X-BOSOZ/SOZ-Lite

[needtubes]

Hi all-

I have been putting a lot of thought into all the Pass variations for use as a headphone amp. I don't want to use a high voltage, and would prefer to keep it under +/-24V. I also don't really want to have to build the CCS and provide extreme large amounts of heatsinking (not as huge an issue considering headphone use). I also don't want any electrolytic caps in the signal path, so that more or less eliminates the original Zen, Zen revisited, and other Zen variations, leaving me with just the SOZ and BOSOZ. Of course, the amp is very inefficient, and the current source resistors would be very warm. So, as was done with the Zen Lite, I though about doing a SOZ-Lite. But, the amp is for headphones... so a single SOZ gain stage won't really do. Since I am using 300-ohm Sennheiser HD580s, I need a decent amount of voltage gain. So, I figured using the BOSOZ with different resistor values to accomodate the lower voltage would be ok for a gain stage, then have that driving the modified low-power X-SOZ-Lite balanced output to eliminate need for electrolytic coupling caps (I would only have film caps on inputs and between gain stages... more tolerable than electrolytics). Attached is my idea of how this could work. Comments are welcome and appreciated. Thanks!

[Henrik]

Hi needtubes
I have been playing around with this X-circiut in the sim. I am planning a version for speakers, but it might be nice for a headphone amp too.
With 2V ampl input you get 14V ampl out, that shoud be enough.
It dissipates 15W total, it could propably be adjustet to less.
Just a suggestion, and the scenatic may need some tuning, it's more for an example of a kind. The CCS BJT´s need some base resistors, they have to be calculated so they match the base emitter current.
Remember you need to rewire your headphone, since you need to connect through 4 wires total.
Best regards Henrik.