My Fender Champion 600 Mods

Fender Champion 600 Modifications

The Fender Champion 600 amplifier is a great little recording amp, but in my experience the stock unit is not quite good enough. The reasons for this are mainly personal taste, but one or two I believe are big factors in getting a useable recorded sound out of it.

First of all, here are the mods I made to my Champion 600 and then I’ll go into more detail:

  • Replaced preamp and output tubes.
  • External speaker cabinet for recording.
  • Modified the circuit (voids warranty!).

Replacing the Tubes

This part is simple and non-destructive. It is also fun if you like scrutinizing sounds, which I do!

As soon as I took delivery of my Champion 600 amp and plugged it in I knew it could benefit from new valves. The ones that came with it sounded pretty poor to me. I went straight on Ebay and had a look around for good-quality output tubes.

Of course I didn’t know which of the two tubes in this amp (one 12AX7 preamp tube, one 6V6 output tube) was influencing the sound the most, but seeing as I like to turn the volume up high I started by buying a replacement for the output tube only. Remember, this is a cheap amp, so part of the fun for me was to improve it without spending too much money. It seems crazy to spend the same cost as the amp again to make it sound better. You might as well buy a better amp to start with!

I found a pair of NOS Brimar 6V6’s on Ebay in the UK and they were a crazy price. Something like £10 for the pair. I only needed one and incidentally a friend of mine had bought a Champion 600 the very same week as me, so I gave him one as a gift. I noticed a difference right away with my Champ. Noticeably better. Fatter, warmer, rounder and with some extra midrange, which made it seem louder. It was much less of a harsh sound. My friend thought it was a great improvement too.

Modification number one then was a success – £5 for a “real” output tube! Bargain.

With a step up in sound such as this I decided it was worth locating a better preamp tube too, but first I remembered I had an old valve Fidelity tape recorder from about 1960 lying around and not working properly. It had a 12AX7 in it and it was an original Mullard – Great, one of the best valve brands ever made. Unfortunately it was well past it’s prime and it didn’t sound that great. It had a nice tone, but it crackled a lot and was obviously close to becoming a deceased valve!

I found an original Brimar 12AX7 on Ebay and it was more expensive then the two 6V6’s I had bought previous – about £15 I think. After the positive Brimar experience I had with the 6V6’s I bought the 12AX7 (ECC83) and again experienced an impressive step up in tone quality. This actually was more noticeable difference to me.

Summary: Well worth changing the tubes. There are only two of them, so it’s cheap and fun.

External Speaker Cabinet

I thought about replacing the speaker in the amp and I may do so in the future, but this will be just for messing around. For recording I wanted a truly pro speaker and was still conscious of keeping the modification cost down (mostly for the challenge and, again fun!). Fortunately I already have another amp: A Fender Princeton Recording Amp. Seeing as this already has had an upgraded speaker, a Tonetubby Alnico 10″ (My absolute favorite guitar speaker), I thought I’d try it through that.

It’s not a perfect match because the Tonetubby is an 8 ohm speaker and the output of the Champion 600 is 4 ohms, but it safe to use. I think the result is that the volume of the amp is a little less than if the impedances were matched. It sounds really great through this speaker – In fact everything sounds amazing through this speaker. It’s expensive, but worth every penny in my opinion if you are serious about guitar tone, especially in the recording studio. The 10″ Tonetubby has as much sonic girth as a 12″ speaker with the detail of a 10″.

The best way I can describe the benefits I get from using this Tonetubby speaker is to use the following analogy:

It does for my guitar tone what a quality tube mic preamp and analogue tape do for digital recording. It takes off so much harshness and presents you with so much clarity, you can actually listen to the top end. The sound doesn’t fly at you like a beam of treble! It goes around you so you can listen to it rather than have it thrown at your ears.

Bottom line, try out a few speakers or just go to your favorite one. A bigger speaker will make the Champion 600 sound like a bigger amp.

Circuit Modifications

This was the most labor intensive modification and actually involved me hacking away at the internals of the amp; not too much, but it did void the warranty, which is understandable. I’m not an amp tech, but I can read instructions and use a soldering iron. I also found it fun to do this, but if it had been a more expensive amp I either would have got a professional to do the work or not bothered with the mod. at all.

