doctord02 wrote:I have a 6AQ5 wreck-like build in the works, but have not touched in in a while...
I'm using a Ceriatone 18watt OT, and an Edcor PT (180-0-180 @250ma).
As I said, I haven't touched it in a while, but will eventually finish her up.
Doc, What could we say to spur on to the finish line??? Just kidding but it sounds like an great project that would provide some great info to leverage for similar builds. If you get the inclination, post some build shots and also document your tweak notes.
I'm inclined to do a Rocket or Liverpool type build with 2 EL95's rather than 4, in order to accomplish the same thing that Phil mentioned - all the vibe and less total power.
Phil - I'd like to follow your progress on getting that voltage ladder right... I think You've identified something really key there.
I've been picking up small power trannies from a local electronics salvage place. They seem to have a ton of them that are 325-0-325. I'm putting in a Zener at the center tap and knocking them down 50 volts or so and using them in my 7 pin amp builds... this is costing me about $30 per setup. I think you can buy the equivalent on EBAY real cheap.
Right now it's mostly just work kicking my butt. I dont have the time or energy. But eventually I will finish and I'll post the results. Chances are good you'll all get to help debug it...
RJ Guitars wrote:I've been picking up small power trannies from a local electronics salvage place. They seem to have a ton of them that are 325-0-325. I'm putting in a Zener at the center tap and knocking them down 50 volts or so and using them in my 7 pin amp builds.
RJ:
Yes, I like to buy cheap iron on eBay and have done well. You should see the stuff I got from an Arkay FL30 (a 2xEL34 amp) for a JTM45 build http://tinyurl.com/32whmw
So, the Zener is the ticket! I'm not clear how these work, but I've got a very nice tranny that runs 327-0-327 unloaded and should be around 310-0-310 with a load. Some basic math and primitive testing suggest this tranny is good for between 150-200mA.
If I do the build, I'll be posting here.
Regards,
Phil
RJ Guitars wrote: I'm putting in a Zener at the center tap and knocking them down 50 volts or so
I should freely admit that I'm out of my depth with a Zener. I'm not even sure which direction it goes, no less what value. I don't usually ask for a "gimme" but it sure would help to know. 50v is just about right or maybe a bit more would be good.
I attempted some reading on the net, but it is discouraging when the author says, "...it's obvious that..." Obvious to whom? Certainly not me!
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Thanks, this article was really good. It is written at a level I can understand. It put some stuff in perspective. I'm thinking now that it is really best to find the right PT and not try to drop the B+ too much. I"ll keep looking. I might end up with a 275-0-275. Maybe I'll just put a big fat dropping resistor in it.
So does anyone know what's up with Randall Aiken? I know he shut down production and moved to Florida, but he seems to kind of dropped off "teh internets"
Never heard one of his amps in person, but always wished he would write a book. He has such a good writing style and the technical section on his site is top notch.
He's one Clemson Tiger I don't hate (A joke, I went to USC, SC as in South Carolina, and Clemson is the hated rival).
Phil_S wrote:So, the Zener is the ticket! I'm not clear how these work, but I've got a very nice tranny...Phil
Phil,
Zener is an option, and you'll get some arguments for and against... I started using them when I began to look for ways to knock the volume down on some of my builds and found they do their job well.
I first read about this in Gerald Weber's "Desktop Reference of Hip Vintage Guitar Amps". I dunno where he got it from. On Page 222 he states that you can put a 56V-50W zener in a silver face fender and knock the voltage specs down to the Blackface voltage specs... He gives the part number *N.T.E. 5278A - a stud mounted unit and says "Insert it reverse-biased in series with the B+ center tap and ground"... I never followed what he was saying here and I think I disagreed with his choice of the diode. This diode is made in an anode to ground configuration.
It seems to me that you would want a cathode to ground diode - N.T.E. part number 5278AK (Mouser part number 526-NTE5278AK). The "K" at the end of the part number indicates a cathode to ground configuration and this is the only type I have used... I've been successful so far, thus I don't know any better. If my logic is correct, you should be able to mount the Zener directly to your chassis and all polarities would be right. That's what I've done and so far so good.
Possibly someone else has more experience and could enlighten all of us about the proper choice?
