There are lots of great old ~800V transformers floating around on eBay that you can buy for a song. Many of them have a current rating that is too low for our general needs, 80-100mA range. Not having the right kind of background and experience, I'm having some difficulty understanding what application these PT's were intended for. If you can tame an 800V secondary to 300-350VDC and squeeze out 100-120mA, you've got what you need for many lower power PP guitar amplifiers. The remaining challenge is finding a choke with an adequate mA rating that won't break the bank. I've gathered anything from about 4H to 20H will do the job.
From time to time I troll eBay for old iron, but I rarely buy anything because my general rule, a price limit of about $20 (+/- depending on exactly what), including shipping. I figure I won't get hurt for $20 if I get a dud, which happens every now and then, like that nice $10 choke I bought that turned out to be 15H 20mA, not 200mA, LOL. OTOH, one time I scored a Stancor 4H 250mA that I'm saving for something I build with 6L6 or EL34 tubes. In any case, there are several appropriate Hammond chokes in the < $30 range, so this isn't something that will break the piggy bank given what you can save on a PT.
Of course, none of this addresses issues of tone.
