July 2006

Hagerman Technology Chime Tubed 24-Bit Oversampling DAC With USB Interface
Review By Scott Faller
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  This article falls in line with my ever widening curiosity of the computer based audio revolution that is currently at hand. As I've gotten deeper and deeper into the extremely high quality sounds of computer based audio, I've been on a mission reviewing computer based interface devices and DAC's.

As you will remember, the last article I wrote covered a pair of excellent sounding, ultra-affordable, non-oversampling DAC's from Mhdt Labs. Prior to that, I covered the phenomenal sounds of the Bolder Cable modified Squeeze Box 3. This go round, I've chosen an oversampling DAC that not only features a standard S/PDIF connection but it also sports a USB interface so that you can connect it directly to your music server.

To the kit builders out there, Hagerman Technology is another one of those well known companies that offers kits and half kits for those of us hobbyists who thoroughly enjoy the feeling of accomplishment in building audio gear ourselves. Some of HagTech's better known kits are the HagUsb (DAC), the Bugle phono stage, and the Cornet phono stage.

Over the years, Jim Hagerman has built up quite a following with his ultra affordable, good sounding kits. Check any of the audio bulletin boards out there and nary a week goes by that somebody doesn't mention one of Jim's creations.

After reading so much about his designs on the boards and after listening to couple of pieces a few of the local guys had built (the Coronet sounds really good BTW), I decided to contact Jim and see if he wanted to do a review of his new Chime, SPDIF/USB tubed DAC.

To Build Or Not To Build, That Is The Question

Yes, it might have been nobler to build the unit I'm currently listening to, but I guess the wires got crossed somewhere in all the emails Jim and I traded. You guys know I love to sniff solder fumes every chance I get but when I received a well packed box from sunny Hiwa'ii, I discovered that Jim mistakenly sent me a fully assembled unit.

Actually, as I think about it, that may have been the best thing for reviewing purposes. This way, I get to listen to a bone stock unit. No cottage industry parts, no nifty wiring or really expensive RCA connectors, no builders pride of doing a good job to taint my views, just ready made tubed DAC. The only thing I can do is swap tubes. Hopefully by the end of this article, you guys will know exactly what to expect if you decide to purchase the Chime either fully assembled or in a half-kit using stock parts from Digikey (or your favorite parts supplier).

Construction

On the Hagerman Technology website, Jim really downplays the aesthetics of his creations. He claims he doesn't offer artwork, just decent cases and good solid design. To a certain extent, I agree (speaking of the cases). On the other hand, the only thing that I see that looks ‘inexpensive' on the Chime are the knobs. Heck, if you wanted to upgrade the appearance of the Chime it would only cost you about ten bucks you can find at least a dozen places online that will sell you nearly any flavor of knob your could desire.

The casing on the Chime is a nice, heavy duty, extruded piece of sheet metal that has been finished in black. The side panels are louvered to allow ventilation within the casing. Again, nothing fancy but I think it looks good sitting right next to the rest of my black gear. On the bottom of the Chime are some standard rubber, stick on feet.

Inside the Chime, Hagerman uses high quality fiberglass epoxy FR-4 circuit boards with plated through holes. The opposite side of the PCB is used as a grounding plan. According to Jim, this grounding plane is actually configured in a Star grounding pattern so well known to the DIYer. The parts HagTech has chosen for the stock build are of nice quality. The electrolytics are Nichicon, the output coupling caps are MIT and the bypass caps are Panasonic ECG metalized polypropylene. The resistors are standard metal oxides or carbon films depending on their location in the circuit.

For the tube gain stage, HagTech has chosen to adapt his low noise Coronet circuit to use in the Chime. This uses a 12AX7 and a 12AU7 (follower) in concert to provide a healthy 30db of gain. The chosen resistors in the signal path are metal oxides.

Jim has also chosen tube rectification for the power supply. The choice was the standard 5Y3 (GZ34) or any one of its many variants. There is a single cap in the B+ power supply circuit. Just in case you were wondering, that cap is a 47uF. Jim also says that you can use the ultra cool 274B. In Jim's own words "274B - actually you probably can.The specified limit for direct capacitive load is when under full output current load. It is mainly a power or peak energy limitation (must limit peak currents). The Chime is not a textbook circuit, you'll note that current is about 1/5th max rating, I also have 220 ohm resistors in series with the anodes, which help to limit peak currents. These resistors not only minimize peak energy dissipation of the rectifier, they also add some series damping to the B+ secondary windings.  A twofer.  As a result, the 47uF may appear too large in value, but in reality it is not."

