Last summer, while perusing the DIY section at Head-Fi.org, I came across a thread discussing making a DIY USB DAC Kit. Having built one amp (with help from my engineer brother in law) I liked to think of myself as a DIY guy, though this was clearly an exaggeration. Not having followed any of the thread or any of the discussion, I sent off an email to see if I could get one. I was told it was about $50 for the kit. I ordered one up, and when it came, I set it aside. The reason for this is that it was tiny. I had only ever soldered one thing before, and the small size of the parts was overwhelming. A few months later, I looked at all the parts and had a pang of panic that, in addition to the smallness, there were several resistors missing. I figured I was going to have to order these myself, and since it would be silly to pay shipping for less than a dollar in parts, I was going to wait until I had a larger order.

Now, it turns out that I was not missing resistors. They were there, but they were surface mount and were so tiny I simply hadn't seen them. Further, they were not the smallest thing needing soldering. The DAC chip itself looked daunting, so again I set the project aside. After about 4 months of this, I decided that either I was going to pitch the thing without trying and thus have no USB DAC, or I was going to destroy it while attempting to build it, maybe learn something in the process, and be no worse off. It honestly didn't occur to me that I might get it working.

I finally got the thing built -- it turns out that surface mount stuff is a lot easier than it looks -- and when I plugged it in, it worked. I must say, too, that the moment it worked was the moment I actually became a DIY guy. I figured if I could build this thing, I could build anything. So, now that I have been playing with it for a few months, I thought I'd review it. It should be noted, however, that these seem to not be available in a full kit form anymore. They are available as a partial kit for £12 each + £3 flat rate shipping to the US with everything except the IC's. Thus, it will cost you about $25 plus tracking down 4 chips which will cost about another $25. Three of the chips are made by TI, and thus may be available through DigiKey. The fourth is from Maxim, and everywhere I have seen it there has been a minimum order qualtity of 2500, so be sure you can get the chips before ordering the kit.

To review the Guzzler USB DAC (henceforth called the GUD) I am going to compare it to two computer based systems. The first is an M-Audio Sonica running through a Monarchy DIP into a Cal Audio Sigma DAC with a Mullard tube (I'll refer to this as the Cal.) The last is the same Sonica + DIP but with the decoding done by a Cary 303/200. Thus, all of these systems are USB audio systems. The Toslink connection from the Sonica to the DIP was via a Monster Toslink cable. I used a DIY Coax digital cable from the DIP to the DACs. Initially, I intended to compare the Sonica alone in addition to a Xitel USB DAC, but it turned out not to be worth the trouble. The Guzzler USB DAC puts these two options to shame. Other associated equipment is a DIY Pete Millett headphone amp powered by a STEPS PS and a set of Grado RS-1's. The USB DAC is hardwired into this amp with about 6 inches of Kimber TCSS. The other DACs were connected with .5 meters of Cardas Neutral Reference cables (and for what it's worth, the connection from the input jacks on the amp to the PCB is a 12 inch run if Kimber TCSS.) (A note about my USB DAC: I assembled mine to be powered off the 5V supplied by the USB cable. The DAC's designer claims that this setup is noisier than powering it with batteries, but I have not noticed noise to be a problem, in fact, the thing is silent.)

As a bit of background, the GUD is a USB based digital to analog converter. It is based on the Burr Brown pcm2702 chip. There is no digital output, no spdif input, no analog input. While this presents some limitations in the GUD's usefulness, as we'll see below, the DAC sounds good enough that it is not that much of a limitation.

The Sonica through the Cal has been my reference office computer system for a while. In particular, I like the tubey sound from the Cal. This always surprised me. Years ago, when auditioning audio equipment, I remember thinking that Cal stuff was too bright, too nasal sounding, and all around not to my liking. So, when I picked up the Sigma on the used market (the Sigma was a flavor of the month around Head-Fi about a year and a half ago) I was amazed that I liked it at all (though, with the stock tube it was a bit bright.) But, compared to what I had been using before it -- a Rotel 855 from 1991 -- the Cal was open, airy, and full of tube goodness.

So, how does the Guzzler USB DAC compare to the Cal? It's not even close. This may be in part since I am listening through a tube amp and thus I don't need the tubes in the Cal, but the GUD does almost everything better. It is interesting, because it does them better not in the way where you think, "well, the bass is more defined, and the mid range is more liquid," though both of these are true. Instead, the GUD sounds good, and after listening to the GUD, the Cal does not. Perhaps the best way to quantify the difference is that the GUD sounds better than the Cal in the way that Grado RS-1s sound better than SR-80s. It reminds me that in the past, when I auditioned Cal equipment, it was always alongside Audio Research (which the dealer also sold) and this may be why I was so averse to it.

