Introducing the One And Only (Unofficial) Fender "ChampTone 764"!...

Discussion in 'Amp Central Station' started by AxemanVR, Apr 19, 2018.

  1. AxemanVR

    AxemanVR Tele-Afflicted Ad Free Member

    Dec 27, 2011
    Minnesota USA
    The evolution of this amp project has been covered in an earlier thread here, but now that I have finally completed about as much as I probably will on it I decided to provide a more condensed overview of my new creation...

    Way back in 2009, while on vacation in Hollywood California, I bought one of these ever so popular Fender Champion 600 reissue amps:

    01 C600 original.JPG

    I got it at the Guitar Center on Sunset Blvd - and, yes, I did go to the "Sunset Grill" afterwards (yummy).

    02 GC HWood.JPG

    I also paid $200 for the baby Fender - right before the retail prices dropped to $150 (doh)!

    Anyway, fast-forwarding to July 2017 you'd find the little C600 collecting dust and well on its way to being put on the chopping block, but then, for some unknown reason (divine intervention?) I decided to give it one last chance and discovered that it was actually an amazing little amp - once I figured out what it takes to make it work!

    Long story short:

    There were ultimately several things that changed my amp from being somewhat pathetic to being something that oozes classic tones out of every pore, but there were two things in particular that (initially) played a significant role in changing my view on the C600 and they were tubes and matching speaker.

    Ok, so that's not exactly earth-shattering news, but finding the right combination of these, and a few other parts, to make it a "total package" was the real trick.

    In the end, after much swapping of various high and low end components (including some vintage stuff), what surprised me the most were the fairly run-of-the-mill parts that actually ended up working:

    An Electro-Harmonix 12AX7EH preamp tube...

    03 12AX7EH.JPG

    ...a Mesa Boogie 6V6GTA power tube...

    04 6v6.JPG

    ...and a plain-jane "Specially Designed For Fender" Eminence 12" speaker...

    05 Speaker.JPG

    I was nothing short of amazed at the tone I was now getting. In fact I liked it so much I decided to make my own custom chassis and put everything into a larger gig-worthy cabinet (a Princeton 65):

    06 Chassis.JPG
    07 Chassis in Cab.JPG

    I did do a few circuit modifications as well...

    Besides moving and rewiring the transformers to reduce noisy interference I also installed Nigel Briggs' "Alnicomagnet AA764 mod" (off eBay) to further reduce the excessive hum, hiss and buzz that originally plagued this amp (works great, thanks Nigel!). I then added a full-sized standby switch (the one supplied in Nigel's kit was way too micro for me). On top of all that I added pots to the tonestack so I could adjust the Treble and Bass - although the range of the Bass control is very limited, so I may have to experiment with some cap or resistor combinations later. Adding a treble pot definitely makes a huge difference though.

    08 Circuit.JPG

    Well, all this hard work was well worth it and I now have about as vintage sounding an amp I think you can have using modern components and I am more than satisfied with the final results.

    Anyway, since Fender based the (reissued) Champion 600's circuit on the 1964 AA764 "Champ Amp" and since I also installed it in a Princeton cab, I was initially going to call it the "ChampTon 600" - but that sounded lame - so I renamed it "ChampTone" and - upon discovering that the "600" in "Champion 600" originally referred to the 6" speaker size (and I am now obviously utilizing a 12" speaker) - I decided to go with "764" to reflect the circuit design instead, sooo...

    I hereby present to you the amazing (old-ishly-new) blackface "ChampTone 764"!:

    09 ChampTone 764.JPG

    So, how does it sound?

    Since I don't have a vintage Blackface Fender to do a direct side-by-side comparison to, I'll just describe its tonal attributes the best I can here:

    Overall it has a full, rich, fat sound with a distinct, sort of "boxy" compressed high end, which keeps things sounding smooth while still retaining ample amounts of clear, bright, glassy and sparkly tone. The midrange sits in a comfortable spot for most guitars, not being to soft or bold and the bottom end is tight and never flubby - all of which is a testament to the the Fender/Eminence Speaker's compatibility as much as anything else as far as I'm concerned...


    Most Importantly; This amp is blessed with that ever so satisfying, highly coveted. lively three-dimensional "halo" that allows the guitar's tone to literally "glow", which is what I believe most people perceive as a vintage amp's "magic" and, when paired with a well matched instrument, this is no doubt what makes my ChampTone 764 really sing!