HagTech has incorporated a couple of nifty features into the Chime. First and as far as I'm concerned the niftiest is the Phase Switch. I know this will be foreign to many, but to get the most out of your recordings you really need one (providing). Not all recordings maintain proper phase. Not all recorded instruments in a given recording are recorded in proper phase (due to phase inversions in the recording process). This phase switch allows you to flip back and forth on the fly and chose the proper setting for each recording that sounds correct to you on your system.

This phenomenon is system and gear dependant. Depending on how many stages and filters each piece of gear you own has, each of those stages will likely invert the signal. There is no way of telling whether your total system inverts the signal or not since there are no standards established within the recording industry regarding phase. To further complicate matters, each instrument has it's own polarity (notice I didn't use phase). Ultimately, it is up to you the listener to decide which position sounds the ‘most correct' to you as you are playing your music.

I first learned of this from unflappable Clark Johnsen. Talking to Clark about this, he suggested that I read his book The Wood Effect and then take the journey myself. After switching the positive and negative leads on my turntables cartridge and playing a few very familiar records, I discovered he was absolutely correct. Recordings that I always thought were veiled and dull sounding came to life. There was now ‘air' and a liveliness to the records I had long since given up on.

Now, to hit you with the 'providing' I mentioned earlier. You must have phase correct speakers in order to hear this. If for any reason your speakers shift phase drastically, you likely won't hear a thing. If you don't hear the newfound openness of old dull recordings, so be it. That just lets you know what piece of gear needs to be upgraded next.

A couple of other features the Chime offers are three selectable inputs. You have two S/PDIF's and a USB interface. The final knob you can twist on the front panel is the volume control. That's right, the Chime comes with a volume attenuator. That means you can drive an amp directly with the chime without the need for a preamp (for those of you of the minimalist persuasion). Kinda cool if I don't say so myself.

My Standard Non-Statement About Sampling Rates

Is I've repeated over and over, I know exactly zip about digital design (get ready, I'm about to plagiarize myself). With the following, I'll try to explain the differing sampling rates as best my feeble mind can comprehend. In the realm of digital to analog conversion, there are hugely differing opinions as to which method of conversion sounds the best. We have non-oversampling and  we have upsampling and we have oversampling as is the case with the HagTech Chime (notice I left out SACD as I'm only speaking of Redbook).

The camps out there will each defend their chosen sampling procedures to the death (if need be). I've found that each of them can sound quite good when done well or quite bad when done poorly. In my case, I've got the AH! Njoe Tjoeb which allows me to use the stock output of the Philips TDA 1545 along with the OPA2604 (or the AD 826) opamp or I can drop in the 24/192 upsampling board if I so desire.

As for my preference in sampling rates, I like them all, but I vacillate. I'll go for a while listening to the stock, NOS chip and then I'll get a wild hair and install the upsampling board and listen to it for a few months. Then I get bored and yank the board back out for something different. As you can tell, I really don't have a preference. I sort of sway with the prevailing winds. I just like the breeze.

When it comes to the sonic differences between the two sampling rates, hopefully I can explain them without causing some sort of flame war or getting too many email bombs. The upsampled units that I've heard tend to exude a large amount of (apparent) detail. I said ‘apparent' because of the mathematic interpolation an upsampler does. The upsampler samples the information on a CD and then ‘approximates' the additional detail through a complicated algorithm. Upsampling (as I understand it) stretches the data points apart (of sorts) and fills in the gaps with approximated data, smoothing the data stream curve. The end result is, the upsampled signal that comes out of your speakers (supposedly) has higher resolution. You hear more detail, there is a greater breathiness to the sound on your CD.

As I stated earlier, done well, upsampling can sound very good. Done poorly, it can sound like cats mating. Upsampling can also bring the soundstage quite a bit more forward into your room. And yes, just ‘average' upsampling can be quite harsh, fatiguing and can have a definite digital sheen to it. In a back to back comparison between the two, non-oversampling can sound a bit dull and lacking in detail. But, after your ears become accustomed to the non-oversampled chip, you begin to understand that the presentation becomes far more relaxed and less aggressive. I hate to use this term but it sounds less forced. In essence, less digital sounding. Even though it isn't vinyl, it contains a few more of its qualities (IMO) than its higher resolution cousin, upsampling. To my ears, oversampling seems to fall somewhere between the two.

I guess what I'm getting at is the differing sampling rates are ultimately a personal preference. Each can sound quite good when done properly. If you want some seriously technical information regarding sampling rates, do a Google search using "upsampling vs. oversampling" as the search parameter. You'll get enough reading material to keep you going for weeks on end.

