Audio-gd Reference 5 ~ A PCM1704UK-based DAC with DSP

This all started when I found Audio-gd, an audio manufacturer led by He Qinghua or well known as Kingwa. He makes superb audio gear based on designs that can only be found in some of the most exotic audio electronics on the planet. Oh, don’t worry about the price, they are very reasonable for what you get in the unit. The designer/owner himself is a very honest person which is a huge plus in my book; there are very few honest personalities in audiophile world. I’d have a hard time finding similar products that can compete well in Audio-gd price brackets or even well above it. I have had a few Audio-gd products, my newest toy from them is the new Audio-gd Reference 5 DSP.

Reference 5 idea was suggested by an audio forum member who owns a complete Audio-gd system. He suggested Kingwa that Audio-gd needed a DAC to be paired with their smallest balanced headphone amp/preamp, the ROC. The chassis was readily available. I never thought it could be done at the time as the chassis is quite small for a fully balanced PCM1704U-K-based DAC. Not only did he manage to design one, I think he brought up a few interesting ideas about the design which will be covered below.

Design

✭ PCM1704 ✭
The RE5 uses four Burr-Brown PCM1704U-K ~ R-2R/multi-bit chip, two chips per channel. It’s a fully differential/balanced DAC. The PCM1704U-K is considered to be the best sounding DAC chip. It is also the last of its kind.

✭ DSP-1 ✭
There are two kinds of Reference 5 ~ RE5. The DSP version uses Audio-gd DSP-1 and the DF version uses the DF1704 digital filter. DSP-1 is a powerful proprietary programmable digital filter processor developed by Audio-gd. Burr Brown DF1704 is a typical digital filter used in many PCM1704-based DACs. For HDCD lovers, unfortunately, none of RE5 digital filter options can decode HDCD, you would have to choose one of their DACs that is designed specifically for PMD100. DSP-1 uses Altera Cyclone on its’ heart, it has comparable processing speed to an Intel Pentium II processor. If you want to play with DSP-1 settings (switchable via DIP switches on the DSP-1 board), here is the diagram:

DAC Reference 5 has built in DSP-1 processor, which is a Two-channel Digital Interpolation Filter and data in-phase processor for digital audio. This Device offers advanced features for high-performance digital signal processing (DSP) applications up to 250-MHz. Data and Master-clock in-phase processing are without jitters. So DAC Reference 5 can offer a clear and focused soundstage, apart from accurate and neutral reproduction of the recorded disc/music. Theoretically when using the DSP1, data will be running parallel, achieving near zero jitter state, no matter the level of CD transport attached, be it hypermarket grade or hi-end level, you will still be getting the best and similar sound quality! Practically, through some experiment, although we could perceive the sound quality difference between differently priced and level of CD transports (as an audiophile, you just can’t just follow pure theory, but you must also venture the practical side too), but final result shows that using entry level CD transport or hypermarket grade DVD player, the improvement of sound quality is huge compared to typical digital processor chip like PMD-100, DF1704 etc.

✭ ACSS & Overbuilt Power Supply and Filtration ✭
All the processing/filtering after the DAC is done in the current mode ~ ACSS (Audio-gd Current Signal Sytem) which is a lot less harmful to the sound than voltage mode. Each PCM1704U-K has its’ own ACSS module. It has zero feedback analog stage, discrete output stage ~ there is no op-amp/IC, no coupling capacitor on the signal path, and all DC coupled. The power supply is monstrous, it has nine groups of parallel voltage regulators to purify dirty power and provide clean power to the digital board and analog stages. There are two beefy R-Core power transformers, each of them serves different purpose, one for the digital board and the other one for the analog stage. R-Core transformers are arguably better than torodial transformers. The transformers, ACSS modules, and IEC socket are carefully shielded with copper sheets to avoid interference. Each and every section of the DAC is heavily regulated. Those are not marketing hypes, they are just good designs.

