From what I have seen the people that are playing with "balanced" headphone output (which seems to be more concerned with supplying separate signal cold rails for each channel rather than balancing the output signal with respect to ground) are using a full sized 3 pin XLR connector for each channel. So that is what we are using. Not sure that I grasp the second question properly, but the single ended and balanced outputs are all switched from the output transformer, so there won't be a need for any additional transformers.
From what I understand......
16 ohms 1.8 volts 112mA
32 ohms 2.5 volts 80mA
64 ohms 3.6 volts 56mA
128 ohms 5.0 volts 40mA
Want to give a status update to those who have pre-ordered. We haven't forgotten about you! As happens sometimes the process of getting the parts together is taking a little longer than expected. Our laser cutter has been swamped and it took a while for him to get us a quote so we could order the chassis plates. They are now in the production queue as are the transformers. Should be a couple/three weeks and we will have some kits to ship.
We just did the test firing of a new headphone amp prototype that I plan to take to the Bay Area Head Fi meet this weekend. The amp is designed as a complement to the Crack OTL headphone amp for high impedance headphones. This new design is a WOT (With Output Transformer) design that has been developed for low impedance headphones. I decided to call it Smack. It uses two 5687 tubes. One half of each 5687 is an active loaded single gain stage that is parafeed coupled to an output transformer. The prototype has a single tap of 32 ohms, however we might alter the production transformer design so that it could be configured for 32, 64 and 128 ohms. The second half of each 5687 is used in an active loaded hybrid shunt regulator. The prototype has been built on a S.E.X. amp chassis and uses the same PT-3 power transformer used in Crack, S.E.X. and Foreplay III. The gain stage and shunt reg use the new Soft Start PC board that we use in the new Paramount.
Unfortunately I only have some inexpensive Sennheiser 201s here today to try the amp with. But even with those it's showing promise. It's dead quiet, seems pretty quick and there seems to be pretty good bass for an amp that's about 2 minutes old. Gonna burn it in a bit and we'll see what folks think at the meet. Before anyone asks, I don't have a firm price. But it would probably hit somewhere in the $350-$400 range.