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Bias adjustment for a digital amp?
Unscrew four screws and remove the top. There are two mini potentiometers for adjusting output bias and to obtain optimum sound while minimizing the power-on transients which are inherent in the Tripath chip or rather, most Class-D amps such as NuForce. According to Ricky Leung, Trends Audio's chief designer, adjusting bias is important for Tripath amps. "Since the Tripath TA2024 is a single-ended amplifier, both speaker terminals (+ve and -ve) of each channel should actually have positive DC voltage (~ +6.0Vdc) relative to the GND. Then they are bridged to provide the output signal to the speakers (+ve and -ve is zero DC voltage in theory). According to the TA2024 specs, the IC itself allows the +ve and -ve terminals to have up to +/- 150mV bias in between. Too high a DC bias voltage will increase the background noise, reduce the actual signal-to-noise ratio and degrade the sound performance. And, it may also be harmful to speakers, reducing their life expectancy, especially for low impedance speakers. So it is advisable to check every now and then to offset the DC bias voltage between the +ve & -ve terminals of each channel to (or close to) zero."


The amps were factory-set prior to shipping but we know how rough a journey that could be. In addition to the review amp I received, I ordered some more as Christmas gifts for friends and saved some spares for myself to experiment with multi channel. I checked all the amps upon arrival and found that most bias settings were within a +/– 2mV range. The worst case was just above 8mV, still well within the Tripath chip tolerance. During my two months with four TA-10s, I checked the bias after approximately every 20 hours of play and found the fluctuation to be within 2.0mV. That's very stable. For accuracy, it's good to run the amp for at least 5 minutes before you take the reading. You do not need the amp to be loaded (connected to speakers) to take the reading. The trimmer close to the front panel controls the right channel.


Trained to jump obstacles
Now the most interesting part: on the PCB right next to the volume pot, there are eight pins and four jumpers for you to juggle around in case you want to bypass the volume control and turn the amp into a power amp. Isn't that clever? For the DIYers, you'll also notice that on the PCB there are nearly exclusively through-hole components for you to modify to your heart's content. (Well, except for the TA-2024 chip and four SMD diodes for preventing overshoot of the output signals. More on modifications later.)


Trends Audio also provides customers with an AC/DC adaptor which automatically accepts 100-240V AC (50/60Hz) and outputs 12V DC (3 amps). The IEC main power receptacle allow you to choose your own power cable if you don't fancy the standard cable that comes with the bundle. (But I wonder how many people would bother.) Performance wise, the TA-10 yields 15/10 watts x 2 (4/8 ohms) with a S/N ratio of 98dB and THD measuring 0.1% at 11/6 watts of output (4/8 ohms). That's not bad by tube amp standards and adequately qualifies for 'audiophile' grade sound quality. Price wise, the TA-10 would throw the rest of most any system out of balance, even for an average hobbyist. Understandably, this is not your everyday kind of amp. My task therefore was to find out (1) how humble one could go with a well-matched setup without degrading the overall sonic quality and (2), how extravagant but still within reason one could push the other way, particularly with introducing a preamp and what the associated sonic gains would be.


The dB and CD jigsaw puzzle
Judging from the amp's small output power and small power supply, the choice of loudspeakers seems limited. But is that so? To get my bearings on the whole thing, I started with common sense, which I believe should be a pair of high-efficiency speakers. I first set up the TA-10 with the 94dB/8 ohm Loth-X BS-1 (the same speakers that 6moons reader David Dye used with his Sonic Impact T-amp) and the Restek Radiant CD player as source. Although I'd been warned by Jeff's article that these T-amps could be flabbergasting, I was still flabbergasted. By its effortless and relaxed layering and soundstage reproduction abilities. By its purity and transparency of sound. Above all, by its priceless presentation of music. If you blindfolded me and told me that this amp cost $1,000, I'd dare not dispute you. In fact, I don't care. For this kind of money, to get this kind of music reproduction, I feel contented and thankful straight from the bottom of my heart. I care not whatever audiophile sonic attributes you throw at me. I just enjoy my music, thank you very much!


