The DEQX HDP-3 Preamp Processor

by admin on April 12, 2011 · 12 comments

in Digital, Preamplifiers, Star Components

by Martin Appel

I saw a prototype unit of a new, improved DEQX Processor at CES 2009 and asked Kim Ryrie that if this new model went into production, I should review it. Back in June 2006, my review of his first model, the 2.6P, appeared in these pages and proved to be a revolutionary product which I own and plays a central role in my system. In that review I explained how the DEQX worked and what its capabilities were, as well as the reasons its use would greatly augment the sound of any system.

The new processor, the HDP-3, has arrived, as well as a scaled down model, called the HDP Express. The HDP-3 arrived with the Jenson/DEQX transformer analogue balanced outputs (6 x XLR) option. The standard unit comes with 6 RCA unbalanced outputs. I’ll be reviewing the HDP-3 and fellow Audiophilia staffer, Mike Levy will be reviewing the Express.

To reiterate, the DEQX has three main functions: it’s a speaker corrector, a room corrector and active steep slope crossover network. Additionally, it can be a real time equalizer (via the remote control or computer) and contains a superb DAC. For a complete description of its technical capabilities, specifications how all this is achieved see my 2.6P review and read Kim Ryrie’s description on the website. What follows is a brief description of how one would use the DEQX.

In a typical stereo system, the speakers contain internal crossover networks, and the DEQX is installed between the preamplifier and the amplifier. (The DEQX could also serve as the preamplifier since it has two analogue, two digital inputs and volume control).

First, load the supplied DEQX CD into your computer. Then an optional microphone (there are two microphone packages available) with cable is connected to the DEQX and an included USB cable is also connected from your computer to the DEQX. The next step is to set up the microphone about 1 meter from the middle of your speaker. The instructions in the manual are well written and comprehensive. You’ll need a mic stand for this which is not supplied. It is important that you bring the speaker as far away from any walls as you can so the microphone only reads direct sound and minimizes the effects of any reflected sound. A frequency sweep test tone is produced that the computer graphs of the full frequency response of the speaker. You’ll observe all kinds of squiggles, peaks and valleys far from the neutral axis. You then apply the ‘corrective’ filter and, voila, you have a flat response. You should do this for each speaker even though they’re supposed to be identical, they usually are not. There are infinite adjustments available and you can tailor the sound to your preferences.

Once you’ve corrected your speakers you can perform a similar process for the room equalization. We all know that the acoustic impact of the room on the sound of your stereo is enormous and can have a deleterious effect. Place your speakers in their normal listening position and place the microphone as close to your listening position using the mic stand. Then, another frequency sweep test tone is generated and the graph produced will show you the irregularities, or more properly, the sonic properties of your room. In my case, there was a bass hump at around 50Hz which interfered with midrange performance. Also, adjustments needed to be made in the 9-10,000Hz area that had a large impact on the soundstage and transparency of the system. The program handled the adjustments beautifully and the improvements in the sound were immediate and illuminating. I’m getting a little ahead of myself.

In my set-up, I was able to take full advantage of the HDP-3 by using the steep slope active crossovers in the unit. My speakers, the Levy Acoustics FRM-1’s (previously known as the Wasatch Acoustics MUSINA), were designed specifically to be used with the DEQX and contain no internal crossovers. Thus each driver of the two-way speaker requires its own amplifier, 4 channels of amplification in a two-way system and the crossovers provided by the HDP-3. The DEQX contains a third set of outputs for each channel, with accompanying crossovers, for either tri-amping a pair of three-way speakers or adding a pair of subwoofers to a two-way system.

After living with the 2.6P for almost 5 years I was very familiar with its properties, so the big question was how the new model compared to the 2.6P and what the differences were between the two. Onward.

First, the casework has improved. It is twice the height as the 2.6P, allowing a little more room for connecting those high end audio cables and it’s construction out of heavier gauge metal, is a step in the right direction, as well. It comes in black or brushed aluminum.

The HDP-3 operates throughout at 24-bit / 96kHz and uses SHARC’s 32-bit floating point DSP’s from Analogue Devices that provide 160db of internal resolution. The HDP-3 also incorporates analogue power supplies, as well as six 256-step resistor ladder volume control chips and other circuit enhancements that resulted in furthering the unit’s performance in areas of transparency, sonic purity and minimizing, even further, the already low levels of distortion.