The ACSS is a non-feedback technology made with discrete amplifiers. Most people know the global feedback design can offer better specs in test measurements, and non-feedback can’t do well in test measurements but can offer better sound for the human’s ears. Here is a conflict of the classic circuits. But the ACSS opens a new field, it can offer a least coloration sound which is more neutral with very low distortion and high linearity. So it can retain the dynamics, detail and neutral sound but not sound bright or harsh.Audio signals are usually transmitted as voltage fluctuations, such as what eventually powers headphones and speakers. Instead of this, Audio-gd gear sends the signals, including digital (a first as far as I know) as a current signal (electricity has voltage and current). The advantage is that the effects of components on the signal, including cables, are reduced considerably this way, and you end up with a cleaner signal. Also, in Audio-gd gear, after the signal is amplified, it’s changed back to a voltage signal. However, if you connect two Audio-gd components together using ACSS, the circuits changing voltage to current and back are bypassed, so both act as if they are one unit, improving things further.

✭ Modular Circuits ✭
Since the entire analog and digital circuitries are modular, users may easily replace modules in the DAC if there is any future upgrades. The DSP-1 is socketed onto the digital board and the digital board is lifted above the main PC board by three aluminum standoffs. There are two ACSS modules ‘hidden’ underneath the digital board. Recently, Audio-gd ran out of PCM2706 USB receiver, Kingwa posted an offer on Audio-gd website to exchange the USB input for another Coax or Optical input. To have another Coax or optical input, the digital board needs to be changed.

Inputs & Outputs (stock config):

• 3 digital inputs: Toslink-Optical, Coax-RCA, USB.
• 2 sets of analog outputs: RCA and XLR.
• 1 set of ACSS outputs if one wants to utilize Audio-gd’s ACSS technology. That is another compelling reason to get one of their preamps, power amps or integrated amps.

I don’t use the built-in USB input, so I won’t bother writing anything about it here. For those who cares about the built-in USB input, it uses Tenor TE7022 24bit/96kHz USB receiver. The same Tenor chip can be found in Stello U2, NuForce HDP, NuForce uDAC-2, and Teralink X2. Instead of having a USB input, my new RE5 has two Toslink inputs and two coaxial BNC inputs. I figured it would be better to have no USB input as the technology is still maturing. There are various USB-SPDIF converters out there, new ones come out every a couple of months.

Build Quality

There isn’t anything special about its’ exterior, it has an old school fairly rugged lightly brushed aluminum case with solid aluminum feet. Unfortunately, the fit and finish of the chassis is still well below my expectations. There are scratches, gaps and excess materials all over the chassis. I own a Wyred 4 Sound DAC, comparing them side by side is like comparing a Lexux Vs. a cheap Chevy. W4S DAC’s fit and finish and overall build quality are top-notch, much better than the RE5; my main beef is sub-par parts selection that do not contribute directly to the sound quality, such as: cheap CMC RCA jacks (that can easily wear out after several usages) and flimsy ACSS connectors (I may replace the ACSS connectors with mini XLR). In all honesty, they make little or no effect to the sound quality. I would rather have a well designed innards than a beautiful chassis that may cost up to half the price of the unit and skimp on the quality of the components inside. Besides, I sit at least six to ten feet away, it looks simple and fairly beautiful. Overall, the build quality of the innards is very good. It definately looks handmade.

The first thing that I noticed when I opened the RE5 was, it is massively populated and well laid out. There is practically little to no space spared. It screams great care that Kingwa has given in designing this DAC. Aside from RE5’s engineering prowess, I find many high quality components used inside the RE5, such as: Dale resistors, Hitachi transistors, Toshiba transistors, WIMA film capacitors, Solen capacitors, Sanyo OS-CON caps, WBT silver solders, Canare BNC, and Neutrik XLR. The input naming on the RE5 is simple and user-friendly. There is a switch knob on the face plate for switching between Coax, Toslink, and USB. It really is a very simple case. The chassis looks similar to a TEAC unit ~ it also has rounded corners instead of boxy looking cases like older Audio-gd gear. This chassis is also used for Audio-gd balanced headphone amp/pre amp, the Phoenix and the ROC.

Setup

All electronics are plugged onto a PS Audio Quintet power center. Quintet is the first passive power conditioner that I found to work as advertised, it cleans power and it protects any electronics plugged onto it. I’m feeding the RE5 with Squeezebox Touch and Halide Design Bridge plugged onto my Apple MacBook Air with Audirvana+). I use the RE5 XLR outputs to feed Wyred 4 Sound STI-500 (a state-of-the-art ‘wire with gain’ integrated amplifier). The speakers are Selah Audio RC3R on Sanus speaker stands. Several speakers isolation devices and room treatments are used to get the most out of the speakers. I have various analog interconnects, digital interconnects, speaker cables, and power cables but ultimately settled with Blue Jeans Cable. I have used the RE5 for several weeks to familiarize myself with the sound signature.