    It also works well when pushed...

    A brighter humbucker helps to keep things sounding clearer when cranking the gain on this amp and when I plug the Seymour Duncan "Pearly Gates" bridge pickup I have on my HSH Strat into a tubescreamer style pedal, this little amp really screams! Clear and articulate with a smooth crunch.

    When using a clean booster pedal the ChampTone's natural clipping also provides a healthy dose of crunch, although this overdrive has a harder edge that can't be easily dialed out without making things too murky, so I actually prefer the smoother, sweeter, clearer edge of a nice warm overdrive pedal when needing that sound on this amp.

    It has a wider "sweet spot" range than I originally gave it credit for as well... between 5 and 8 on the Volume knob, which I assume has to do with its single ended Class-A design.

    It can sometimes get a little thick when set above "8" on the Volume knob (especially while playing clean) but not to the point of being unusable - although I tend to stick to my brighter guitars (like a Strat or Tele) when cranking it all the way up. Lower than "5" isn't all that bad either and it can get whisper quiet for bedroom jamming and still sound nice, although you'll definitely notice more floor noise at lower levels (but it's not too bad either since my upgrades - thanks again Nigel!).

    That said, I tend to have the Volume hovering around "8", with the Treble between "7" & "9" and the Bass between "3" and "9" depending on how full I want it sounding (since the Bass control's sweep is very wide and subtle).

    So, besides making the chassis, the changes I made to my Champion 600 are doable for anybody with basic skills working with electronics - just be safe and take precautions to avoid getting electrocuted!

    Otherwise, if you already have a Champion 600 (and maybe an external speaker cabinet), making the amp into an affordable "head" version of sorts is certainly within most people's grasp; New tubes, a couple 250k audio pots and Nigel Briggs' noise reducing upgrades are all that you really need.

    Anyway, I'm so glad I decided to keep my Champion 600 (in its now totally unrecognizable mutated Frankenstein form) and I really hope this helps to inspire others who may also wish to butcher, I mean, improve theirs...

    Good Luck!

    Last edited: Apr 20, 2018
    ecosse, Tsquared, FRESHMEAT and 3 others like this.
  2. Mike Eskimo

    Mike Eskimo Telefied Ad Free Member

    Nov 9, 2008
    Nice job ! Never dug those 600's in the store. Cool you made something great out of it.
    AxemanVR likes this.
  3. AxemanVR

    AxemanVR Tele-Afflicted Ad Free Member

    Dec 27, 2011
    Minnesota USA
    I decided to include the following information in case someone wants to attempt some of these mods on their Champion 600...

    Here are the circuit changes and a simple diagram outlining the tone pot additions:

    02 Pot Wiring.jpg

    FYI: There is one very useful tip I have for anyone wanting to do this...

    I wasted a lot of time trying to desolder the old resistors in order to remove them from the PCB, but this just ended up wrecking some of the circuit traces and I had to add a jumper wire in one spot to bypass that short in the circuit:

    03 Point to Point wiring.JPG

    If I were to do this over again I would just cut the resistors off - leaving as much of the resistor's lead wires attached to the board as possible. This way you can effectively use these lead stubs as "wiring posts" that you can solder your tone pot wires to. Live and learn, right?

    I got the pots from this retailer:

    250K D-Shaft Pots A.JPG

    And these smaller 7/8" Fender "D-Shaft" Princeton 65 knobs fit both the pots above as well as the stock pot on the original Champion 600:

    Princeton Knobs - eBay.JPG

    It's for a Princeton 65 amp (as well as others I'm sure) - Fender part number 0054419049 - and (FYI) it slid onto the Champion 600 volume pot perfectly.

    pot knob.JPG

    Anyway, here are some picts of Nigel Briggs' noise reduction mods:

    09 Nigel Mods.jpg

    I didn't provide specific information on these noise reduction mods since I didn't want to undermine all the hard work Nigel Briggs did to make his mod kit work, but last time I checked Nigel still sells them on eBay; Just look for his product line there under "Alnicomagnet Mod" (

    The following kit includes all the stuff I installed as well as a "pentode/triode" switching circuit (output power reducer) which I chose not to use:

    Alnicomagnet Mod Kit AA764 Champion 600 Gretsch G5222

    He also has another kit that only provides the noise reduction components and does not include the HT fuse, standby switch or pentode/triode parts, so it's a little cheaper:

    Alnicomagnet "Basic" Mod Kit Champion 600 Gretsch G5222 tube valve amp

    P.S. Nigel doesn't pay me to promote his products - although he should! ;)

    Hope this helps and Good Luck!