How Does It Sound

Through the majority of this article, I listened to the Chime behind the Bolder Cable modified Squeeze Box 3 using the S/PDIF interface. The Chime was connected to my DeZorel line filter so that I could get the cleanest power possible. After several hundred hours of break in time, I swapped the stock Electro Harmonix tubes out for a pair of Telefunkin's and a Mullard GZ34 rectifier tube. The tube swap alone was like listening to an entirely different piece of gear.

Of course my reference gear used was my Welborne DRD 300B mono block's driving a pair of Lowther PM2A's in the Medallion cabinets which are actively crossed over at 100Hz to a pair of vintage 15" Goodman subs (circa 1958) driven by the AKSA 55 solid state amp. All of this is connected to my modified Korato KVP 10 dual mono preamp.

Getting right to it, I directly compared the sounds of the Chime to the Mhdt Paradisea and the Bolder Cable modified SB3 analog outputs. Starting at the bottom and working my way up, I found the Chime's bass to fall somewhere between the Mhdt and the Bolder's SB3 outputs. The tightest sounding bass was the Bolder. This wasn't at all surprising considering it was the only solid state output of the lot.

As most of you know, when you introduce tubes to signal path, things like bass tend to sound fuller and bit more rich and flavorful. This was the case with the Chime. The Chimes bass takes on a bit more texture and body. This texture wasn't quite as pronounced as the Mhdt Labs DAC though. The differences between the three though completely audible, were minor in the grand scheme.

The Chime did a great job at reproducing the lower frequencies of everything I threw at it. From YoYo Ma's quarter century old cello, to big heavy bass runs from Victor Wooten, the Chime hung in there with the best of them never embellishing or coming across as too lean. Moving up to the ultra critical midrange I found that the HagTech Chime and its oversampling provided just a hair more detail and resolution than the Paradisea and the Bolder SB3. Again, there was nothing surprising here because of the oversampling scheme Jim has employed in the Chime.

When listening to the Chime, I was very critical to the way it reproduced the midband frequencies. I played literally hundreds of different choices ranging from female vocals to large orchestral pieces to small ensembles. The Chime performed extremely well in all areas. The additional detail provided by the oversampling gave a tad more life to my choices in music. I didn't notice any veiling of the music at all, in fact quite to the contrary. I half expected the MIT output caps to effect the sound more, but they disappeared very well. The instruments like pianos which are extremely sensitive to veiling induced by inferior quality parts or mediocre designs were clean and clear. The Chime let the music come through completely unencumbered.

Finally, moving to the treble region I found the three pretty much on par with each other. Due to the oversampling on the Chime, I did find that there was a bit more detail and resolution that allowed some more refinement and placements of the instruments. The resolving nature of the treble was crisp, clean and well extended on nearly all music. I spent hours on end listening to tunes without any hint of listeners fatigue. That in itself is pretty telling.

When it comes to the audiophile stuff like soundstage and imaging, the Chime did a very nice job at all of these. Since the Chime is oversampled, the soundstage comes forward a fair bit compared to a non-oversampled DAC. The soundstage isn't quite as forward as an upsampled DAC. The soundstage falls somewhere in between the two. To put a dimension to my description, I'd have to say the back of the stage is typically about five feet behind my Lowthers. Considering how forward sounding these speakers are on their own, that's pretty darned good.

Using my usual test for stage width, Pink Floyd's "Signs of Life" from Momentary Lapse of Reason, the lapping water is falling easily three to four feet outside of the speaker cabinets. Again, this is well on par with the best the DAC's I've listened to. Moving on to instrument placement, I've chosen the Adam Rafferty Trio release Three Souls. This is one of those great pieces of music that happens to be of pure audiophile quality. On the cut "Hurricane Bertha" it sounds as if the recording engineer has chosen  a simple stereo mic setup above the drums. This gives us the illusion of the actual drum placement when we listen. With the Chime, the placement of the drums across the virtual soundstage is very good. When you close your eyes and listen, you can easily hear the physical separation of the individual drums within the kit. Overall, I found the HagTech Chime to be an outstanding performer in every aspect.

S/PDIF vs. USB

Leading up to the Bolder Modified Sqeezebox review and this article, I had some very strong opinions about computer based audio. EAC, FLAC and the modified Squeezebox proved my preconceived opinions about computer based audio completely wrong. Even as late as a year or so ago, one or two of the local guys had brought by there iPods and wanted to plug them into my system. I always resisted because of my prejudice of most things digital. I thought their iPod's would sound even worse than a standard CD (which already sounds pretty ill unless you've got an extremely expensive CD player).