Anyway, what I notice in the GUD as opposed to the Cal is that it is more neutral. Actually, the GUD is slightly on the dark side of neutral. It has deep bass that is more or less under control. It covers all of the frequency range, the top is pleasant, and dynamics are very good. It is also quite laid back. There aren't any audible humps or bright spots, and nothing is in your face. Perhaps most importantly, the resolution is quite good. How good? Well, the difference between a FLAC file and an MP3 encoded at 320 is obvious. All the little things come through, though they don't overpower.

Now, I don't want to mislead. The GUD is not perfect. To prove that to myself, I compared it to my Cary 303/200. The difference, however, is not quite what you might think. It isn't that the sonic signature is all that difference. It is that the Cary has that extra kick that says it is high end. Essentially, as far as things like bass, midrange, pace, and the like, the Cary is a bit better on all of them. With the GUD you hear everything and it sounds good. With the Cary, you float. The music envelopes you, and you stop hearing the equipment at all. So, for example, on something like Cat Power's Sweedeedee, with the GUD her guitar sound full and round. With the Cary, it is in the room with you.

As for resolution, though, as I said, the GUD is good but the Cary is in a different class. For instance, on Emmylou Harris's Wayfaring Stranger, the GUD does not quite get the thump of the bass and the separation between the voices and the instruments that the Cary does. It does, however, convey the music in a convincing way. For another example, on Felix Da Housecat's Madame Hollywood, with the GUD you can hear some faint scratching in the right channel. With the Cary, it is clear that it is surface noise from a sampled record. The GUD never gets to this level, but it also only costs 1/60th as much, so there is no shame in that.

Additionally, compared to the Cary, the GUD has a bit of harshness in the upper mids. This is particularly true on very hot recordings. The Cary is able to control this, but the GUD does distort ever so slightly.

Last, the soundstage of the GUD tends to be very far back in the speakers. The Cary is famous, or notorious, for its soundstage. While it is not hugely deep, it is wide and spacious, extending well beyond the speakers on either side. With headphones, this soundstage translates into being all around your head -- even with Grados. It does not feel confined, but is instead all over. The GUD's soundstage, on the other hand, is back. It begins and ends behind the Cary's. For headphones, particularly with Grados, this is nice because it does not localize in your head. With more laid back phones -- I tried it with AKG 401's -- it can start to lack some oomph and pace due to this recessed sound. This is in some sense also due to the amp used which is itself very laidback and relaxed. It does suggest, however, that if you are looking for in your face sound, the GUD will need both phones as well as amp to be a bit on the forward side. If, however, you are like me and your tastes are such that you view Krell amps as expensive doorstops, you may find the GUD to have just the right balance.

There is a last issue that is worth exploring which is that since the GUD is using the standard USB audio driver, the computer is resampling to 48khz. With the Sonica into the Cary, one is able to get bit perfect output. So, in some sense, the comparison is unfair as the two DACs are decoding different bits. However, since the GUD does not give an easy option to correct this, one must accept the limitation. Just in case this was the difference, I also ran a Xitel soundcard, which uses the standard USB audio drivers, into the Cary. The Cary did sound slightly worse than it had, but it was still better than the GUD. What this means, however, is that if you want to squeeze every last bit of performance out of the GUD, you should find a way to get bit perfect output over USB (there seems to be some discussion that this is possible with Linux, but I have not followed the discussion closely enough to know.)

So, all in all, I am not getting rid of my Cary anytime soon, but I am enjoying the GUD quite a bit and not feeling like I am missing out on anything. For $50 and a little work, it is easily the best money I have spent in audio.

Oh, there is one thing to know which is that there seems to be a bug somewhere in the GUD. If the voltage drops too low, it starts spewing out white noise. This happened with one computer of mine where the USB port was in a PCI card. When using the USB port built into my laptop, I have not had a problem. Others, using batteries to power the GUD, have reported that when the battery gets too low, the DAC does its white noise thing.

The DAC is available direct from guzzler on Head-fi.org [awjl3 (at) cam (dot) ac (dot) uk] as a partial kit for £12. The kit contains everything you need except for the Burr Brown chip, 2 TI voltage regulators, an IC from Maxim, RCA's, solder, and a case. Schematic and details available from http://www.mellowparenting.demon.co.uk/guzzler/usbdac.html.

Last Edit: 02/10/2005