Hi Paul,
I don't know how many dictators create these tapes, but wouldn't it be more cost-effective and less of a hassle to have them either buy a handheld digital recorder or perhaps if there weren't a whole lot of dictators, you could furnish them with one? Maybe you could give them $100 off their next bill if they get one. You can buy compatible handhelds (not every handheld is appropriate for voice files, so do your research)very inexpensively these days--for around $100 US.
I've not personally wrestled with this issue as I have not had my own clients in a few years, but if I were starting up again with clients I would definitely have a digital setup--I would guess you would recoup the money laid out in a very short time if you are picking up tapes or even mailing them.
Check out this link on
Medword.com for an explanation if you need more information:
http://www.medword.com/digital-transcription.html Hope this is helpful!