Albireo β Cygni portable balanced headphone amplifier and Hirose HR10A connector
More information about the Albireo balanced amp project can be found here [Japanese]
I had the chance to hear this amp in December via a nice pair of Ultrasone ED 8 headphones. Okay, so I've not heard the headphones in a long time, so that sort of put me at a disadvantage, but there certainly is a goodly amount of power beneath this amp. It uses 4 LR6 AA sized batteries for what I think is 6 volts of power split and up to 20 hours of battery life. Unfortunately, it shouldn't be used with balanced armature earphones.
Finally, it costs nearly 700$, so obviously isn't for the ... faint of wallet. It is a 100% enthusiast product for those who want to go balanced with their full-size headphones.
It isn't production ready, at least in vast quantities, but it and its cousins (which I've heard since then) from a number of ingenuous DIY Japanese audiophiles share a number of great bits: they feed headphones not from dual mini TRS outputs, but from a proprietary (and here's the best part) current production Hirose connector.
The Hirose HR10A IS proprietary, yes, but it is also strong, latching its male/female parts together with a twist. An internal spring allows the external circumference ring to loosen or tighten its grip in what is the most ingenious use of connection tech I've seen in portable audio.
Its schematic is this:
A number of Japanese manufacturers/enthusiasts are using this connector because it is both strong and light. Currently, the only production balanced amp: RSA Protector uses a now defunct proprietary 4-pin connector which can only be special ordered and is now only available in very small quantities in certain old-stock parts dealers. EDIT: I've news that the RSA connector is available but in very small quantities unless special ordered.
Both the Protector and the Albireo aren't fully balanced amps; each split a single ended signal between channels and apply phase split to 'balance' the sound. The effect is pretty good. But the part which spits the signal to headphones, that is a war which has just begun. Sadly, RSA didn't check the worldwide market before making their amp meaning that their head-start on the market may force a lop-sided run for the RSA out-of-production part. When it dries up, even RSA will be forced to use a different connector. Imagine having to plug a different connector into each phone/DAP you have.
E.G., the iPod uses a square connector and your home stereo a round one; chaos would ensue and maybe it has.
At least Albireo and the manufacturers looking at the Hirose HR10A are looking at a strong, easy-to-wire and current production model for connection.
Again, more information about purchasing the Albireo balanced amp project can be found here [Japanese]
Here are some more photos of the Albireo: