Japanese company TEAC has been around since the 50's, and is still around
today. The
HA-501 headphone amplifier was released in 2012 as part of their '500' series of mid-size (29 cm width) stereo components aimed at a modern, computer-centric audio lifestyle. Although other products in the range are still active, the HA-501 is now sadly discontinued.
TEAC (the company also makes products under the TASCAM and ESOTERIC brands) seems to have succeeded where other Japanese audio makers like Onkyo, Kenwood, Pioneer, and JVC failed. I like to think it's because they adapted to the trends (portable audio, network audio, headphone listening, streaming, computer audio) without abandoning their core values of quality and aesthetics. It's a tightly focused product lineup, and a very attractive one in both feature set and appearance. Their new
UD-701N (part of the larger 700 series) is a real tour-de-force: high-quality amp, headphone amp, preamp, DAC, and wireless network receiver all in one nicely designed package.
The HA-501, on the other hand, always felt like a bit of a throwback even on release. All analog, the entire chassis was devoted to just driving a single pair of headphones (though it does pinch hit as a simple line preamp). Considering TEAC offered headphone outs on all the other 500 series components such as the DACs and integrateds, it's understandable that most consumers would fail to see the merit of doubling their investment to get a feature they already had. Today, while the UD-501 and UD-301 DAC/headphone amps are still high quite highly sought after in the Japanese market, the HA-501 sees much less interest, typically selling used for just $200-250 USD. As such, it's a bit of a sleeper deal, if you have the source and the headphones lined up to make the most of it.
The dual-mono circuits of the HA-501 are based on a single op-amp in each channel (MUSES8920) fronting a class-A transistor output buffer. From the high-ish distortion
measurements I suspect the output is running open loop. As well as being able to switch the line outs from pass-through to preamp mode, the headphone amp has the unusual feature of a damping level control, which, again from the
audioscience testing, seems to simply switch 0-5 ohms into the output path rather than adjust the feedback level. Some headphones might benefit from the extra isolation, others likely won't, but it's a nice little tweak to have.* It also has balanced inputs. The nice big chunky toroidal power transformer is great to see (the chassis weighs in at a hefty 4.1 kg), though I do worry a little that the +15 V and -15 V are established with LM7815/7915 regulators instead of something nicer. I'll establish the truth when I have mine in hand. Although the HA-501 never seems to gain much popularity even within the hifi community the few reviews that I have found have been uniformly positive. Although I don't expect it to conquer my current reference, the
Sapphire IV, I do expect it to play in the same league and have a similar sonic signature, though perhaps a few notches warmer and looser.
I am looking forward to its arrival, to say the least.
*
I have to comment on this. Adding a damping factor control on a consumer-facing product like this is just a crazy idea, because 99% of the potential market either has no idea what it is or does, or had an incorrect understanding of what it is or does. It's that "damn the torpedoes!" attitude that attracted me. I can just imagine the meeting at TEAC between the headstrong designer (I'm imagining an old engineer guy, way past normal retirement, revered at the company) and the younger marketing team, because, yeah, the designer clearly won that battle!