PS Audio's excellent webpage neatly illustrates the point that the company has been making DACs for a long time, 21 years in fact. Although the brand's distribution has been sporadic in the UK, you may remember the debut of its 'Digital Link' - one of the first DACs to hit the market.
Back then, DACs were just about the only way a small manufacturer could make his mark in the digital world. Nowadays, the main attraction with a DAC is the possibility of upgrading more than one digital source.
Take computers, for instance. They're becoming more prevalent in the domestic audio market but need some attention to achieve the best results. Something that the most recent successor to the first Digital Link; the DLIII, can accomplish thanks to the addition of a USB input, alongside the familiar electrical and optical S/PDIF connectors.
Some computers do, of course, have a digital output but its data are often impure, having been through sample-rate conversion using devices not exactly of audiophile standard. Professional digital output cards aren't particularly expensive but it's all extra hassle, and practically everything sold in the last four or five years features USB.
We've had limited experience of audio via USB, but the DLIII did the usual USB thing of installing itself on first connection, with USB appearing as an option in the relevant bits of Windows applications, and everything worked as one would wish.
On the audio quality side, PS Audio makes much of the DLIII's ability to upsample to either 96kHz or 192kHz, selected by the user at the front panel. The whole business of upsampling and oversampling is a complicated and often misleading one, but at the very least the ability to compare different upsampling rates like this is going to be interesting and, possibly, very useful. Upsampling is performed by a popular high performance asynchronous chip; the SRC4192, which also makes the DAC tolerant of poor-accuracy digital sources - including all too many computers.
Other internal parts include a recent DAC chip with excellent specifications, as well as input receivers for S/PDIF and USB. The power supply is generous, with a large toroidal transformer (modestly rated at 32VA), fast rectifier diodes and more smoothing capacitors than you'll find in most medium-power amplifiers.
Most components are surface-mounted which makes the circuit hard to examine, but PS tells us that the important current-to-voltage stage that follows the DAC chip uses a transistor rather than an op-amp. The use of the latter has been associated with distortion caused by the exceptionally fast-moving signals that have to be handled at this point in the circuit and, while there are ways of mitigating that, PS Audio's approach has plenty going for it.
On the basis that most DLIIIs will probably spend the majority of their time converting data from CDs (a more critical application than being connected to computers and other sources) we did most of our listening under those circumstances, partnering it with a number of more or less fancy transports. As one would hope, the transport proved to make quite a small difference and so the comments that follow should be generally applicable.
The strongest suit this DAC has to offer is its bass. Here, extension, precision and tunefulness combine to make for a vigorous and thoroughly lifelike lower register in any style of music. This provides a great grounding for the rest of the sonic image to grow from and is equally welcome in rock, jazz and classical recordings.
There's nothing like a good solid, clean bass register to encourage loud listening and, on the whole, that's a gratifying experience with this component in the system. All the same,
we did feel that. once or twice, it's a little inclined to shout in the upper midrange.
In fact, that is just one symptom of the DLIII's weakness, something which on balance we found only a mild drawback, but certainly worth reporting. It tends to suffer from some slight confusion and congestion in the midband, a lack of precision and grip, which is an unfortunate blot on an otherwise very clean slate.
High treble is very clear and beautifully extended, with plenty of sparkle and a natural acoustic decay and the lower parts of the midrange are also good - frequencies up to the higher end of the female singing register. Above that, things become just a little less well defined and, if anything, the DLIII's success at the frequency extremes throws this into sharper contrast.
Perhaps, surprisingly, this DAC seems very confident with music that exists mostly in the midband: simple voice and one or two instruments, for instance. If one is to be really fussy, there's the tiniest hint of congestion, but in isolation it's not something one would be likely to spot.
It's in rock and other lively, upbeat music that the midrange congestion becomes most marked, with a lessening of the involvement that a well-produced recording can bring to a listening session. One might think that such music, with its notorious reliance on overdriven guitars and other such 'distorted' sounds, would be most forgiving but it's not always so!
If that's all rather picky, we've little cause to criticise the DLIII when it's part of a computer-based system. Of course, it is being compared with what is typically a hamstrung bit of audio electronics at best. Even MP3 files and internet radio stations (the better ones) benefit quite markedly and losslessly stored files improve even more.
Where we don't find the improvements outstanding is with DAB digital radio. Most hi-fi DAB tuners have a good internal DAC already and it's in the nature of data-reduced formats that they make the differences between basically decent DACs and audio stagesless obvious. Still, you could use something like a PURE DAB table radio (they mostly have a digital output) to the latter's advantage.
The measured showing of the DLIII is fine apart from a little jitter (apparently internal as it varies little with source performance), which may well account for the slight congestion. There's practically no difference between its 96kHz and 192kHz performance, which probably explains why we couldn't reliably hear any. Overall, it is a handy product of good but, perhaps, not outstanding performance.