Earlier on when writing my preview, I also tried the TA-10 with the 89dB/8-ohm JMlab Micron and I thought it sounded just as good. On closer hearing, I found the Micron a little too mechanical, in other words too much hifi and not enough music. Permission to speak freely in HiFi dialect since that's my job here: The bass tended to roll off too early at the lowest octave, making the mid-low transition thin. I'd blame the speakers and not the amp because when I replaced the Micron with a pair of really LoFi Quest QT-66s, to my surprise musicality reigned once more. The Quest QT-66 is an 89dB /8-ohm floorstanding mini tower with two 6.5" woofers and one 1" dome tweeter in a d'Appolito array. On sale a few years back for C$200/pr, these speakers managed to punch out credible bass (claimed to 40Hz) and wove coherent mid and high octaves that brought out the best (or masked the worst) of digital amps. By the way, I also downgraded the source equipment from the Restek to a 1994 NEC Multispin CDR-401G external CD-ROM reader that boasted Play/Stop/Next/Previous push buttons and an LCD track display on the front, coaxial digital out on the back and headphone jack on the side.

Other than not having a remote control, this C$50 (shipping included) eBay item actually made a very competent top-loading CD player, probably the best in that price category. What I heard was perhaps a little direct and blatant -- not enough suavity and grace -- but it didn't rob me of music enjoyment. Vocals were arguably a little harsh and spicy but pianos were strikingly forceful, especially when I split up the output signals from the headphone jack with a Y-adapter and fed one pair of headphone-to-RCA cables to the paired Quest QS8II powered subwoofers. You'd probably notice from the photograph that the listening room was actually more of a TV room and therefore far from ideal. The speakers were spaced 10 feet apart, with a 46" DLP back-projection TV and two almost equally big cabinets in between. Yet, the TA-10 and the Quest had enough music to fill up the entire gap in the middle, voiding the void, projecting a soundstage right through and beyond the three bulky eye-soars and mental blocks as if they did not exist. When Alexandre Tharaud's inspired reading
of Ravel's Mirrors [Harmonia Mundi HMC 901811.12] was played, the Steinway was there, literally 6 feet behind the TV.


What about the pungency in the tone? Yes, the NEC is designed to read computer data at 3 x speed and the Quest is built for home theater. The sound they produce might be by audiophile standard a little too fast, too grainy and could be interpreted as stressed. But I'd have that taken care of in no time. Another eBay item that I bought recently was the Deltec Little Bit DAC. I used to have this wonderful little gem but traded up for the flagship model PDM-Two many years ago. Also based on the Philips 7350 bit-stream chip, this DAC makes music in the most effortless, spontaneous way. When I saw it on eBay selling for $120, I lost no time in making an offer. What it's really good at is taking out all the pointed edges and providing the perfect buffer between the NEC and the Quest speakers. Everything became suave and graceful. What we've got here for a total budget of $500 (not counting the cables and subs) is a musical system that allows you to get close to the heart of music.


At this stage, I was still unable to assimilate the unrestrained, warm silky sound of the Restek/TA-10/Loth-X synergy. I think the 'crossoverless' high-efficient Loth-X had a crucial role to play, which made me believe that finding the matching speakers the for TA-10 is more than half the battle. The Loth-X BS-1 is a bass-reflex design with a 6" Lowther full-range driver and a 1" dome tweeter with a single capacitor in lieu of a more complex crossover. Compared to the full-range single driver back-loaded horn or transmission line models I've heard, I prefer the clarity and well-proportioned soundstage of the BS-1. Stacking two of them in a D'Appolito array can achieve the same grandeur and sound level impact of their big brothers without the muffled nasal sound. Too bad the Singaporean manufacturer has decided to stop production last year. The Toronto dealer Song Audio here still had a few pairs in stock when I was writing this review.


Another good match within the same price bracket would be the Canadian Unity Audio Inner Spirit or the American Omega Super 3, both using a 4.5" full-range Fostex. I recently received a pair of Inner Spirit in beautiful Serene White hand-finished multi-coated enamel for review. These rear-ported mini monitor sized speakers (8.25" x 8.25" x 12.75") have a soundstage bigger and deeper than what seems to be implied by their looks. Although the lowest octave seems to be slightly less expressive than the Loth-X BS-1, which is equipped with a bigger driver and dives a few cycles deeper (55Hz vs. 59, the mids and treble are amazingly coherent. Imaging is equally if not more well-defined, fully capturing the strengths of the Trends amp. I'll be giving a full report on this excellent value 92dB efficient speaker in an upcoming review.


Can one be more ambitious in speaker choices? The TA-10 was small and portable enough to go hunting. The first pair of speakers I tried was a line array prototype built by George Tordai of Audio Zone. Towering over 6 feet, twenty 4" full-range drivers in parallel comfortably yield an efficiency of no less than 110dB. The real potency of these speakers was somehow handicapped by the small listening room and, according to George, the lack of an equalizer to fine tune the bass. Judging from the wrap-around concert hall ambience which I experienced that day however, capable and adventurous DIYers should consider pursuing that avenue.