RossD
RossD UberDork
12/26/12 7:54 p.m.

I started looking for small tube guitar amps and the Fender Champ seemed to me to be what I was looking for. But with a price tag, that they seem to go for, I wasn't willing to pay for an authentic one.

So after looking at kits and and the diagrams, I decided to build my own without a kit.

Once I bought the right parts and a piece sheet metal, I tried a layout:

Cut some holes with a drill, jig saw and a die punch from harbor freight:

After some thought, I came up with a cabinet design made out of an old shelf that I took down from the basement:

I then populated the chassis:

Then solder in the capacitors and the resistors. Here you really have to take your time and study the schematic:

I actually broke the volume/power pot before I ever put electrons to it, so I had to replace them and I separated the two features:

Here is the assembled unit:

That last picture is actually one step a head of my little build timeline. The first time I powered it up with no input and no volume, the speaker squealed after the tubes heated up. I checked the diagrams of the output transformer and realized I had the wires switched and instead of negative feedback, I was getting positive feedback. Checking with other build treads, pointed me to the checking the output transformer.

After that one little correction, I had my droid phone playing music through the amp! It sounded delightful

I checked my voltages at the output of the rectifier, after the 10k and after the 22k resistors and they seem okay.

I then plugged my guitar in and jammed out. It has nice volume and breaks up nicely.

I still have to do some finish work, like mount the chassis and soundboard permanently and wrap the cabinet with some guitar amp type stuff. But hey, it works!

Part of the reason I wrote this up and documented what I've done so far is to encourage others to try something new. I've never built electronics before but I did a lot a research on how everything works. I'm still learning but I've come a long way since just wanting to buy an old tube amp. I'll be finishing up this amp in the coming weeks and will be starting a stereo tube amp for Hi-Fi use, but that's likely a couple months off yet.

-Ross

N Sperlo
N Sperlo UltimaDork
12/26/12 8:00 p.m.

Wow. Impressive work.

banzaitoyota
banzaitoyota New Reader
12/26/12 8:08 p.m.

It was a cheesy lil amp with a sign on the front that said fender champ........

David S. Wallens
David S. Wallens Editorial Director
12/26/12 10:24 p.m.

Very cool--and little tube amps can be fun. I have a 2 watt Fender Greta. You can crank it up without blowing out the windows.

ransom
ransom SuperDork
12/26/12 11:29 p.m.

Compelling stuff, as I find myself looking at spending more than you probably have in that amp on an attenuator to bring my Twin Reverb down to non-police-intervention volumes while working hard enough to sound good...

chandlerGTi
chandlerGTi Dork
12/27/12 6:41 a.m.

So, what did that run. I've had a fender hot rod deluxe that I borrowed (he is wanting it back), so I'm looking for a cheapy to replace it.

RossD
RossD UberDork
12/27/12 7:35 a.m.

RE David: I have a Greta, too. I'm really impressed with it but it doesn't have much head room.

The cost of the two transformers, speaker and the three tubes are the major parts. ($44 power trans, $19 output trans, $10-15 per tube, then all the other parts are around $0.50 to $3.00 for single caps, resistor, tube socket...) The speaker was $40. Most of the parts came from Triode http://triodeelectronics.com/index.html

The thing that can creep up is shipping cost of all the little bits. So I ordered one or two more of everything small.

I'm guessing I'm under $200.

Some of the stuff can be bought at Radio Shack. After I started learning about tube amps, I started looking at garage sales and antique malls for anything with tubes. I'm actually not using my new tubes I orderd but some old ones that I got in a box for less than the cost of new ones.

If I were to start again and make the same amp, I would have taking more time making the cabinet. I would have used a different type of metal for the chassis as I bent it some by drilling and cutting it. The laydown power transformer recessed hole would have been easier if it was a stand up one like the smaller output.

(Frank Zappa )

Here's a link to larger images if anyone wants a closer look.

I got this idea in early summer and I just finished it now. It was definately a hobby that I would visit with time permitting, but I did do a lot of studying of the schematic and reading everything I could find on how this stuff works.

David S. Wallens
David S. Wallens Editorial Director
12/27/12 1:35 p.m.

Yeah, true, the Greta has its limits. Still, it looks neat and doesn't rattle the windows. And when I want to make more noise, I fire up my real amp. Last night I nearly found the brown note.

Tim Baxter
Tim Baxter PowerDork
12/27/12 1:55 p.m.

The champ's dirty secret is that like almost all small amps of the day, it was basically straight out of the then current GE "amps for dummies" book. Which doesn't make them any less awesome. Nice work, building your own. I wouldn't dream of trying it without a kit, myself.

I'm a big fan of small amps, myself. My fave was made by a guy named Jimmy Dula from old PA systems. It's 5 watts, class A, with a 12" speaker. I swapped the 12AX pre-amp for a 12AU, so it actually has quite a bit of headroom, and it rings like a bell.

RossD
RossD UberDork
12/28/12 7:39 a.m.

RE David: E36 M3! I still have my Hughes and Kettner Attax 80, 100w solid state head and Fender 4x12" cabinet, but since I just jam out by myself at home, it's quite overkill. That and no one wants to buy half stacks anymore so it's damn near worthless.

RE Tim: I wanted to do a 12" speaker but I also wanted to keep it lower price so I went with a Jensen Vintage Ceramic 8", 8 ohm.

I want to make a hi-fi stereo tube amp next, but this will probably be the project after that: It's an old Webcor that was meant to be an extra amp/speaker for a record player.

RossD
RossD UberDork
1/6/13 3:05 p.m.

I had some intermitten crackling and after poking around with the amp on with a wooden skewer, I'm guessing it's coming from the 6V6 tube. I tried all of the new tubes I bought for it and it seemed to get rid of the random crackling. I'm still doing testing of it and haven't had much chance to spend time playing through it yet either...

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