There are many different after-market modifications for the Fender Champion 600 amp available now, but I went for one that seemed simple, practical and was based in the UK (where I’m from). I went for the “alnicomagnet” mod kit on Ebay, which is excellent, fairly easy to fit and comes with a really good instruction guide on CDROM. This modification does a few things:

  • Greatly reduces hum.
  • Sorts out the voltage supply discrepancies for the UK-spec model
  • Modifies the tone stack to 5E1 or 5F1 Champ specs (late 50’s model)
  • Adds a 3 position switch for standby and selecting between Pentode/Triode operation (2watts or 5watts)

This amp is greatly improved after these simple mods and now, through the 10″ Tonetubby, it can get close to a Tweed Deluxe tone – to my ears anyway, which considering the cost is a fine, fine result!

I love my Fender Champion 600. I will post some sound clips soon too. If you use an external speaker, it is a great recording amp, but I find that there is still sufficient hum audible if you close mic the built in speaker. However that may just be my amp. My friend’s Champion 600 had a better stock speaker in it, which didn’t crackle like mine does (before and after the mod).

39 Replies to “My Fender Champion 600 Mods”

  1. I too bought a Fender Champ new in May 2010 and immediately swopped the stock Fender Design speaker for a Jensen MOD 6-15. The preamp 12ax7 was a Sovtek (so I kept it) but the power 6v6 was cheapo Chinese, swopped that for a JJ 6V6S. Mucho bueno! The other problem I dealt with was the soft flannel type grill cloth. It was too dense and didn’t breath; it vibrated like a trampoline at higher volume, creating an annoying buzz. Swopped that for outdoor furniture type material (looks like nylon tweed). Much better. I also thought this little baby ran very hot, but consider that all of the internal parts are so close together. I would like to find an appropriate external speaker cab for this model.

    1. I’d be interested in hearing what the Jensen MOD speaker sounds like. I have been trying to pursuade the guys at Tonetubby to make a 6″ hemp cone speaker to fit the Champion 600. They already make a 8″ version, but it’s too deep to squeeze in I think.

      The only thing that put me off getting a new speaker was the fact that I hardly use the stock speaker anyway, because the hum is still a bit too loud for recording tha amp, so I’ll stick with my 10″ Tonetubby alnico in the extension cab for now.

      Congrats on your amp aquisition! It’s an amp of extreme coolness for sure!
      Rob

  2. The weber speaker makes nice replacement. The jensen takes about 60 hour of playing to open up. Most people will not wait that long.

    1. 60 hours of playing…. Borrow a looper pedal (or if you have a boss dd7/Line6 DL4) throw a loop on Go to work and your set!

  3. Much cheaper mods than this. Probably much bigger difference in sound also. Check out lifting the tone stack resistor and also lifting the neg feedback resistor. Goes from meek and cultured to a drunken wildman. Very Jekyll and Hyde. But do replace the 6v6 before you run both mods at max. A cheap tube can fry and short the output xformer.

  4. That is such a great write up! Many thanks for the effort
    Got my second hand Champ 600 off eBay today and am already thinking about the valves.
    How do I know which ‘vintage’ valves will fit? (sorry if this is a dumb question but I never even had a valve amp before)
    Thanks

    1. It’s pretty simple really. There are only 2 valves – one preamp valve and an output (power) valve.

      The preamp valve is the most common on the market: 12AX7 (also known as ECC83).

      If you want the amp to have slightly less gain and distort less then you can try putting a 12AY7 in there instead.

      For the power valve – a 6V6. This is the same valve used in many of the smaller Fender amps, like the Deluxe, Champ, Princeton etc. They are some of the most readily available valves around. Be careful if you are buying old valves as there is no way to know for sure the condition of them, so don’t pay high prices if you want to experiment.

      A good choice, when buying new ones is the brand “JJ”

      Congrats on your amp purchase. You’re now in the cool club!
      Rob.

  5. Hey- cheers Rob…really appreciate your reply!
    Right, I think I’m ready to dive in to eBay and have some fun with a few old valves (I see some sellers list them as ‘tested’ etc so I’ll stick to those)
    One last question (which is a bit lazy as I could take the front off and check myself) but when people say it is a 6″ speaker, is it 6″ diameter?
    The reason I ask is that I have seen some nice vintage speakers on Ebay too, but they are oval shapes and the smaller of the 2 diameters is 6″ (e.g. 6″x10″ or 6″x8″)
    Does it have to be 6″ diameter and perfectly round to swap out? Or would any of those mentioned about fit?
    Thanks for your help!