Knowing just how good the Bolder Cable modified Squeezebox is, I decided to take the next step and try the Chime's USB interface to see if I'd get proved wrong one more time. As I read and as I think about it logically, the way I've set my computer and the Chime USB DAC up isn't exactly optimal. Since the Chime sits about ten feet from me and my Gateway Laptop is... well... on my lap, I didn't have loads of choices when it came to short USB cables. I realize that when it comes to cables and interconnects the audiophile absolute is ‘the shorter, the better'. Unfortunately, this wasn't going to happen. I wish I had room on my stand for a laptop and a big fat 2' cord but it wasn't to be. So instead I carefully routed my 12 foot USB cable carefully so I didn't get any RFI from any power cords or power supplies. It worked just fine.

Before I start talking about how the USB interface sounds, you need to know that you now need a decent FLAC or WAV (or OGG or any other format you wish) player to interface with the Chime. Since I use FLAC encoding there are two that I considered and played with. The first is Soft Squeeze, the little Javascript player that comes free with the Slim Server software. The next is Foobar 2000, some more Freeware. There are a number of other FLAC players and plug ins for various programs like Winamp, Windows Media Player and Nero available. This go around I won't be discussing the differences between all of them but know that FLAC is well supported out there on the Web.

After recognizing my ripped music folders by both programs, I compared them side by side, real time by level matching and toggling play and pause on the a few different Eric Clapton and BB King songs. Both Foobar and Squeezesoft sounded quite good but in the end I settled on Foobar 2000. It gave me a bit more flexibility on setting parameters (caching, bit rates and the like). Foobar isn't the most intuitive program in the world but after playing with it for a while and searching under each and every menu and clicking buttons just to see what happens, you finally get the hang of it. Oh, the other thing you need to know is that when you use this setup, both Foobar and Soft Squeeze now use your Windows (or Mac I would assume) internal speaker controls to adjust the output volume. In other words, you use the WAVE balance and volume properties internal to Windows to set volume levels.

OK, so much for the setup, on to the listening. Flipping actively back and forth from the USB and the Squeezebox there are some differences. To be completely honest, they are pretty minimal. The first thing I listened for was clarity. Here we have such a minimal difference, I'm not sure it's worthy of mentioning. Sure there are things contributing to the differences such as the power supply used with the Bolder Modified SB not to mention the digital mods themselves. Oh, and lets not forget my solid silver digital cable. It's going to affect the sound too.

For the next few tests, I used the most sibilant CD (now FLAC) that I own, Eva Cassidy's Songbird. I chose the track Autumn Leaves and played it at levels that which mirrored jets taking off. This track played on the Lowthers is shear torture if the upstream electronics are not up to the task. On the other hand, if the electronics are extremely good, her voice can send chills to every part of my body.

When it comes to background noise, both seemed pretty much equally quiet though on occasion Foobar acted up and gave me some nasty processing noise. I feel most of that is due to Foobar itself and the way it uses the system resources but who knows, maybe it's my Gateway and its architecture. This is the critical issue in my eyes, sibilance resulting from jitter. In this comparison the S/PDIF sounded better or should I use the term smoother. Here there really isn't a huge difference. I do notice a bit more bite in the hard S's and Ch's as Eva sings but it truly is minimal in my opinion. When it comes to the soundstage, the USB connection seems just a tad more forward than the modified SB fed into S/PDIF of the Chime. The placement of the instruments and focus hang together pretty well. I honestly can't say that things shifted much (if at all) when I switched between the USB interface and the S/PDIF.

When it comes to the bass treble and midrange reproduction differences, again the two were fairly minimal. There was nothing notable in the treble and upper midrange regions. When it came to the bass and midbass using the USB interface, the bass was just a tad softer and didn't carry quite as much weight as the S/PDIF. I honestly think that is attributable to the 12' USB cord that I am using rather than the USB interface of the Chime. I can't be sure but from what I've read from the guys that are deeper into this than me, that is one of the noticeable differences by changing to a better, shorter USB cable.

The bottom line, although in my system the S/PDIF connection sounded better, listening using the USB was very nearly as good. I think with a few tweaks like a better and shorter USB cable, I wouldn't be able to hear a discernable difference. Well, I guess even an old dog can learn a few new tricks after all.

