Big Champ

photo 3.JPG by jimmyrocket02
photo 3.JPG, a photo by jimmyrocket02 on Flickr.

All amps are iconic in their own way, but in many ways collectors of the early ’50’s tweed Fender Champs have elevated them to cult status.

Originally conceived by Leo Fender as a “practice amp,” the circuit is about as simple as it gets ( 12AX7 / 6V6GT / 5Y3 ) and has a bevy of close cousins in the small amp world, but the magic of the champ for many has been its imminent recordability. Despite the small size, Champs can sound huge in a recording studio, not to mention raw, visceral, touch sensitive and harmonically rich.

I’ve built several models of the champ and have found two of them to be particularly to my liking. The ubiquitous 5F1a and its predecessor the 5C1.

The one point of contention among purists is the size of the speaker. Original 5c1 champs came with a 6″ speaker and 5F1 champs came with 8″ AlNiCo speakers, but I’ve seen them built with anything from 6″x9″ speakers to 2×12″ speakers. Vintage folks argue anything other than the 8″ and it loses that “champ sound.” They may be right, but there are a whole lot of other great sounds to be had with this circuit as well!

This is a custom build with a 5F1a circuit in a pine cab extended nearly to 5E3 size to accommodate a vintage 12″ Heppner speaker.  The circuit itself has a few mods. .01 Mallory coupling caps and a blocking resistor on the screen of the 6V6 to tighten the bass and make it play nicer with humbuckers. Mojotone (power) and Classic Tone (output) transformers bring this to life

The box is finger joined pine, covered in vox style “fawn” tolex.


 

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10 thoughts on “Big Champ

    • Sure Jonathan, let’s talk! Although you may be better off doing it as a 2×10. I modified the circuit in this one to be able to handle the 12″ but Champs can get a little flabby on the low end with 12″ speakers, and 2×12 would be testing it’s limits.

      The real issue is that it takes a lot of power to accurately reproduce low end (which is why bassists are always carrying several hundred watt amps to keep up) and at 5 watts the champ will probably struggle to push 2×12 drivers. You could put 2 high efficiency speakers in there, but you would really lose the lovely character of the Champ’s distortion.

      Issue #2 is that the circuit of a champ is made to attenuate some of those frequencies for the reason listed above, and because those original 6″ and 8″ speakers sounded pretty terrible if you pump too much bass into them.

      Long story short, is that while a 2×12 champ sounds like an awesome idea, you’d be better off putting something in that box that can put out at least 10 – 15 watts

      A champ in 2×8 or 2×10 format, however, can sound divine.

      In fact, just thinking about the 2×10 makes me want to build one 🙂

  1. I am now in possession of this wonderful little amp, just curious on the heppner speaker, do you know how many ohms it is? I didn’t find anything written on it, just curious in case I decide to swap it out later on. It’s a sweet amp, I bought it as a backup to my Port City Twelve (or to run stereo when given the opportunity), but now I have a hard time choosing between the two when I can only use one amp.

    Thanks,

    Rob

    • Rob,

      Glad to hear you’re enjoying it! That certainly is a special amp with a unique sonic signature.

      The speaker is an 8 ohm speaker rated (conservatively) at about 15-20 watts. I tried several and found that to be my favorite match for the amp, but just in case you do decide to experiment make sure you pay attention to the dimensions of the speaker. Certain “British” frame ceramics would have a hard time fitting in there because of depth. It was a trade off to get everything in a nice tight package, but most alnico Jensen-type speakers will slide right in there.

      I’m looking into a 2×10 version after I finish my next two builds. I’m just about finished with one now that is a head with a 1×12 cab based on an obscure Silvertone design and I’m doing a Matchless spitfire in a 1×10 combo after that.

      • If I put new tubes in the Big Champ, does it need to be re-biased? Any tube recommendations? I like JJ’s, but thought I’d ask you since you built it.

  2. No need to re-bias. It’s a cathode biased amp so it’s self biasing. In fact, although it wouldn’t be running at optimal specs, it’s even safe to run a 6L6 in there if you want.

    Lot’s of folks like JJs but my personal favorite new production tube is Tung Sol. They have a really great 3D quality to them.

    If you do put new tubes in there, you don’t need to replace the rectifier, just the 6v6 and the 12ax7. If you’re looking to do some tube rolling, you can try a 5751, or a 12ay7 in that preamp for less gain. I love NOS 5751s in champs.

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