New DAC Chips from AKM Semiconductor Push Audio Performance Envelope

High-end digital audio's rapid advancements are pushing integrated circuit designers to exceed their previous limits. San Diego-based AKM Semiconductor has joined the chip elite with two new digital-to-analog devices that further push the performance envelope. The AK4394 is a 24-bit/192kHz stereo DAC based on Asahi Kasei Microsystems' advanced multi-bit delta-sigma technology. Its sibling, the AK4356, is a 24-bit/192kHz, six-channel DAC based on the same technology, but boasting a useful and fascinating array of features.

AKM claims the AK4394 is "the industry's best-performing standalone solution for the 192kHz audio sample-rate standard"—a claim backed up by the device's specified dynamic range of 120dB—"while maintaining the superior distortion characteristics of conventional single-bit designs." The AK4394 is pin-compatible with its predecessor, the 96kHz-sampling-rate AK4393, and is expected by its manufacturer to find its way into many DVD players, digital mixers, digital audio workstations, and other digital audio applications.

The 28-pin chip supports 32kHz, 44.1kHz, 48kHz, and 96kHz sampling rates with digital de-emphasis. Its onboard analog output stage uses a switched-capacitor filter capacitor circuit—said to provide "exceptional tolerance to clock jitter"—and operates in fully differential mode. Massive integration reduces the number of external components. In fact, AKM describes the AK4394 as "a complete high-performance single-chip stereo digital-audio playback system."

AKM's six-channel DAC, the AK4356, incorporates three multi-bit stereo DACs for high-quality digital audio playback of 96kHz-sampled audio, with six-channel analog outputs. Two of these channels can be used in 192kHz sampling mode—useful for playback of DVD-Audio discs, whose two front channels can run at 192kHz while the other four operate at the lower rate of 96kHz. Demonstrations and lab tests indicate that 192kHz offers the higher degree of transparency of the two, although 96kHz-sampled audio can also sound excellent. High-end players are expected to take full advantage of everything this advanced technology can offer.

The 44-pin AK4356's 112dB dynamic range isn't as high as the 4394's, but is still very good. The device's six analog output stages adhere to the same architecture as the 4394's, with switched-capacitor filters and fully differential output. Independent digital volume control for each channel, a soft-mute function, and channel-independent digital de-emphasis for 32kHz, 44.1kHz, and 48kHz sampling rates make the AK4356 the "one-chip solution for multichannel audio." Manufacturers can obtain the AK4356 for $4.15 each in lots of 10,000.

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