CanJam at RMAF 2012: The Sennheiser HDVA 600 Balanced Headphone Amplifier
Sennheiser HDVA 600 ($1599) and HDVD 800 ($1999)
It's been over a decade since I helped develop the world's first balanced headphone amplifier, the HeadRoom BlockHead (Stereophile review here). At the time, it was as much a PR stunt as a serious effort to get even better sound from headphones. Turns out, balanced headphone amplification is a pretty good thing, and many small enthusiast companies have followed suit. To the best of my knowledge, however, none of the larger companies have produced a balanced headphone amp...that is until now. I can't tell you how cool it is for me to see balanced connectors on the front of Sennheiser's new amps.
One of the important things to know about balanced headphone amps is that the right way to build one is to have four separate and matched amplifier channels in the amp. Two each for the left and right channels, one amplifying the normal signal, and one amplifying the inverted signal. Beware of headphone amps in which the signal is single-ended somewhere in the circuit.
It appears that Sennheiser gets this, and their press release includes this information:
Signal processing in the hi-fi devices is fully symmetrical. That means that not only the signal input into the amplifier is symmetrical but also the signal output and therefore the connection to the headphones. “The fully symmetrical principle effectively compensates for interference and distortion. The sound therefore becomes much clearer as total harmonic distortion is minimized," explained Axel Grell, Sennheiser’s high-end product manager at Sennheiser. However, the headphones can also be connected using a normal 6.3 mm jack plug. The amplifiers are also equipped with an asymmetrical input socket; when using this input, the incoming signals are symmetrized before further processing takes place.