My First Guitar Amp

About 2 years ago I decided it was time to cobble up a guitar amp using as many parts as I could find on hand. This included a transformer and choke from a short wave radio (ca. 1968) and an electrical junction box I found rusting under a house. The balance of the parts I ordered from TubeDepot and Triode Electronics, which both have a great selection and aren't too pricey. 

Though I could have gone (and maybe still will) with a solid state rectifier and bumped up the B+ voltage to really get the EL-84 tube screaming, I decided I would build it like they made them back in Olden Tymes and went with the EZ-81 tube rectifier. Going one step further into simplicity I only used one side of the 12AX7 preamp tube as well. I really just wanted it to work when I powered it up without worrying about wild oscillations so I pretty much stayed within the printed tube specs. Later posts will reveal my second creation which does push some of those limits so stay tuned! 

How does it sound? Nice and clean but not too bright. With a preamp pedal pushing the level a bit it breaks up pretty well too. After the break check out the innards as well as some schematics. 

Here is the guts. On an amp this small I could have wired it point-to-point but I really wanted to use a turret board for some reason. Notice the choke from the old radio on the right. I also used cloth wire just to give it that vintage wire tone. 

More insides. You can see the star ground at the bottom right. To get that perfect bias point on the EL-84 I had to parallel up some resistors.  

When laying out the transformers I used an old timer's trick to reduce hum. While the power transformer was powered I hooked a set of headphones up to the output transformer and placed it where the least amount of hum was, within reason. 

An earlier layout drawing where I thought of putting the choke on the top. 

And the schematic done in gschem an open source electronics design software suite.