Complaints

As some of you know, the Lowthers are a brutally revealing speaker, especially when mated with poor quality electronics upstream. The PM2A's will absolutely show every wart and blemish if one exists. It's like using a magnifying glass for audio gear. The only thing that I heard during my time with the Chime was the very occasional grit and glare of certain music (read = rock) at very high SPL's (read = over 100dB) that I'm not getting with a NOS DAC. This could be due to the choice of the stock parts used in the Chime or it could be the recording quality or it could be that my NOS DAC isn't as revealing as the Chime. When it comes to the Chime, Jim uses off the shelf parts from Digikey to do this build (with the notable exception of the MIT coupling caps).

Please, don't misread what I just typed. What I referred to was only with Rock music played extremely loud on Lowthers. Unless you know intimately the way Lowthers sound, they can not be compared to traditional speakers on any level. There is a very strong chance you'll never hear what I mentioned as your speakers don't sound anything like these single drivers. Having explored the sound of cottage industry parts in different positions within many audio circuits I suspect what I am hearing at very high SPL's is attributable with the choice of these standard resistors and capacitors in the design. These parts can be easily substituted for a cottage industry pieces at a relatively minimal cost. Granted, you can easily go overboard using Tantalum resistors and Teflon caps but better sounding parts can be had fairly reasonably on the web.

The fact of the matter is, I'll be doing a follow up to this article sometime later this year where I'll be taking my own advice and overbuilding the Chime. I plan on spending way too much on those cottage industry parts in order to squeeze every last drop of life out of the Chime.

Conclusion

Needless to say, I'm wholly impressed with the sound of the Hagerman Technology Chime. Overall it has a very neutral approach to the music (in tube terms). The tubed output stage doesn't add any of the euphonic silliness that you read so much about. The output signal is extremely clean and detailed. The increased dynamics and wide open sound of the tubed output stage are all that you would expect from a good design. The treble is clean and the bass is nice and tight. The Chime provides a tad more detail than a really good non-oversampling DAC like the Mhdt Labs though not quite as much as an upsampled DAC.

At about $950 in kit form or $1799 fully assembled, the Chime represents a very good value. So, again it all comes down to your listening preferences. Have you tried non-oversampling DAC's and want a bit more detail? Have you also tried upsampling DAC's and found that they are too forward sounding for your tastes? If so, the Hagerman Technologies Chime might be exactly what you've been looking for. It's presentation falls directly in between the non-oversampling and upsampled DAC (speaking in terms of detail).

If you are looking to build your own DAC, this is one of the very few tubed DAC kits that you will find on the market. Though I haven't built mine yet, I've read through the instruction booklet and looked at the PC boards. It seems to be a fairly simple build. If you don't feel like doing the DIY thing, you can always have Jim assemble it for you. Even at the assembled price, the Chime still represents a very good deal. If you are in the market for a new DAC, the HagTech Chime is well worth considering.

My Ratings

Please keep in mind this rating system is used to compare the Hagerman Technology Chime DAC against absolute perfection, or a money no object DAC design. If you see what you think may be a low(ish) score, it's because there are DAC designs that are even more refined but consequently cost considerably more. To top that off, if I assign 5's across the board, I've just painted myself into a corner leaving no room for that ‘ultimate' DAC. You won't see me handing out many 5's. In turn, I feel I need to leave room in the ratings system to accommodate those DAC's.

Specifications

Type: Tubed ditial to analog converter with USB and SPDIF input

Tube Compliment: 12AX7, 12AU7, 5Y3GT (or GZ34)

Input Impedance: 75 ohm (S/PDIF)

Inputs: two S/PDIF and USB

Frequency Response: 10Hz to 100kHz

Distortion (analog) - 0.03% @1kHz @1Vrms

Output Impedance: 1k ohm

Output Voltage - 1.2Vrms full scale

Signal To Noise: 92dB (A-weighted)

Dimensions: 7.25 x 11.65 (PCB, W x H in inches)
                       8 x 12 x 3 (chassis, W x H in inches)

Weight: 9.5 lbs.

Input Voltage: 100V, 110V, 120V, 200V, 220V, 240V

Price: Assembled = $1799
           Half-Kit approximately $99 (pcb) + $499 (hagdac) + approx $140 (electronics) + approx $70 (iron) + approx $30 (tubes) + $85 (chassis)

Company Information

Hagerman Technology LLC
P.O. Box 26437
Honolulu, HI 96825

Voice: (808) 383-2704
Fax: (808) 394-6076
E-mail - jim@hagtech.com
Website: www.hagtech.com