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DEQX HDP-4 Digital Signal Processor Bought this of another SNA member approx. 1 year ago in an attempt to tame my small room acoustics and as my Duntechs are already acoustically time aligned I ended up using it purely as a EQ (and very occasionally as a DAC for the CD player I hardly use). Made a HUGE difference and to my ears was completely transparent in the signal chain however I have since moved things around and added passive traps to tame the room so this has been sitting on the self unused for the past 4 months. Units in almost perfect condition and works as intended. comes with rem
This is a fair-to-strong buy on the numbers: A$2,250 sits below the A$2,348 25th percentile and well under the A$2,566 median, so it’s priced at the low end of the recent AUD comp set. That’s not just “reasonable” — it’s a genuine value tilt, especially if the unit is complete and functioning as it should.
The HDP-4 has a good rep as a serious digital hub, with the sort of flexibility and room-correction chops that still appeal to enthusiasts who want one box to anchor a system. At this price, the upside is in getting a capable, hard-to-find piece without paying median-market money; I’d mainly want to confirm condition, remote/accessories, and any history of repair before jumping.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
DEQX is an Australian digital audio specialist founded in the mid-1990s as Clarity EQ Pty Ltd and formally established in 2001 by Kim Ryrie, the legendary co-founder of Fairlight Instruments. Ryrie's pedigree in pioneering digital audio technology—Fairlight revolutionized music production in the 1980s through its groundbreaking sampling instruments—directly shaped DEQX's engineering philosophy and access to world-class design talent. This heritage positions DEQX as a company with deep roots in digital signal processing innovation.
DEQX specializes exclusively in digital pre-amplifiers and audio processors engineered around speaker calibration and room correction. Their current Gen-4 lineup features integrated systems like the LS200 and flagship pre-amplifiers such as the Pre-8, all built on multi-core 64-bit processing architecture. Rather than traditional component categories, DEQX's core offering centers on digital correction technology that compensates for loudspeaker distortions and phase errors, reconstructing audio signals with microsecond precision to achieve time-coherent reproduction.
DEQX occupies the high-end niche market, targeting discerning audiophiles who prioritize measurement-based accuracy and digital processing sophistication over conventional analog approaches. Over 95 percent of their products are exported globally, reflecting strong international recognition among serious listeners. The brand has cultivated a reputation as a specialist tool for those viewing speaker calibration as essential to achieving reference-quality sound, positioning itself distinctly within the premium segment where technical innovation and measurable performance command premium pricing.
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