    1. I’m not sure how easy an oval speaker would fit in there. The difficulty is that speakers external dimensions vary from brand to brand.

      The speaker cone in the Champion 600 is 6″ I believe and the hole in the baffle is the same shape and size as the cone. Also the space in the cabinet for a larger speaker is the thing to watch out for. It may be possible for an 8″ speaker to fit diameter wise, but the hole in the front will obstruct some of the cone and the depth of an 8″ speaker (the magnet etc) may not fit into the space behind the speaker due to the chassis of the amp.

      It’s going to have to be a case of taking as many measurements as you can think of inside the cabinet and trying to find out the dimensions of the corresponding parts of the replacement speaker.

      Maybe somebody else reading this has some experience of changing the speaker in the Champion 600.

  6. Yes, I’ve got you…a bit of trial and error no doubt.

    I have a couple of old reel to reel tape players that I don’t have much use for except to fill out the loft.

    I might see what speakers are in those , and possibly check out the valves too.

    Thanks for all your help with the great blog.

    1. Those old tape recorders can provide hours of fun and some great tones. Depending on the age they’ll probably have alnico magnet speakers in there. They work great for guitar.

      By the way, if you do any interesting mods to your amp and you want to write an article for the site then please get in touch (under the “contact” tab in the menu).

      It’s always great to hear from people into the same crazy stuff as me. Best of luck with the Champion!

  7. Change the tubes!
    Easy and so much better!
    The hum is reduced, the sound is bigger and louder:

    The new TAD 6V6GT-STR – made the biggest difference.

  8. I have a really excellent champion 600 mod and DIY mod program that you might like to check out…this is what the Fender Champion 600 sounds like after a Fargen Hot Mod:>)

    Cheers,
    Benjamin Fargen
    Fargen amps Inc

  9. I am going to replace the transformer (http://shop.amppartsdirect.com/Upgrade-Fender-Style-15W-Output-Transformer-40-18031-40-18031.htm).

    I did some tone stack mods (removed the resistor, some caps, etc.)

    I am looking at replacing the speaker for an 8” and was hoping anyone might be able to lend some advice. Namely there is the Weber speaker hosted on the amppartsdirect store.

    (http://shop.amppartsdirect.com/Weber-Signature-8-8ohm-Ribbed-Cone-Alnico-SP-8SIGA8S.htm).

    Also, I was looking on ebay, at something like this Jensen.

    (http://www.ebay.ca/itm/Vintage-Jensen-8-Speaker-C8R-220318-/330602318164?pt=LH_DefaultDomain_0&hash=item4cf96f0954)

    I just figured I would see if anyone can give some relevant reccommendations. The band plays quite trebly pop music.

    1. I haven’t replaced the OT. I’m sorry, but I’m not much a real amp tech, just a tinkerer and I don’t know what the problem could be with your OT.
      Hopefully somebody reading here can chime in.

      Have you googled “BillM mods”? He is well known for modifying the Blues jr amps among others. You may be able to contact him for advice.

  10. To the moderator: feel free to disregard and delete my comments (sorry). They’ll contain outdated links soon enough, and I have already researched and purchased the parts I was asking about. Your site was a great help, thanks for putting it up!

  11. Hey,

    I was wondering, have you applied the triode/pentode mod?
    I’ve seen this on a newer amp, like the Ampeg GVT5H. Which has a low power mode AKA Triode switch.

    How hard was it to apply? Seems like this would make a huge change to the tone and response and everything, so I’m quite interested in the results 😉

    1. Well technically I suppose you would need to, but I’m not that technically minded and I haven’t had it done for me.

      I think on an amp of this size it is less critical than a higher powered amp. I doubt it’s hugely important, but somebody might be able to correct me on that.

    2. Are the tubes easy to replace ( I have never done this ) Can anyone please give me instructions .Also On my amp the volume pot crackles I have sprayed it loads of times but still the same any Ideas what else to do .