Now, about the Sound Quality…
It’s definitely an upgrade over my old DAC-19Mk3 ~ which beats PS Audio lower end model, Benchmark DAC, and RWA DAC in musicality. Everything seems to sound clearer and more dynamic. I can hear more passages in the music, the bass goes deeper and better tonal balance. It produces a very smooth sound signature. The sound placement is right where I want it to be which is on the center of a stage. To keep this simpler, all the good things and improvements over those DACs mentioned above are easily distinguishable. Two months ago, I went to a jazz concert in Seattle. FYI, the theatre is renowned for its excellent sound system, it’s not like your typical concert venues which mostly offer mediocre sound systems. I still remember the superb experience listening to her musics live, how good the vocal was, listening to the same music at the jazz concert with the RE5 is pretty close. I have no trouble identifying instruments that are being played, instruments sound very real, and silky smooth vocal seems to evolve around me. I’m a big fan of movie trailer musics, musics created by Two Steps From Hell, Alan Silvestri, Hans Zimmer, Harry Gregson-Williams, and Steve Jablonsky are often hard to find, a few of them are only available on iTunes. Listening to a few Steve Jablonsky’s music blow my mind, it’s so surreal! The best thing about the RE5 is that it does not get in the way of the music, it simply disappears. This is what Hi-Fi is all about.

The thing about high-end DACs is that they offer very little performance for the money. This isn’t the case with RE5 or any top of the line Audio-gd DACs. While some may not like the sound due to its very slightly colored sound signature (sometimes, it can be too smooth), I think it’s really the sound signature of this particular DAC chips. I could be wrong but hearing PCM1704 on several occasions, almost all of them sound very similar. People might say, well, the PWD is better. PWD is only better at several key areas. No DAC stands out from the rest. If you like neutral but musical sound, you might like the PWD. But for the ultimate clean musical sound, you’ll like W4S DAC-2. Now, let’s bring DAC-2 on the table. The RE5 sounds good but DAC-2 betters it in some areas, such as: soundstage, speed, details, precision. Speed and cleanliness in complex passages are the major differences here. RE5 can be somewhat slow and not as clean as the DAC-2. That does not mean the RE5 is not a good DAC. It is, it’s just it offers different presentation.

To make this simpler, here are the pros and cons:

Pros:

1. Musical
2. Vocal
3. Smooth, easy on the ears.
4. Natural, organic-sound.
5. Expansive soundstage, some people might like this.
6. Clean bass, again, some people might like this.

Cons:

1. Soundstage is not as precise as some of the best DACs.
2. Not the fastest sounding DAC.
3. Some like the smoothness, but some say it’s a dark-sounding DAC, it is.

In all fairness, without all those newer best performing DACs, this could be the end game. This could be the only DAC that you really need. After all, the goal is to enjoy music, not analyzing them. Other words, buy what you enjoy the most, not the latest DAC that you can get. Usually, DACs based on older DAC chips tend to sound better because designers have mastered making DACs around them.

~~~

The RE5 is a great sounding DAC quite possibly one of the most natural sounding DACs that I have tried. I find it a lot easier to find flaws from my previous DACs ~ the only way to compare which DAC is better than the other is compare them side by side and spend some time with them. With this DAC, I often feel very excited playing musics that I have forgotten in my hard drives ~ I find myself searching for good music again. I don’t have any genre preference, as long as the music is good and it is well recorded, I’m willing to listen to it. DACs from well-known brands are often claimed to be great bargains for the money. Some even compare them by their prices, I’ve never seen a direct correlation between cost and quality in electronics. In my opinion, most of them offer very little for the money, in fact, they are often very overpriced. I would say, the RE5 is the ‘real’ bargain for money, a genuine high performance DAC for the $$. This is definitely one of the DACs that I’m going to keep for a long time. It’s time to take a rest and enjoy the music. Happy Listening!

• Audio-gd
• DAC
• PS Audio
• Red Wine Audio

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