Operation: Use some junk...

Nick_the_'Nole

Super Member
I have way too many extra bits and pieces laying around, and I need a preamp, so I think it's time for a DIY project. The problem is, I want to use primarily stuff I already have to keep cost down and clear up space, and I suffer a distinct case of monkey-with-typewriter syndrome when it comes to designing circuits from scratch. I could probably hammer something out, but without some direction, it'd take a long time. Maybe my approach is a little unorthodox, but the iron and ps stuff is generally one of the pricier parts of any project, so it's something I at least want to consider before I shell out a bunch of $ for all new parts. So, I'm calling upon the DIY gods for design assistance. I know I'm asking a lot here, but even just a point in the right direction would be greatly appreciated.

Here's what I would like to use, mainly the tranny, but I'd like to work in all of it, 'cause it would look awesome:
A transformer with 325-325 40ma (center tapped? Hafta make sure...), 5v 2a and 6.3v 2a windings, nicked from an old WWII Western Electric transmitter.
5y3gt rectifier, 0c3 and 0d3 regulators.
A medium sized metal chassis, about 11"x8"x1.5".
A bunch of octal tube sockets, and pretty much any resistor/capacitor or other small part I could need. All these components have tested good, so no worries there.

Really the only things I should need to purchase would be some good electrolytics and the actual preamp tubes. Preferably something octal for uniformity and looks, but it doesn't have to be if something else would sound considerably better.

Basically what I'd like is a stereo unit, switchable between line and phono stages, with maybe 40 or so db gain in the phono stage (and RIAA eqaulisation, of course). At very least, I'd settle for just a phono stage. Should I consider putting in circuitry for MC cartridges as well? I don't have any right now, but if it's likely I'll run across one in a thrift store or somewhere, it could be a consideration... Beyond that, I'm open for just about anything, including experimenting with unusual tubes.

So, does anybody have suggestions for existing designs/schematics, or at least ones I could modify to fit my needs? Or, is that tranny even worth using? If I can't build anything really good out of those parts, I'll just wait and build a cheap crappy op-amp based phono stage to use until I can afford the Bottlehead kits. But, I get the feeling this stuff has potential if I knew what to do with it...

Edit: Perhaps I should clarify, I have no trouble with the actual electronics build, as I have built a few projects before, but I'm still learning about tubes (I've done all solid state), and designing the circuit around the power supply is backwards to what I would usually do, so it's leaving me stumped on where to begin.
 
Last edited:
After doing some research, I'm inclined to go the route of the 6sl7. I assume now that the plate supply on my tranny doesn't have enough current to run all the tubes I'd need to include a line stage, so I'm going to focus on just building the phono stage I need. I found this in my searches, and it seems to be precisely what I am looking for. Has anybody ever tried it (or even Bob Danielak's original design that it is based on)?
 
Back
Top Bottom