I set up the system with my Marantz SA-7s1 SACD/CD player out-putting digitally directly into the DEQX via SPDIF outlets with the ANTIPODES KOKIRI digital interconnect. I also tried using the analogue connections into my Marantz SC-7S2 preamplifier. The DEQX takes all analogue signals and converts them to digital, where all the processing happens, and then back to analogue to continue to your preamp/amp combination. By removing the internal DAC of the CD player from the audio chain, an entire step of processing is eliminated, reducing the chance for negatively impacting the sound. It works. It did sound better this way. I highly recommend that anyone using the DEQX connect their cd player digitally. If SACD’s are your source, you’ll have to connect to your preamplifier directly in analogue. The HDP-3 doesn’t handle SACD.

I allowed for at least 100 hours burn-in before I began this evaluation and realized immediately that the HPD-3 was a significant improvement over the 2.6. My overall impression was that of more solid, three dimensional images, greater transparency, an increase in soundstage depth, with more inner detail and resolution. And at the same time smoothness and liquidity were maintained. The presentation seemed more natural and relaxed. One of my reference CDs, Frank Sinatra’s SINATRA SINGS FOR ONLY THE LONELY on Capitol exhibited these features in spades. His voice had all the timbral qualities, but was now exhibiting more inner texture and greater presence then I’ve heard before. Nelson Riddle’s arrangements were clearer than ever. Instruments appeared in three dimensional space, sounding more natural and lifelike with more body.

Another reference, THE ALTERNATE BLUES- Pablo OJCCD-744-2 Clark Terry/Freddie Hubbard/Dizzy Gillespie/Oscar Peterson has three of the legends of jazz trumpet playing on display. On cut three, Dizzy opens with a soaring solo w/mute that can be very ‘hot’ and piercing. With the HDP-3 in the system you had the full horn dynamics with the mute’s contribution handled without what could have been an overly shrill presentation. Each of the players came through with greater definition, more brassiness and three-dimensionality that made the evaluation a sheer pleasure. When Hubbard soloed the space of the recording venue was even better defined then with the 2.6P. The depth and height of the space were clearly presented and the reverberant sound off the back wall was in full force. Smiles, all around.

The Telarc SACD-60575 ORFF: Carmina Burana-Runnicles/Atlanta Symphony Orchestra and Chorus, another reference that really tests a system’s ability to deliver large scale dynamics as well as resolving power. With the orchestra and chorus going at full blast, the excitement was palpable. I was hearing the individual voices of the choral members and more easily identifying the different choral sections while the orchestra was even further revealed making the experience closer to the live event. The new DEQX was performing exceptionally well.

For some kick-ass blues, I chose Stevie Ray Vaughn’s CD, STEVIE RAY VAUGHN AND DOUBLE TROUBLE-THE REAL DEAL: GREATEST HITS VOLUME 1. Cut 8, TIN PAN ALLEY, blows me away. His playing is extraordinary and the slow, powerful driving rhythm draws you in and kicks you in the gut. Once again, the HDP-3 does a better job of presenting the reality of musicians in space and SRV lives again. He explodes in my listening room and his guitar jumps at you with full dynamics and definition.

I could go on and on about different musical performances but its all about and how the HDP-3 brings them to life and manifests itself by giving the listener a more intimate connection with the music.

Nits to Pick

On a unit that has a volume control I would like to see a numerical indicator in half or full dB increments in lieu of the provided changing color volume indicator light that at best is imprecise. Even though the chassis height was doubled, the space for making connections really hasn’t appreciably grown and it can be tight connecting with today’s fat interconnects. Finally, I would still like to see a further improvement in the chassis robustness. As I said earlier, the HDP-3 represents an improvement over the 2.6P but I’d like to see it go even further.


The bottom line is that Kim Ryrie has improved an already outstanding product and created one that blurs the line between digital and analogue. Detail without edginess, unbridled musicality, transparent, dynamic and a level of involvement with the performance that is simply stunning. I’ve tried to describe, using some of our audiophile terminology, what one hears with the HDP-3 processor in your system and words don’t do it justice. It behooves you to try one — once in your system, you won’t let go. Removing it from your system will return you to a duller, two dimensional stereo that’s lost its magic. My system would be lost without it.

Give that man an Audiophilia Star Component Award.

[It is with great pleasure that we award The Audiophilia Star Component Award to the DEQX HDP-3 Preamp Processor. Congratulations! - Ed]

The DEQX HDP-3 Preamp Processor

Manufactured by DEQX PTY Limited
Unit 1, 1 Roger Street, Brookvale, Sydney NSW 2100, AUSTRALIA
Tel: +61 2 9905 6277
Fax: +61 2 9905 8066


Standard HDP-3: $3,995.00USD
Balanced out ‘active’ module (6 x XLR): $455.00USD
Balanced out (6 x XLR): $988.00USD
Standard microphone calibration kit: $279.00USD
Reference microphone calibration kit: $935.00USD

Unit as reviewed: $4,983.00USD + shipping

Manufacturer’s Comments

Dear Martin,

Many thanks for the excellent review of the HDP3.