      Regards Mark

  12. To avoid Hum in the Fender Champion 600, it is a good idea to move the output transformer away from the main transformer. thats help a lot.

    1. Hey Jorgen, Do you have any photos you could send me to show how/where you moved the output transformer?

      I’d be very interested to know the details. Thanks for the comment, looks like it helped out another reader of the blog.

      Cheers
      Rob 🙂

  13. Jorgen:

    Thank you for the tip on moving the output transformer. It was free and easy hum reduction. The change is remarkable.

  14. Rob:

    1. Unplug the amp.

    2. Remove the back panel.

    3. Remove the 6V6 tube.

    4. Remove the amp from the cabinet.

    5. Follow the output transformer cables into the chassis. Notice two zip ties.

    6. Cut said zip ties.

    7. Remove the output transformer screw closest to the power transformer. Slightly loosen the other output transformer screw.

    8. Pivot the output transformer on the remaining mounting screw so the empty mounting flange comes as close to the 12AX7 as you are comfortable.

    9. Tighten the single screw. The transformer isn’t going anywhere.

    10. If you’re especially diligent, mark and tap the chassis for installation of the second screw.

    11. Reverse, and button her up.

    1. Thanks for those instructions. I was considering selling my amp as it doesn’t get that much use anymore, but I’m tempted to try this now to see if it improves the performance for recording purposes.

      Cheers.

    2. Glad to help, Rob. You absolutely must change the speaker grill cloth. I think Fender found a good deal on old clipper ship sails, so they put them in this amp.

      Goodwill is a good source for really cheap fabric. Find a very sheer woman’s garment in whatever color hits you; pay $1.99 for it, and presto! Cheap grill cloth.

  15. FWIW, I do not like the Tung Sol 12AX7 in the C600. Even in the Low input, it’s far too trebly. I have a Bugera 12AX7A I stuck in there, and the tone is much mellower, usable and friendlier.

    If only I knew who made the Bugera 12AX7A.

  16. One more thing: leave the back off. It seems any hum finds the cabinet and semi-closed back a resonant chamber and soundhole.

  17. I am interested in the changing the voltage from 230 to 240 UK, how hard is that to do? Does it require me to solder parts?

    Thanks Michael

    1. Hi Michael,

      The mod kit linked in the post includes that very modification. It’ll convert it to a proper 240v spec.

      Thanks.

    2. Thank you, however I have talked to Nigel via email & the amp I have has already had a custom conversion so his kit is no good, I will do the output transformer mod as amp has some hum

  18. hey guys,
    been working on the Champ and just got the 40-18031 output transformer and a Weber Signature Alnico 8 speaker.. the thing is that I have installed both, ( the OT is wired on 8K primary and 8 ohms secondary to match the speaker)
    I’ve turned it on and without any input and the Vol at 0 it started making a high pitched noise, like a squeal … what’s the matter? really appreciate any input

    1. Reverse the two OT primary leads (red and blue). It’s likely that they are now hooked up in the wrong polarity.

  19. It’s been really great to see how this conversation has developed regarding this little amp and I’m happy to see so much support for each other regarding troubleshooting, advice and tips.

    I sold my Champion 600 a while ago now as it really wasn’t getting any use. It’s gone to a happy home and the new owner is pleased with it, so that’s all good.

    Please continue to contribute to this thread if you have anything worth sharing and thanks to all those who have taken part in the discussion.
    Rob

  20. I love this little amp. Anyone know more about using a larger external cab? I have an old bass cab with a 15, and the champ will drive it, but with less bite and volume than the 6″ speaker, as you might expect. I’m thinking about using a Y splitter at the speaker out to run both at the same time. I figure this might push twice the air and work like a woofer and tweeter, with maybe clean lows and broken up highs. The 15 is 8 ohms, and the champ is 4. I’ve heard conflicting info- can this damage the amp long term? I’m sure it won’t damage the speaker. Any knowledgeable help is appreciated.

    1. Hi Russ,
      You should be fine with an 8 ohm cab. I used my Champion 600 with an 8 hm Tonetubby for years without any problems.

      It’s normally more harmful if you use a speaker that is lower impedence to the rated output on the amplifier, but I’m not sure it would be a good idea to go as far as using a 16ohm cab with the Champ.

      Let us know what it sounds like if you try it or post a clip on Youtube or something.

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