50L6 amp

[johnnyreece]

So, I recently picked up a stash of old tubes. Naturally, I went to the Google-machine, and looked at what I could do with them. When I got to the 50L6, I found this:

http://www.kirtland.com/guitar1/MA1.html

and, this:

http://ampgarage.com/forum/viewtopic.ph ... 608007e0d0

It seemed like a good budget build, so I threw a parts list together. Spent around $50 for a working chassis. Not bad! It's a grindy little fella, but I'm okay with that. I bought enough parts to make like four of them, and they're cheap enough I can give them away as presents. Anyhow, in building this, I noticed an error on the schematic. I also didn't like the input jack setup, so I changed it. I figured I'd go ahead and do a layout, since the prototype is put together, and seems like a keeper. I've not proofed it yet, but there's not much to screw up...I've lovingly named it "Deathtrap", as the design is similar to the no-PT designs of yesteryear (note - I do have a PT on this, so the name isn't exactly appropriate).

[johnnyreece]

Pics (lip is cut off on the front so I can add a faceplate) :
[IMG768]http://i218.photobucket.com/albums/cc165/moto_xxx199/Amp%20designs/3445F9B6-4C29-45C7-BD20-B3AF0D0E945B_zpspfgrcgdb.jpg[/img]

[IMG768]http://i218.photobucket.com/albums/cc165/moto_xxx199/Amp%20designs/C6A1CDCA-A4CF-4174-BEFF-94F37A5D4D58_zpsq82uif6o.jpg[/img]

[LOUDthud]

The layout is missing a ground in the power supply. Are you using a terminal strip with a grounded center lug?

Pretty slick design using a 240-120 PT and a 70V transformer for the OT. What is the Watt rating of the OT and what tap are you using?

[johnnyreece]

Thanks! Yes, the terminal strips I'm using have the center lug grounded. The program is a touch limited, so I was unable to easily show that. I'll update it to make that clearer. I got the idea about the Bogen from this site:

http://makearadio.com/misc-stuff/t-725.php

He says it should be good "for a few watts at best". I can't imagine this being more than a few watts...I used the taps that got closest to 2,500K for the primary with an 8 ohm secondary. I've not played it for a ridiculous length of time or anything, but it seems that everything holds together fine. Definitely worth the $50 investment.

[LOUDthud]

It wouldn't take much to make a push pull amp using the same idea for the power supply, just add one 50L6 and another 12AX7 as a phase inverter. Use a Hammond 125C or 125D as an output transformer and connect the speaker where you get the most output.

[johnnyreece]

Yeah, I've thought some about wiring the PT up as intended, and getting ~120V on the secondary and running more tubes. Or, I suppose one could keep the power section the same and attempt it with 25L6 tubes and swapping to a couple 6SL7 for the pre/PI. I've not done the calculations on that PT to see if it would hold up, though.

I just really wanted to see how cheaply I could put together a tube amp. I think this is about as cheap as it gets, unless one buys a basket case amp that just needs a little TLC for a good deal. This is my "if I meet a good kid learning to play guitar who has no money, I'll gift them one of these" kind of amp. This one is actually destined for my uncle as a surprise gift. He hooked me up with some guitar gear when I was a kid, and recently helped me get a roof on my house. He also let me experiment on his guitars when I first got into finishing. He's a total gear junkie, so I'll add to his pile. He doesn't have any straight tube amps yet, so I need to finish a cab for this so he does.

[johnnyreece]

Here's what I was able to get done this weekend. Still need to Dremel the faceplate and trim down the volume knob, but it's close enough for an update pic.

[IMG768]http://i218.photobucket.com/albums/cc165/moto_xxx199/Amp%20designs/4A00705C-2286-4E81-A250-3364213089C3_zpszefpmjvd.jpg[/img]