The Tripath based TK2050 amplifier by Hifimediy has been gaining quite a following at diyaudio.com. From what I’ve gathered around the internet, Tripath went bankrupt in 2007, but apparently some Tripath chips are still available, and there is also a possibility of some other companies (probably China) who’ll continue to produce these chips. Here is a short introduction on Tripath from Wikipedia:
A Class T amplifier is an audio amplifier IC design. Rather than being a separate “class” of amplifier, Class T is a registered trademark for Tripath’s amplifier technologies.
It is an implementation of Class D amplifiers, but improves the control scheme to create more efficient and higher quality audio amplification. One of the amplifiers, the TA2020, was named one of the twenty-five chips that ‘shook the world” by the IEEE Spectrum magazine.
The control signals in Class T amplifiers may be computed using digital signal processing or fully analog techniques. Currently available implementations use a loop similar to a higher order Delta-Sigma (ΔΣ) (or sigma-delta) modulator, with an internal digital clock to control the sampled comparator. The two key aspects of this topology are that (1), feedback is taken directly from the switching node rather than the filtered output, and (2), the higher order loop provides much higher loop gain at high audio frequencies than would be possible in a conventional single pole amplifier.
Despite increased performance at a price similar to class D technology, financial difficulties have caused Tripath to file for Chapter 11 bankruptcy protection on 8 February 2007.
You can read more about the amplifier at the Hifimediy’s product page, as they do a fairly thorough explanation of the product page. But for now, we’re interested in how the TK2050 performs, especially with headphones.
David brought the TK2050 to my place with the sole intention of trying it with the Hifiman HE-6, which is notoriously hard to drive. Of course, I’ve found that the production version of the HE-6 didn’t quite need a speaker amplifier, as it ran well on many headphone amplifiers such as the M-Stage and the Hifiman EF-5. But we always wanted to try out new things and find better alternatives, hence the TK2050. Previously, the only other speaker amplifier I’ve used with the HE-6 is the Nelson Pass designed Adcom GFA5802, which is a 300W power amplifier I use to drive my Apogee Slant 8 speakers. It sounds quite sweet, other than the high noise level due to the 300W power rating. But such a set up is definitely not very power efficient, and I don’t feel comfortable hooking up a headphone to a 300W power amplifier.
The TK2050 board comes fully assembled from Hifimediy. It’s not quite ready to use yet, as you need to hook up an input connector and set up the power supply. Without much delay, I soldered some input cables with RCA terminals at the end. The output signal is delivered through the screw on connectors mounted on the PCB. The power supply we use is a Meanwell S-350, which is the recommended power supply for the TK2050. We adjusted the power supply for a 30V output. There are also two trimpots near to the potentiometer to adjust DC-Offset. We adjusted it to very close to 0 mV. Now, the important thing about the TK2050 is that you can’t short the output ground, meaning you have to reterminate your headphones with XLRs. Luckily, the HE-6 comes with balanced cables, and previously I’ve fabricated an XLR to bare wire adapter for use with speaker amplifiers. Additionally, I also have a balanced cable for the HD650 and the HD800, so we can use those headphones with the 100W Tripath as well.
The 100W (at 4 Ohms) Tripath conveniently drives the HE-6 at around 11-12 O’clock on the volume knob. After all, the TK2050 is a speaker amplifier and should have little problems driving any headphones, no matter how inefficient, to ear-shattering loudness levels. The question then becomes, how does it sound? My previous experience of using speaker amps to drive the HE-6 was with the 300W Adcom, and one of the main issue with it is that its high noise level are quite audible when driving headphones. The TK2050, on the other hand is very clean sounding and zero noise. Instantly I notice that the sound is sweet and enjoyable. Some people say that class D amplifiers are harsh and cold sounding, but the TK2050 is none of those. There is no harshness, and the sound is far from cold. I also notice that the midrange is very special on the TK2050. There is a slight midrange boost, resulting in a slightly mid-centric sound, but it’s not extremely so. What’s more, it’s one of the sweetest sounding midrange I’ve heard from a non vacuum-tube amp. The synergy with the HE-6 is quite wonderful and it’s been the main amp that I use to drive the HE-6 with for the past few days since I’ve received it.
All that power definitely has some merits, and the TK2050 feels so effortless in driving the HE-6 Orthodynamic, and likewise the Sennheiser HD650, which I’ve only experience driven so effortlessly on the Beta22. I’ve always felt that the EF-5 had sufficient power to drive the HE-6, but now that I’ve listened to it on the Tripath, I went back and felt that the EF-5 didn’t have the same effortlessness that I’m hearing out of the Tripath. The EF-5 also sounds less clean when compared to the Class-D TK2050. Driving the HD650, the sound feels just as effortless while the bass area no longer clumped together, and the HD650 truly sounds alive on this set up. This is amazing, of course, because it took me nothing short of the Beta22 to hear the HD650 sounds so alive.
Of course the next question that I wanted to answer is, how close to the $2,000 balanced Beta22 can this $100 TK2050 get? Previously the Beta22 was the main amp that I use to drive the HD650 and the HE-6. Comparing the two, I can immediately notice the superior detail levels, soundstage, and frequency extension of the Beta22. So, perhaps I was being a little too enthusiastic over the TK2050. And yet, though the TK2050 falls short of the Beta22′s technicalities, its sound signature is definitely sweeter than the Beta22, especially with the sweet midrange that is bound to get a lot of people hooked. The TK2050 is not a slouch in technicalities, but it just can’t be compared to the Beta22. However, at a certain point there is just enough technicalities to please most music listeners, and the TK2050 has passed through that point. I actually wonder if it can be improved further by using a better power supply like the Sigma22, but the whole point of the TK2050 is how it is such a great sounding amplifier for less than $100. Perhaps the only catch to it being that it doesn’t come in a ready to use package. At the very least you would need to solder in the input connectors, set the voltage output on the power supply, and adjust the DC offset. All of this requires a small degree of DIY skills, but definitely much easier than say building a Cmoy.
I’ve only spent a few days with the amplifier, so I apologize about the lack of depth in the article. I truly feel that the TK2050 is a special amp, and I just want to get the word out there. However, feel free to ask any questions you may have in the comments section, and I’ll try to answer it since the amplifier will stay at my place for a little while.
The TK2050 amplifier sells for $38, and the Meanwell PSU for $41, both from Hifimediy.com.