The GW Labs DSP Digital Signal Processor

The GW Labs DSP Digital Signal Processor

Henry Wilkenson

10 April 2002


6.6″W × 7.5″D × 2.25″H
Weight: 3 lb.
Inputs: Optical (Toslink), Coaxial (RCA) or Balanced (AES/EBU)
Outputs: Coaxial or Balanced
Warranty: 2 Years Parts and Labor
Price: $399.00

Centasound International Inc.
P.O. Box 210337
San Francisco, CA. 94121
Tel: (415) 668-9003

I have to admit that vast improvements have been made to the sound quality of digital devices since the early eighties. If you remember, that was when we were promised “perfect sound forever”, from the proponents of digital audio. Back then, there was quite a difference between the promises made regarding sound quality and what was actually delivered. While today’s digital equipment sounds quite good, I understand why there are still so many LP adherents. Fear not, I have no intention of opening that can of worms here.

Basically, there are two approaches to creating a digital front end. The simplest, of course, is the one box CD player. Because audiophiles are predisposed to tweak and tinker, many will choose the second approach, namely, the outboard DAC, power supply and transport. While this method will arguably result in better sound, it requires much more care in the selection of the components. Then there is the need to select the appropriate digital cables. Naturally this more difficult route is often more attractive to audiophiles. I believe there is sufficient evidence to support the proposition that when it comes to audio, the more difficult something is, the more audiophiles will embrace it. Yet, merely selecting a multi-component digital front end and going through all of the effort and trouble to set it up properly, it still is not a given that you will wind up with better sound.

As many of you already know, when using a separate DAC and transport, one of the biggest problems you are likely to encounter is that of clock jitter. This occurs when there are variations in the clock timing the reconstruction of the digital audio samples. There are several devices on the market designed to address this problem. One of the best known of these products is the well-regarded Monarchy Audio Digital Interface Processor. The Monarchy “Jitter Box” is a very effective jitter-reducing device that is used widely by many audiophiles. The GW Labs Digital Signal Processor, or DSP for short, is not simply a Monarchy jitter box under a new name; it goes far beyond that, as we shall see.

The DSP, though it is a jitter reduction device, offers several important differences. It is also a digital-to-digital upsampling processor that converts any PCM (Pulse Code Modulation) digital signal with sampling frequencies ranging from 32-96 kHz to 44.1 or 96 kHz. According to product literature, when the DSP is inserted between a transport and a DAC, it will enhance the digital signal and output a cleaner digital signal to the DAC. The reason is partly because the signal coming from the transport is boosted ten times. The DAC will then see a strong and steady signal. It is further claimed that this unit will enhance the sonic performance of any DAC. While many DACs cannot handle an upsampled 96 kHz signal, GW Labs claims that the sound will also be enhanced at the standard 44.1 kHz sampling rate. Their literature goes on to state that the best performance is obtained at the 96 kHz setting. Regardless of what sampling rate is chosen, there is a constant bit extension from 16 to 24 bits, handled by a Crystal Semiconductor device.

Multiple filters are used to suppress any noise that is generated within the unit and to prevent any AC noise from entering the circuitry. Over engineered power supplies using separate transformer windings feed two low noise rectifiers which are followed by choke-filtered capacitor banks. Each bank contains 20,000 µF of filtering capacitance. Considering how important the power supplies are to any audio component, it is very good to see this kind of effort being made to get them right. It is unusual for such a robust design to be employed in a unit retailing at this price point. It should be noted that the unit takes from 50 to 100 hours of actual use to burn in. While the unit that I had sounded good right out of the box, the sound steadily improved with use.

The DSP is both a well constructed and, I think, a visually appealing component. The front panel has toggle switches for changing the sampling rate from 44.1 to 96 kHz and between the optical and line inputs. In fact, you can have both the line and optical cables attached to the unit at the same time. This feature will make cable comparisons very easy to make. There is a small green light on the front panel that lights when the unit has locked onto the signal coming from the transport. The rear panel sports what appear to be very high quality RCA and balanced inputs. You will find an IEC connector for connecting a detachable power cord there as well. There is no on/off switch since the unit is intended to be on all of the time.

