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A/V receiver nails cost, performance tradeoff

Posted: 30 Aug 2007 ?? ?Print Version ?Bookmark and Share

Keywords:home A/V receivers? HD video? 1? 080p HDMI?

When it comes to balancing cost and performance, few areas are as demanding or competitive as home A/V receivers. Consumers want everything (though they don't want to pay for it): 7.1 surround sound and high-definition (HD) video, 150W of full audio-range power per channel with 0.001 total harmonic distortion and all the latest codecs and I/O options, from HDMI to banana plugs. Add reliability and aesthetics, and the requirements can quickly become untenable.

Enter the designers of Pioneer's VSX-1016TXV receiver. The 1016 appealed to me as teardown fodder for two reasons. First, it's an interesting system with design issues related to audio that range from the design of the power supply right through to noise mitigation in the digital portion.

Second, it is a reasonably priced receiver, with an MSRP of $499 and aspirations to equal the quality and performance of midrange systems priced at $1,000 or more. This demanded that the designers find ways to extract component and manufacturing costs without compromising performance. According to the reviews and my own experience with the receiver, the team managed the trade-off admirably.

Multi-featured device
The main features of the receiver are 7.1 channels, 1,080p HDMI, 110W/channel, THX Select 2, Dolby Digital EX, DTS-ES and DTS 96/24, WMA PRO multichannel and XM HD radio readiness, with Neural Surround. Inputs include eight video, three audio, five A/V, two HDMI, six optical, three coax, five S-Video and three component video. There are two video outputs, one XM-ready output, one HDMI 1,080p-compatible output, one optical digital output, four outputs for S-Video and one for component video.

According to Shirou Suzuki, Pioneer's design project leader on the VSX-1016TXV, the team sought to reduce cost without compromising performance. He said the designers had to "provide customers exactly the same sound quality for all channels in all respects, and recreate the studio engineer's original intent" in the consumer's home environment.

The first task was to reduce the number of unnecessary components to get the drastic cost reductions the team sought. One way to do that was to optimize and improve every circuit part with every block. "We focused on every capacitor and resistor, [assessing] whether the parts were really necessary," Suzuki said. The team negotiated heavily with device suppliers to push costs down further.

That led to a design with a paucity of passive components. The power supply essentially comprises two D5SBA 20 Shindengen diode bridge rectifiers, a hefty (4.53kg or 10lbs) ATS7407 power transformer and two Nichicon capacitors for output-amplifier power stability.

The signal input and output circuits were spread across three PCBS in a stacked configuration and were driven mainly by HC4051A and LVX4053 analog muxes and demuxes from ON Semiconductor. In addition, there is one LA7109 75 DVD video driver from Sanyo and a PDC131A character generator from Pioneer. The latter is likely for video overlay purposes on the video input. A Pioneer-marked ASIC controls the I/O network.

Kawasaki's MotoGP

The Pioneer VSX-1016TXV achieves high-level functionality, performance and aesthetics with low costthe classic engineering tradeoff realized.
(Click to view image.)

All signals eventually lead to the heart of the system: the DSP block. According to Suzuki, the first estimates before starting the design indicated that some combinations of functions would push the processing requirements to more than180MIPS. That would exceed the limits of the Freescale DSPC56371AF180 24-bit DSP the company had been using. Nonetheless, "our DSP software engineers were determined to achieve [the design] with only one DSP LSI" to keep costs down, said Suzuki. An intense cooperative effort with Freescale's own DSP development team yielded success.

The single DSP now runs Pioneer's Digital Core Engine, providing all of the receiver's multichannel sound processing. That processing covers eight advanced concert and cinema surround modes, including the various Dolby modes, Pioneer's own Multi-Channel Acoustic Calibration system and other original sound enhancement processing, along with THX and WMA9 Pro.

The DSP is supported on the same pc board by the popular AKM AK4628A 96-kHz/192-kHz, 24-bit, two-channel A/D converter and eight-channel D/A converter (with on-chip switched capacitor filter and 106-dB dynamic range), the AKM AK4114VQ digital audio interface and an XM satellite radio tuner. The team went with the AKM converters "to achieve the high-quality S/N [signal-to-noise], frequency response and THD [total harmonic distortion] required by THX," said Suzuki.

The video decoder and overlay board comprises the two HDMI inputs and single HDMI output. These are driven by an Analog Devices ADV7184 multiformat SDTV video decoder with fast switch overlay support as well as an Analog Devices ADV7172 digital PAL/NTSC video decoder.

The main processor board comprises a Freescale 24bit DSP (right) supported by AKM converters and an XM-HD tuner (bottom, middle).

The addition of HDMI interfaces proved problematic. The addition is new for the VSX line and the radiated interference caught the design team off guard. "Some engineers in charge of HDMI, the digital audio block and the main motherboard were suffering from the radiation problem," said Suzuki. While he would not be specific in terms of how the team resolved the issue, he said that the team members are expert at resolving such radiation problems and that they applied their own "theoretical method and experience."

The amplifier section, meanwhile, relied on Pioneer's own Advanced Direct Energy (ADE) MOSFET design to produce highly efficient, high-end sound for each channel. According to Suzuki, the technique allows loudness with high quality, a sometimes difficult combination. The amplifier section comprises 14 SK SAP 17 MOSFETs spread across two finned heat sinks.

It's interesting to note that after I presented a teardown of the VSX-1016TXV at the Freescale Technology Forum in June, two designers from a high-end A/V company (which shall remain nameless) approached the podium and expressed disbelief that Pioneer had combined the parts and features of the amplifier at such low cost. One went so far as to say that his company used many of the same parts and components, but their price point was much higher.

The comment served as testament to the tenacity of Pioneer's VSX-1016TXV design team.

- Patrick Mannion
TechOnline




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