> The max in-out differential voltage to the LM317 is 40V so I'd
> want to drop a few volts off the supply, at least 5V
>
> 2N3055 gain is 20-70 @ 4A, transformer rated at 34V 6.5A
>
> Vee will be a small -ve voltage so the output can go down to 0V
>
> So, if I aimed for a Vout max of 38V (assuming regulator/transistor/
> resistor losses will probably not quite reach that), at 6.5A that implies
> a worst case base current of about 320mA, which will come from the
> LM317/350, and will pass through the zener

The LM317 doesn't need to be ground referenced, and there are 60V
versions available from mouser (512-LM317AHVT).

You could also use two LM317s in a "tracking pre-regulator" found in
the app notes of the LM317 from TI:

http://focus.ti.com/lit/ds/symlink/lm317.pdf

Information on floating the LM317 is available, in this mode you can
regulate from Vin to (Vin-LM317) :

http://www.national.com/ms/LB/LB-47.pdf

I would try to combine any of these with a pass transistor rather than
using a zener to protect the LM317.
--=20
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