Hi, I'm about to start building my own LM3886 gainclone, only a few parts are yet to arrive.
I'll use two 19.4v 6.2A transformers, and two LT1084 or LT1584 for regulation.
Sources will be mainly computer and phone and my doubt is if I'll need any kind of preamp/buffer and how to implement volume adjustment, I've ordered a few OPA827, BUF634 and OPA2134PA just in case.
Any thoughts are welcome.

 

A computer should be able to deliver audio in the range of a whole volt, so a pre-amp seems not necessary to me. A volume control is so easy. Just buy an audio taper pot in the range of 10k to 100k. What's the problem?

 

The standard "audio out" connections these days from PC or 'phone will be the headphone out socket. That should be good for at least a couple of volts.

You won't need a preamp on a gainclone if you are driving it from a headphone out socket.

It's interesting to see you are going for dual power rail voltage regulation on your gainclone. I did it that way too, before it became trendy to have regulated PSU rails;
http://www.romanblack.com/gainamp.htm