The first in a series of reviews of outboard DSP processors available in the market and of interest to loudspeaker engineers, this article explores an extremely versatile and powerful DSP audio processor and DAC, crossover, and control center for any audio system. The dspNexus comes with balanced inputs and outputs, USB, S/PDIF and Bluetooth aptX HD, and processing is handled by a latest-generation Analog Devices SHARC DSP, with Audio Weaver as the programming interface.
What differentiates this new outboard dspNexus processor from the rest of the outboard units I will be reviewing (Marani Pro Audio MIR480i and MIR260A, miniDSP Flex, and a rackmount unit built around Danville Signals’ Greywolf OEM DSP boards), is that dspNexus is not only a two in/eight out crossover DSP processor, but it also functions as a preamp. In terms of inputs, dspNexus can switch between balanced analog stereo Input, USB Audio Class 2, S/PDIF, and Bluetooth Audio (aptX-HD). Since digital sources come in all sorts of sample rates and levels, the dspNexus automatically up-samples to either 192k or 384k, performs jitter attenuation, and remembers the volume settings for each source independently.
Other features include room correction and bass management, digital RIAA for vinyl recordings, a headphone amplifier, and a 48V phantom microphone input for making loudspeaker and room measurements. All this makes it ideal for home audio users, which is probably why dspNexus was such a hit at the recent AXPONA two-channel audio show in Chicago, IL.
dspNexus is available to single users and it is also available in customizable OEM configurations for all three versions, which includes the subject of this explication, the two in/eight out dspNexus, but also the two in/two out and two in/four out units. Case cosmetic variations can be made available, plus the LCD screen (Photo 3) can be programmed with the manufacturer’s brand name and model nomenclature.
In terms of hardware (Photo 4) all units feature the most advanced Analog Devices’ Sharc chips as well as the AKM “velvet sound” ADC/DAC. For the AKM converter chips, the standard unit comes with the AKM 4493 with the option of incorporating the AKM 4499. Programming for dspNexus is performed via a proprietary copy of Audio Weaver, undoubtedly the most advanced DSP programming software in the industry.
All the outboard units in this series of explications were measured on an Audio Precision flagship AP555B analyzer courtesy of my friends at Audio Precision, with a special “Thank You” to AP engineer Charlene Chow, who performed the measurement sequences for this article. Photo 5 shows the basic setup for the series of tests. Test categories that were performed included total harmonic distortion plus noise (THD+N), signal-to-noise ratio (SNR), frequency response at 0dB, crosstalk, and intermodulation distortion (IMD). Starting with THD+N (Figure 1), at 1kHz the number was 91.864dB, and although not shown, the numbers were 91.334dB at 50Hz, and 93.450dB at 10kHz. Figure 2 depicts the SNR graph, which resulted in 101.663dB.
Frequency response for the dspNexus (Figure 3) indicates the unit is absolutely flat at 20Hz to 20kHz, and 1dB down at 40kHz. This test was run at 5.5V to reference the result to 0dB. The Crosstalk graph (Figure 4) shows channel-to-channel isolation right at -100dB across the bandwidth. Figure 5 shows THD+N vs. Frequency for the Danville Signal dspNexus. The last test (Figure 6) compares the IMD response of the dspNexus with the background IMD of the AP555B.
Taken together the data shows a respectable performance measured with the AP555B. This, plus a very nice feature set that will be at home in virtually any high-end hi-fi or high-end home theater system, means dspNexus is carving out a niche in high-end audio that I think will begin to decrease the industry’s dependence on passive filter design, a trend that certainly will make amplifier manufacturers happy—supplying one amp per transducer in a system design rather than just one. For more information, visit www.danvillesignal.com. VC
Resources
This is the Danville Demo Introduction at AXPONA:
https://www.youtube.com/watch?v=1WsRjR6kXik
Before the show, Tom Martin from The Absolute Sound released a Sneak Preview Video that talked about the Magnepan Open Architecture Concept Speaker working with the dspNexus 2/8:
https://youtu.be/G2aRzygAOgI?si=jqv_uwd1Rs17fM
“Awsome Demo of the Advantages of DSP and Active Crossover-Danville Signal Processing with Magnepan,” Audiophile Junkie, https://youtu.be/jzFxG8KPIEE?si=C8Qg0IbAo1d0GH-Q
“Who Were the Standouts?” Absolute Sound,
https://youtu.be/c1s12SK__j0?si=OajUnCuxnb3Jsk5f
“The Audio Belle Takes on AXPONA 2024!”
https://youtu.be/VSlHMErza1M?si=CoY0q0_gBqssNbF4
This article was originally published in Voice Coil, August 2024
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