I have a tube preamplifier and I would like to add a HP out in it which is in par with the rest. Space is quite limited so I can not build an additional tube stage with output transformer. I am looking for some simple yet good quality solid-state circuit for my headphones (2x30 ohms). I think I need a gain between 2x and 5x. I have +12V available. Can I use an integrated buffer, like the BUF03 () which I believe is out of production) or the new AD815? Any ideas welcome.