 A/V Receiver Page 2
The RSX-1560 includes a couple of welcome tweaks from previous generations: The front-panel power button now switches between on and standby (versus on and hard power-off in older Rotel receivers). And the receiver now remembers the status of the multichannel analog input. If you switch it on, it stays on through future power off/on cycles. While the remote is smaller, the control layout is similar to its 2001-era predecessors. It works fine on axis, but it lacks the RSX-1065’s supernatural ability to accept infrared codes regardless of where you aim the remote.
As an audiophile product, this receiver omits some features that would otherwise be standard at this price. They include auto setup, room correction, satellite radio, and iPod docking. SACD enthusiasts will be irked to discover that the RSX-1560 doesn’t include DSD decoding, so the receiver won’t accept these signals via HDMI. You’ll need to keep using the cumbersome multichannel analog interface.
But Rotel has its own idea of what’s important. One priority is a PC application that smooths the rigors of setup by giving the dealer, installer, or advanced user a spreadsheet that lays out all the options. You can keep a settings file with all of your goodies in case something happens and the receiver needs a full reset. To download this, go to www.bwgroup-support.com/rotelsetup.html.
Tall Cool One
At the heart of the RSX-1560 is ICEpower amp technology that’s licensed from a subsidiary of Bang & Olufsen and extensively modified by Rotel. If you think this receiver is expensive at $2,599, consider the fact that the same amp module (modified differently) sells for a lot more in other products.
At 34 pounds, the receiver is heavy, but not as heavy as the 54-pound pure Class AB model it replaces, the RSX-1067. Because a Class D amp converts less power to heat than a Class A or Class AB design with the same power rating, it eliminates the huge metal heat sinks altogether. It also functions with a smaller power transformer and capacitors. (I can’t disguise the fact that I’ll miss my RSX-1067 reference receiver’s huge front-mount heat fins. Still, given how much heat they threw off, and the fact that coal and nukes generated much of that wasted power, perhaps it was time to say goodbye. I am almost sobbing as I write this.)
Most receivers are Class AB, which means they keep each device in their output stages running part of the time. This delivers power to the speakers when the signal dictates and dissipates the remaining power in the form of heat. The Class A amps that some audiophile two-channel systems use are even less efficient. They run their output stages all the time, burning power even when there’s no input signal at all. In contrast, this Class D receiver achieves about 80 percent efficiency at full power, compared with the roughly 30 to 60 percent efficiency of the all-analog designs it replaces. Many Class D amps are even more efficient, at about 90 percent at full power, but Rotel’s audio-savvy design sacrifices a smidgen of that energy savings.
How does a Class D amp achieve that greater efficiency? Like any kind of amp, it starts with an analog input signal. It then creates a replica of that signal as a train of pulses, a process called pulse width modulation (PWM). The train of pulses is then amplified by a rapidly switching output stage, which is always either on or off. The switching frequency is 384 kilohertz, about 20 times as high as anything that the human ear can detect. Finally, the amp low-pass-filters the amplified pulse train to recover the analog waveform and eliminate the ultrasonic switching noise. What emerges is a gush of analog power fit for your speakers—of course, conventional speakers are always analog devices.
Perhaps counterintuitively, the conversion of the analog input signal to a pulse train is not considered a form of digital encoding. This is how Rotel puts it: “This process seems digital but is in fact analog in nature. The signal is not digitized, i.e., assigned a numerical value. The pulse train is an analog of the input audio signal.”
Sounds like a piece of cake. But although it’s elegant, the process is not simple. To prevent the on/off process from pumping the power supply, Rotel’s designers added an adaptive circuit. Since loudspeakers’ impedance varies with frequency, the output stage must provide a low output impedance and a high damping factor to contend with the real-world loads that speakers present. The final act of filtering must remove high-frequency noise, which is inherent in the switching process. Both the switching stage and the filter use feedback to control the PWM process’ side effects. This is not an off-the-shelf chip amp in a fancy metal box.
Associated gear included five Paradigm Reference Studio 20 v.4 speakers, running full range without a sub. The main signal sources were a Panasonic DMP-BD55 Blu-ray player, Rega Planar 25 turntable, Shure V97xE cartridge, and NAD PP-1 phono preamp. All movie selections were Blu-ray Discs with lossless Dolby TrueHD surround.
Quarantine plunged the Rotel into the deep end of the pool with a hyperaggressive soundtrack. The bombardment of sound reflects the confusion of potentially violent people who are confined to an apartment building by the health authorities—the kind of health authorities that use helicopters and machine guns. Muffled but loud copter and siren noises revolved crazily around the soundfield, slowly driving the occupants mad, and some of that rubbed off on me. Overall, the soundfield was murky and uniformly loud, not unduly fatiguing, but relentless. It occasionally offered moments of startling realism. At least once, I paused the disc to verify that the sirens weren’t outside my building. In this and future selections, I set the master volume at a minimum of 60 increments out of a total of 99, and often up to 65, so the receiver was operating at just under two-thirds of its maximum gain. The sensitivity of the Paradigms is about average, at 88 dB.
Made of Honor is a gentle comedy about a guy who becomes the maid of honor as the woman he loves—the always delightful Michelle Monaghan—is about to marry another guy. It’s predictable in a nice way, and it’s apparently mixed for TV speakers, as so many comedies are. Reproducing dialogue was a piece of cake for the receiver.