    Last edited: Apr 21, 2018
  4. AxemanVR

    AxemanVR Tele-Afflicted Ad Free Member

    Dec 27, 2011
    Minnesota USA
    Some more "fine tuning" upgrades to report!

    What started off as just a short "blurb" quickly wound up being a rather long-winded expose', so I decided to separate this into three distinct sections:

    1) New Speaker
    2) New (Old) Power Tube
    3) New Effects Pedal

    I'll start off with the improved speaker I recently discovered...

    Okay, so, while I've been loving how great my ChampTone sounds there still seemed to be something else that was needed, something that was just a hair off from being perfect, so I experimented with a plugging the ChampTone's amp section into my other speaker cabinets to see how they would sound (something I hadn't done since I added the Treble and Bass pots).

    The first one I tried was my Mesa Boogie cabinet with a single 8-ohm 12" MC-90 Celestion "Black Shadow" speaker:

    B01 Mesa Cab.jpg

    Then I ran it through a vintage 1963 Gibson "Invader" GA-30RVT amp that I converted into a speaker cabinet. This one is loaded with a pair of 16-ohm Jensen speakers (a 12" C12Q and a 10" C10Q) that are wired in parallel, also for 8-ohm use:

    B02 Gibson Cab.jpg

    While each of these external cabs has their own unique voice, neither of them really jumped out as a major improvement - BUT! - then I ran them both together and - BAM! - the sonic deliciousness nearly ripped my stupid ugly head off!!!

    B03 Mesa+Gibson Cabs.jpg

    It's a little difficult to explain, other than to say that there was not only a noticeable jump in sweetness, tightness, warmth and clarity, but that "boxy" feel I described earlier had all but disappeared. I originally thought this boxiness was located higher in the treble range, but now I'm really thinking it was more in the midrange, causing the tone to lack a bit of openness. Either way I started to notice it more after comparing the two setups, and now there is no question that the internal speaker suddenly sounded much less appealing.

    So, does this mean the Eminence "Especially Designed for Fender" speaker sucks?

    Well I did some more testing and, if I had to make an educated guess, I'd say an impedance mismatch may have been a more likely culprit than the speaker itself...

    You see, this amp has a 4-ohm speaker output but I've been using 8-ohm speakers in it. This impedance mismatch is usually considered to be safe and most of my research seems to suggest that any resulting tonal changes would be minimal, but, I'm also pretty sure that the people providing their observations were mostly using amps with the more common two or four (Class A/B) tube complement, while mine is obviously of a single ended Class-A design, which may be more sensitive to such changes.

    I'm no expert here but after going back and forth between the the 4-ohm "to die for" setup and a variety of other speakers (all having 8-ohm loads) which exhibited similar (i.e.; less desirable) characteristics, it was clear to me that a matching speaker load was at least something worth keeping in mind moving forward.

    Anyway, going with these assumptions I decided to start looking for a 4-ohm replacement speaker and after doing a lot of searching I discovered two things:

    A) There are tons of 12" speakers that appear to fit the tone I was looking for,


    B) Most of them are either 8 or 16 ohm!


    So I was fairly limited in my choices, but I still managed to find something that seems to hold much promise for getting what I need.

    Before I go on I just want to be clear that this is in no way an "endorsement" for any specific brand or model, but after a fairly exhaustive search I finally decided to try the Eminence "Texas Heat" speaker:

    B04 Texas Heat Installed.JPG

    Time to fire it up and hear how sounds!

    Well, keeping in mind that this was a brand new speaker when I installed it and hasn't been broken in yet, I'm happy to announce that my initial impressions were very good.

    Not surprisingly it did feel a little "stiff" at the beginning and I had to do some tweaking on the amp to find its new sweet spot. Some of the initial stiffness seems to center around a slightly pronounced midrange, but since I don't have a midrange control I had to make due with adjusting just the VOLUME, TREBLE and BASS controls - and that's where I discovered something very interesting...

    If you recall, I mentioned earlier that the BASS pot has an extremely subtle range of adjustment. Well, even though the Texas Heat seems to have plenty of bass I noticed that turning UP the BASS control, which only slightly increased the lower frequencies, seems to subdue the midrange a bit too. So after cranking the BASS up - along with the TREBLE to keep things tight - the Midrange became much more balanced in the mix.

