# just finished.....



## buckaroobanzai (Feb 2, 2006)

this puppy started out as a junked SS practice amp I found in the trash
( Harmony by Garnet Amps, so it had a little mojo anyway)

I decided to build a tube practice amp using the AX84 resources

just got her wired up, except for the Master Volume that I'm not sure I need, might add it later

also needs a 10" speaker I think, but its great for rockin' the blues around the house

I think I'm gonna bring it to Gerry's jam tomorrow, it's not really loud enough but I wanna show it off

http://i143.photobucket.com/albums/r124/cameronalx/AX84P1_2.jpg

http://i143.photobucket.com/albums/r124/cameronalx/AX84P1.jpg


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## jcayer (Mar 25, 2007)

Congratulation !!!
I built the P1 a couple years ago and really like it's sound. Master vol. is a good thing to have, 5 watts can be really loud in the house . 
Hope you'll like it as much as I like mine !!!


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## rhh7 (Mar 14, 2008)

I'd love to know more about how you did this!


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## buckaroobanzai (Feb 2, 2006)

Well, to make a short story long....

My main amp has always been a Roland Jazz Chorus 60. I'm a big fan of sticking with gear that I know works. But somewhere along the line I thought I should get some form of tube amp. Then a while back I found a derelict Harmony amp in someone's trash while walking the dog. I thought I could at least use the speaker out of it, but it was trashed along with most of the internals, but the chassis and cabinet were in decent shape. So, I thought I'd find out if I could build it into a tube amp. I have been soldering and building pedals since high school, so I figured I had enough electronics background to give it a go.

I did some searches for "DIY Tube Amp" and ended up at AX84.com. Lots of valuable information there, including valuable tips on how not to kill yourself while working with high-voltage circuits. I downloaded the documents on the P1 basic amp, and went through the bill of materials. I had a few of the components already in my pedal-building stock, but no high-voltage components or tube stuff. So, I began ordering from the various sources on AX84. The electronic components came mostly from Small Bear and Digi-Key, the transformer set from a local Hammond dealer, the tubes and sockets came from The Tube Store and the Jensen 8" speaker came from Steamco. A guy on the AX84 board was selling eyelet boards for the P1, but he's apparently out of the business now. Others have taken his place though.

I was able to modify the chassis at my work. Luckily the shop there has a set of punches and stepped drills that I could use for free. It was still a lot of work since the chassis was steel, not aluminum. Garnet Amps built the Harmony line under contract, for Sears I think, but even their cheap SS amps were built like tanks. Then it was a matter of populating the eyelet board using the the build diagrams and schematics. You need a good soldering iron, heat sinks to keep from overheating the components ( I use alligator clips), and patience. You also need to be able to read resistor color codes and capacitor values, since not every component is clearly labelled.

Once the eyelet board was finished, I mounted it in the chassis and began wiring everything up, which to me was the most difficult part. There are a LOT of wires in a small space. I also followed the instructions on proper grounding. Basically I riveted 2 terminal strips to the chassis, one at either end of the eyelet board, and connected them together with a wire that runs under the eyelet board. Then all ground connections go back to the terminal strips. This is to keep noise out of the amp.

Once the majority of the wiring was done, I tested the circuits using a document from AX84 that shows how to test everything before wiring in the transformers. They are expensive and you don't want to burn them out due to a wiring error. Then I connected the transformers and did all the voltage tests prior to installing the tubes. When that all checked out, I installed the tubes, hooked up my guitar and crossed my fingers. Thankfully, everything worked without smoking. My only problem was really low volume, so I went back to the AX84 forum and posted some details, and a couple of helpful people posted back with ideas of what could be wrong. It turned out that I had switched two of the pots around while installing them, so the values were all wrong. (the Midrange control has a huge effect on the volume of the amp, and I had switched it with the higher-value Treble pot.) Once that was sorted out, I had a working amp!

The amp sounds great, although too quiet to gig without micing. It's definitely a blues amp, it does not have much of a "clean" sound, but that's what I was going for, so I'm happy. I also think I will move up to a 10" speaker when funds allow, since the 8" doesn't have enough low end for me.

Here's some conclusions:

1) Don't expect to save money building your own tube amp. All told I have about $350 into the amp, which is about what a lot of low-watt mass-produced tube amps cost. And, I didn't have to buy a chassis or a cab, which would have pushed the price even higher. I also already have all the building and testing tools from building pedals. ( for instance I have since acquired a Crate V18 that I paid $99 for, and put $75 worth of mods into, and, as several people who were at Gerry's jam may have noticed, it sounds good and gets LOUD. However, I would not have attempted modding the V18 without the experience I gained building the P1.)

2) Check out the various people and web sites offering amp kits. For about what I paid to source all the components individually, you will get all the parts, properly labelled, and step-by-step instructions on the build. You'll also only pay one set of shipping charges!

3) Do your homework. I spent a whack of time on the AX84 site, reading through the background information, before I started any work. As mentioned earlier, carelessness or inexperience can kill you when working on tube circuits. Pedals use 9 volts, tube amps use up to 300 volts. And, some tube circuits will hold that voltage for a long time after the amp is turned off and unplugged! It's very important to ALWAYS follow the procedures for draining the voltage before working on a tube amp.

4) It's very rewarding. I now have a great-sounding amp that I built myself. Funds don't allow me to build another right now, but I'm sure I will build another one in the future.

Here's a shot of the insides - fitting everything into the small Harmony chassis was fun (not)

http://i143.photobucket.com/albums/r124/cameronalx/S5001607.jpg


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## rhh7 (Mar 14, 2008)

Thanks so much for this great short story! I admire your effort more than I can say. I read the AX84.forum, and several others. I find the whole process so fascinating. But I don't know if I would ever have the courage to tackle such a project. Your wiring in the chassis is incredibly neat!


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## kat_ (Jan 11, 2007)

Nice! I built a P1 last year. Yours is a lot tidier.


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