The key feature of all DEQX processors is their ability to anechoically measure and then correct the relatively dramatic timing and phase errors that occur to different degrees for different frequency groups. Only loudspeakers introduce these errors to an alarming degree compared to the signal driving them. These ‘slewed’ timing and phase errors detract from the original musical coherence in similar ways to loudspeaker coloration caused by inaccurate frequency-response.

For example, the plus/minus 3dB error (a 6dB window of error) that passive speakers can usually achieve is typically reduced to a one-decibel window of error using the HDP3 (and HDP-Express). Timing and phase errors are also corrected roughly four-fold. So the result will nearly always be a very obvious lack of coloration and time smearing.

The nit picking is taken on board. Unlike the development cost of most high-end audio products, the HDP3 includes a very large investment developing its nearly 500,000 lines of software for over a decade. That cost has to be managed without blowing the product cost out of the water for little or no performance gain. The HDP3 is certainly up-market compared to previous models, but we will keep your comments in mind.

By the way, since your review we have announced a new service in the USA to assist users with any setting up help they might need. This is managed from our Denver support facility, where real-time on-line software control of your project is available. Support or training packages start from $295.00 USD.

Kim Ryrie

Associated Equipment

Amplifiers: 4-Hephaestus HMA-1000 Monoblocks

Speakers: Levy Acoustics FRM-1

Preamplifier: Marantz SC-7S2

Phono Preamplifier: AQVOX 2 Ci Mk II.

CD source: Marantz SA-7S1

Analogue source: Avid Volvere/SME IV arm/
Cartridge: Shelter 7000

Speaker cables: Acoustic Zen’s Absolute, Wasatch’s Ultama (no longer being produced)

Power Cords: Kaplan GS Mk II, Acoustic Zen Absolute

Interconnects: Antipodes Audio KOKIRI and KOMAKO, Acoustic Zen’s Absolute.

Accessories: Herbie’s Audio Lab Tenderfeet, Soundcare products, Acme Audio Labs wall outlets

Surge Protection: Brick Wall 2R and 8R Surge Protectors

Power Conditioning: PS AUDIO Power Plant Premier

{ 1 trackback }

The DEQX HDP — Express Processor — Audiophilia
05.18.11 at 8:00 am

{ 11 comments… read them below or add one }

Massi Takeda 04.18.11 at 6:08 am

Dear Martin,

I am writing on behalf of Mr. Nobuyoshi Kurihara Who is a importer of DEQX in japan with background of the chief sound engineer of NHK ( BBC equivalent of Japan). He has been retired from it now and started his own company. He has developed digital level meter to be used with DEQX . He felt such device makes DEQX more useful just as you felt so if you are interested in it please open Mr. Kurihara’s company website.

admin 04.19.11 at 7:36 am

Great review, Marty. Looking forward to hearing the system in June.

Readers, Mike Levy’s review of the HDP Express will be up soon.

Cheers, a

martin appel 04.22.11 at 1:19 pm

Hello Massi, I would be interested in trying it and reporting on its effectiveness. Please have him send me one.
Thank you

Massi Takeda 04.25.11 at 1:40 am

Dear Martin,

Mr. Kurihara will put it together as it is out of stock now. It will take about four weeks before he can ship. In the mean time please advise the shipping address.

Martin Appel 04.25.11 at 4:14 pm

send me your email address and I’ll send mail info

Massi Takeda 04.25.11 at 7:27 pm
Nyal 04.26.11 at 1:54 pm

Could you explain a little about this digital level meter? What does it do?

Martin Appel 04.28.11 at 3:32 pm

hi nyal, apparently it offers a visual, numeric read out for the volume level. the website’s in japanese but it looks to be in 1/2 db increments?

Paul 04.20.12 at 3:52 pm

Very informative review. How well does the HDP-3 handle phono? Is the A-D conversion fairly transparent?

Art Miller 05.06.12 at 11:10 am

I too am interested in the A/D performance and a comparison to the Express version. Anyone compare the A/D to straight in analog, that is a bypass of the unit?

MARTIN APPEL 05.08.12 at 10:22 am

In response to the A/D conversion. First I want to thank you for your interest and hope I can answer your questions. I use my Marantz preamp to handle my analogue inputs and that goes out to my DEQX. I’ve always been able to discern differences when changing cables and phono preamps very clearly and this would indicate to me that transparency is not an issue. I’ve never done a direct A/B comparison with the EXPRESS and the HDP-3 but my colleague, Mike Levy has and he feels that the EXPRESS is very close to the 3. Maybe as close as 90-93% . I hope I’ve helped.

Leave a Comment

You can use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>