Some of you have seen me mention this project in one of the Stax threads. I have been working on the design of a board that will drop into a (common-as-dirt) SRD-7 and make it an SRD-7 Pro MkII (which has both normal and pro bias sockets). Using the published SRD-7 Pro MkII schematic and current production equivalents of all components. With all the wire pads in the same order as the SRD-7 board. With the exception of the pro-bias output, of course, as a new pad. I'm also considering an as-small-as-possible single-sided layout for stuffing into smaller transformer boxes like the SRD-4, or the Stax OEM units from kmart, radioshack, etc. For example, right now I'm working with Wima boxed film caps in the bias supply, but there's no reason not to use much smaller (but not cheaper!) monolithic ceramics. It's just a bias supply. 1W resistors are probably also unnecessary. I have a small stack of etched but empty boards that will work electrically but which, due to my inexperience with the process at the time, are mirror-imaged. Stupid mistake on my part. And a few of the components may not fit so well due to variance between the datasheet specs and the actual parts i got from mouser. If anyone is interested in those (for DIY transformer boxes, or maybe you're ok mounting them up-side-down or on the other side of an srd-7 or something), I could be talked into sending those out for not much more than my cost of sticking them in a sturdy envelope and mailing them. I might sell some kits or etched / drilled / plated boards on ebay. I mean, I wouldn't mind making a few bucks off this, and I've already identified the modern equivalents of the obsolete parts over in one of the stax threads here, and the original schematic is all over the net and people who are capable of making their own boards can fire up kicad or eagle and make their own board. Maybe if i move a few of these i will share transfer art at that point. With arm-twisting i could be talked into upgrading existing SRD boxes. Dunno what i would charge for that. Anyway, here's a photo of my latest prototype. Yeah, i lost the original screws . . . .