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October 17, 2017

Fender Champ 5F1 Guitar Amp DIY Build

If you are looking for a simple guitar amp circuit with great tone and you don't need a lot of power, the Champ 5F1 is a great choice. The Champ 5F1 was introduced by Fender in 1958 and were produced in tweed covered cabinets until 1964 when the "Blackface" circuit and cabinets were introduced. The 5F1 features 6 capacitors (+1 additional bypass if desired), 12 resistors, 3 tubes, and one potentiometer. Not only is a simple circuit harder to screw up, it's easy on the wallet too! The output is a modest 5 watts, which is great for practice and studio work. There are some chunkier transformers that let you bump up to 15 watts with a tube and resistor swap if desired.

The Champ 5F1 starts its life as a turret board. If you're not familiar, these were very common in the 50s and 60s, where axial capacitors and resistors were lined up on the board. Why I wasn't alive back then, I assume this made electronics easier to fix for the visiting repairman, who could simply look at the board and see where the problem component is and replace it easily. The use of these faded as electronics were more commonly replaced rather than fixed. You can easily find one pre-made for the 5F1 on Ebay, Watts Tube Audio or buy a black FR4 board, drill the holes and affix the turrets yourself (It's fun!). You can get the tools to do that at Watts Tube Audio as well... I encourage you to support them, they are a great small business and a source for myriad board designs. 

A classic turret board

Adding the caps and resistors is easy, just ensure the leads are long enough. Some carbon comp resistors from Mouser were too short I found. The parts used here are Illinois Capacitor electrolytics and Koa Speers / Kiwame resistors. Some people prefer Sprague for the axial caps, however I've heard from a trusted source that he's experienced failures first-hand with them, so I steer clear. F&T is the only other high voltage axial capacitor maker that I am aware of. It's a niche market, so we're lucky we have three options.

Next, you'll need a chassis. While I often drill my own, sometimes it's nice to take a little break and get a pre-fab one. This one is from Tube Audio Supply and is very high quality. They supply a number of colors in addition to the typical polished/chrome, great for a personalized look.  

Tube Audio Supply 5F1 chassis in Oxblood Red

After much reading regarding transformers, ClassicTone by Magnetic Components seemed to be the best bang for the buck. I chose the 10-18019 model, 5/15 watt version for power. As you can see below they aren't too easy on the eyes, there's quite a bit of errant varnish. 

ClassicTone 10-18019

It also may have been the end of the day on Friday when they put this one together. The nylon washer broke off inside so the builder put a few lock washers there instead.

A little bit of elbow grease, paint and new screws/nylon washers go a long way. 


...too bad, as I liked their logo on the bell. Aside from the visual issues, the transformers seem very solid. 

Below is the unit with the mostly-populated turret board in place. The light is the typical Fender jewel style that I like to use on pretty much everything. 1/4" jacks are Switchcraft, and tube sockets are Belton. The pot is a high quality PEC unit from Canada, which I feel is worth the extra scratch over CTS / Alpha. 

Getting all the wiring correct is important, and a little tricky as there isn't a ton of room once everything is in place. I highly encourage you to visit Rob Robinette's fantastic page on the Champ 5F1. It lays out all the parts and their purpose, as well as optional parts. Rob is an awesome guy. I once messaged him to donate some funds for site maintenance as I was building one of his designs and he told me "just buy yourself a few beers, I do this because I love it". Also on the page are various guitar mods, headphone circuits, car tweaks, you name it. 

Next we need a cabinet to drop this puppy in. I had one custom made for me by a Jim, who goes by tubeampcabinets on Ebay. The work is phenomenal, with Spalted Maple and Purple Heart accents. I highly recommend you reach out to him via Ebay to get yourself a nice cab yourself.

Beautiful Cab from Jim, Ebay user TubeAmpCabinets

While it's not necessary, I had some spare damping material which I added to the box to prevent standing waves. 

The driver I chose is an 8" 4 ohm ceramic from Jupiter Condenser. Anyone who's followed my blog knows I love Jupiter's capacitors, they have a warm, natural tone that does music right, so I HAD to try a Jupiter driver. 

Jupiter Condenser 8" ceramic cone woofer

It's a beauty in what looks like a hammertone green powdercoat. For $50 it's a straight-up bargain, considering the caps can cost many times that. The AlNiCo versions are notably more expensive, but there isn't an 8 inch version of those yet. It will likely give me an excuse to build something a little bigger ;)

Below you'll see the unit with everything fitted, including the Red Astron Jupiter tone caps and a burgundy hospital grade power cord that I purchased from a surplus electronics store. As the PEC pot did not include a switch, I added one, a surplus Carling SPST, thus the 2 Amp fuse had to be mounted inside the chassis vs. a panel mount. 

One of the greatest things about the Champ is that there are many NOS tubes out there for dirt cheap. I got a handful of 5Y3 rectifiers and 6V6 power tubes for a song online. You'll find plenty for around $10 each. The 12AX7 is going to be a little more pricey , but still much more reasonable than say a 6922. I had a spare Yugoslavian Ei from the 80s that I dropped in, nice and smooth sounding. If NOS is too expensive, there are many good new production 12AX7s out there. I personally like the long-plate Sovtek 12AX7-LPS, which are about $15 a pop.  

Cool looking red power cord sourced from an electronics surplus shop

The knob I chose was one I had in-hand. It needed to be milled a bit to fit, but I liked it a little better than the red chicken head knob I had selected for the amp initially. 

Milled aluminum knob for a custom look

What a beauty!

The result, beautiful tone from an amp that's very easy on the eyes. 

Please remember that building/modifying circuits can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard. 

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