    In addition I also stumbled upon a couple other surprising "phenomenons" as they pertain to the ChampTone's two inputs (1 & 2) and VOLUME control...

    B07 Low Input.JPG

    After switching between the amp's two inputs I discovered that the #2 (low) input seemed to sound better than the #1 (high) input now - which was the other way around before. All I can say is that the #1 input sounds a bit more "brash" compared to the #2 input (for lack of a better word). Not horribly so, but still a little less pleasant. After analyzing the C600 circuit, it's clear that the #1 input's signal no doubt slams the preamp tube a little harder than the #2 input, so it could be overloading things just enough to make it sound ragged. Either way, the #2 input just sounds smoother and more "vintage", which is exactly what I'm going for in this amp.

    Note: Due to the expected drop in volume while using the #2 input, the #1 input can still be used if the extra output is really needed, and in most "live performance" situations the difference in sound quality probably wouldn't be all that noticeable anyway, but for how I'm currently using it for small venue and recording purposes, the somewhat lower output is really not an issue.

    Anyway, besides all that, there is also an interesting "Volume/Treble roll-off Phenomenon" that has become apparent...

    In a nutshell I basically noticed a significant treble roll-off as I turned down the VOLUME control. For guitars like my 2003 Fender '52 AVRI Telecaster, which is harmonically rich and thick, this causes the high end frequencies to sound a little dull and lifeless, so I just leave the VOLUME on "10" for this guitar. Brighter guitars are more forgiving, but after a certain point you can only go so far before an unacceptable level of treble loss becomes intolerable (I do have a nice fix for this though, outlined below in the "Effect" section).

    Once I realized these factors it became obvious that my output level options were now a little more limited, but that may change once the speaker breaks in over time.

    Otherwise, I'm very pleased with what the Texas Heat has to offer...

    I've only managed to really push it a handful of times but it already seems to have loosened up a bit and there is plenty of sparkly chimey goodness to go around when dialed in correctly.

    The highs in particular are round and smooth while still retaining that all-important clarity and shimmer. Even while hitting the strings hard the highs never became unusually harsh or unpleasant. In fact I had to really try to get a piercing treble tone from this speaker, so needless to say I'm really impressed with this aspect of the sound I'm getting from it.

    The bass is also adequately tight, yet full sounding. I was getting a tighter bass with the 4 ohm dual-external speaker setup I used before, but I'm still happy with the response I'm getting now, which hopefully won't loosen up too much when broken in.

    The mids are a little stiff - but not a deal breaker - and they will hopefully loosen up as time goes on.

    There are also two different sides to this amp, soundwise, and that is the ever so ubiquitous "Clean vs. Dirty" aspect to it.

    The Clean side is what I've been mostly discussing so far here, but when pushed this speaker also shines and, while I feel like the clean-to-mildly-pushed sounds are the best fit for this particular amp (on its own), with the Texas heat the overdrive tones are greatly improved.

    That said, I still think an overdrive pedal is needed to really push this amp into the "brown" crunch zone and with my Tubescreamer type pedal I can really get an awesome singing sustain out of the ChampTone, although beyond that I feel my humbucker guitars are better suited to really make it scream.

    What's important here is that this little firecracker can convincingly pull it off when correctly set up to do so and I plan to do a more thorough review on the heavier sounds when I get the chance...

    2) TUBE

    Besides the speaker change I also managed to find this little gem:

    C01 RCA 6V6.JPG

    It's actually one of two vintage RCA 6V6GT "Gray Glass" power tubes I recently got off eBay for $10 each! I'm not sure why, but these tubes aren't selling for the huge price that other vintage tubes are, but I'm not going to question it either. Both sounded really nice, but one stood out as slightly better so I'm currently using that one in the ChampTone right now.

    But, did it make a HUGE difference in tone?

    Well, in a word "No", but it did add a "sprinkle" of sweetness overall (in my opinion) and will hopefully last a long time - of course you never know with these older tubes.

    Speaking of "sweetness"...

    3) EFFECT

    There is one last thing I'd like to mention, and that is the addition of my Voodoo Lab "Sparkle Drive Mod" pedal:


    As I mentioned a short while ago, when I turned the ChampTone's VOLUME down there was a noticeable drop in the higher frequencies. Since I want to be able to turn it down without the tone suffering I decided to look for something to replenish the "sparkle" so to speak, so the Voodoo Lab's Sparkle Drive Mod seemed to be the ticket.