Use and Listening

I found the DSP to be a very easy component to set up and use. While the instruction sheet is a simple two page double-sided affair, it will provide all of the information that you will need to install and begin using the unit.

If you are using the Art DI/O DAC as I am currently, the trick is to make sure that the DAC has locked onto the signal from the DSP. This can be a little tricky until you become used to it. After starting the transport, I unplug the power supply to the DAC and plug it in again after about ten seconds. In effect, this re-boots the DAC. Once this was done, the DAC locked onto the signal and from that point everything went smoothly.

As mentioned earlier, it is very easy to toggle between the 44.1 and the 96 kHz sampling rates. At the 44.1 setting, I did notice a slight improvement in ambient information. I could hear more of the cues that give you a sense of the size of the recording venue. There was also a slight increase in the amount of air between the instruments on some recordings. This effect varied from disk to disk. As you might expect, the improvements were greater with material that was really well recorded.

When I switched to the 96 kHz-sampling rate, I heard a much greater improvement in soundstage dimensionality and focus. There was an increase in stage layering from front to back. Low level details became much clearer while remaining in proper perspective relative to the overall sonic picture. I noticed a greater sense of openness. The music seemed to be coming from a larger source. It’s as if the performers suddenly moved into a larger recording hall or studio.

There was also an increase in extension at the frequency extremes. The bass was deeper while maintaining its tunefulness. That see-into quality was improved throughout the spectrum. The greater sense of ease that the music took on was quite enjoyable. In short, the benefits of this higher resolution made themselves known quite clearly. The down side of this is that poorly recorded CDs will be revealed for what they are. Anything that is harsh or hard sounding will come across that way. Dexter Gordon’s “Tanya,” from the CD,Dexter Gordon, One Flight Up [Blue Note CDP 7 84176 2] is a recording where the recording engineer’s hand is clearly audible. Dexter’s sax is in the left channel toward the rear of the stage with an echo around it and the drummer is far right and forward. When Donald Byrd comes in on trumpet, the sound is somewhat bright and very forward. I found this balance to be more pronounced with the DSP in the system. Higher resolution can be a double-edged sword.

Some of the newly remastered CDs, especially some of those from Blue Note, tend to be very hot to begin with. The DSP, when combined with my DAC, can really cause the music on these recordings to be in your face. While not from Blue Note, one CD in particular comes to mind, The Best of the Temptations, Volume 1- The 60’s [Motown 012 153362 2]. This is a great Motown reissue, but it is really, really hot. While listening to this one, I have to keep the volume so far down that it was almost off. I attribute this situation more to the very high gain of my DAC, rather than to the GW Systems DSP. The DSP, though, is also contributing somewhat to the situation. However, this is only a problem with a few CDs.

Since the DSP boosts the signal, any DAC that has a very high output might overload some line stages. If you are currently operating near the overload point of your line stage, this unit might put you over the limit. This may or may not be a problem, depending on the particular line stage that you are using.

Since the unit is so small and lightweight, it was very easy to carry around and try in other systems. Jimmy Marks is a friend and fellow audiophile who was willing to give the DSP a try. We are using the same DAC but his system consists of tube gear and Magnepan speakers. At the 96 kHz setting, the DSP provided the same improvements that I described earlier. Given the characteristic speed and transparency of the Maggies, the improvements were even greater than I was able to achieve in my system. This audition has resulted in Jim placing an order for the DSP.

GW Labs has come up with a product that addresses some very real problems quite effectively. While I found the 44.1 kHz setting made subtle improvements in my system, the 96 kHz setting is where the full capability of this DSP is realized. While $400 is not a great deal to pay for a component in the realm of high-end audio, I found it a reasonable price given the level of performance that the DSP offers.

I have one final caveat to share with you. The GW Labs DSP has been designed to work only with two channel stereo reproduction. If you wish to enhance the performance of a home theater set-up, I am afraid that you will have to look elsewhere. The unit simply will not work with Dolby Digital or DTS units.

My advice is always to try before you buy whenever that is possible. In this case, you have thirty days to decide whether you like the unit or not. If you decide to return the unit, you will be charged a 15% restocking fee. According to my sources, precious few of these units have been returned. It appears that GW Labs has scored a solid hit here with the DSP.

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