    Okay, so the VLSDM is best known for its overdrive tones, but that's not why I got it. What I wanted was something to subtly reinvigorate the harmonic content without being too obvious.

    I actually got the idea while listening Jerry Garcia's solo on "Touch Of Grey". His tone here is deceptively clean yet has a bit of "hair" to it... just a tinge of juicy "something" hovering over everything, and that's what I wanted!

    So, after eliminating EQ's, compressors and sonic maximizers, I decided that some sort of transparent overdrive must be the ticket and the Sparkle Drive Mod's features in particular caught my attention; especially the CLEAN control, which allows you to balance how much of the overdrive affects the original signal.

    Well, all I can say is that it worked!

    If you look at the settings I use on mine (in the above picture) you'll noticed the I have it on MOD setting #2 with the GAIN set fairly high but the CLEAN set even higher, thus dialing in just a hint of the effect. The TONE knob dials in the extra treble I needed and the VOLUME is set at unity gain (the output level is the same as when the unit is bypassed).

    Like I said, it works great and now I can lower the VOLUME on the ChampTone a bit and still get a lively, sparkly tone!

    The nice part is that I'm not entirely dependent on the Sparkle Drive to get a great tone from my amp, but it sure is nice to know it's there in case I need it as well. But, truth be told, ever since I got it I pretty much have the Sparkle Drive on all the time - it's that good (for how I'm using it anyways).

    In conclusion...

    I really don't know how I can possibly make my little ChampTone sound any better, short of major surgery, but if I come up with something I'll be sure to let you know!

    B06 ChampTone Test.JPG

    Good Luck!

    Last edited: May 17, 2018
    stevemc likes this.
  5. AxemanVR

    AxemanVR Tele-Afflicted Ad Free Member

    Dec 27, 2011
    Minnesota USA
    Time for yet another a little update...

    So I've been running the Eminence Texas Heat 12" speaker in my Fender AA764 based ChampTone project amp through its paces for several weeks now and have come to the following conclusions:

    a) I really think this speaker is awesome - when used with the right setup - but!...

    b) I really don't think it's the best fit for my ChampTone combo.

    There seems to be a bit of a tradeoff with it since (as you shall see) some of my statements appear to contradict themselves.

    For instance; I absolutely LOVE the smooth and warm highend texture of the Texas Heat, BUT was increasingly wishing it had a little more clarity, sparkle and bite.

    Also, as I mentioned previously, I was also hoping for a bit tighter bottom end - even though the bottom sounds delicious!

    So, by now you should be able to gather by my descriptions of the Eminence Texas Heat is that it's a great speaker (for taming an overly bright amp for instance), but decidedly not the best suited for my current application.

    The main problem is that the Champion 600 seems to be voiced to have a darker, fatter tone which tends to sound best with brighter guitars, such as my 2012 Fender American Standard Stratocaster, but gets a little muffled and boxy with anything that's already fat, like my 2003 Fender AVRI '52 Telecaster or my humbucker guitars. In fact I've always suspected that it was designed around the Strat more than anything else.

    Not surprisingly I'm pretty much forced to set the ChampTone's Treble control to "10" even with the Strat, which doesn't leave much room for flexibility as you can well imagine.

    I guess I could just make it my "Strat Amp" but after plugging the ChampTone into one of my other external speakers (as described earlier) and hearing how open and airy it can be with just about any of my other guitars, I decided I wanted more versatility out of it.

    The good news is that I'm still confident that it's not the amp itself causing the issue and I remain convinced that the Fender Champion 600's circuit is a great take on a classic design that was unfortunately put in a mediocre package.

    Either way, the Texas Heat just doesn't seem be the "best fit" here and so I decided it was time to look at further options in this area... which of course meant once again searching for the perfect speaker and that always inevitably involves a lot of investigation along with the apprehension of potential disappointment that follows.

    After looking at several choices I started focusing mainly on Jensen's line of speakers, since they often seem to have a nice highend presence in my experience. After looking at the specs and reading reviews, the Jensen MOD 12-70 stuck out as something I'd be interested in... tight bottom end, smooth mids and bright highs all seem to be the outstanding traits. The sensitivity (efficiency) is a little lower than the Texas Heat (96db vs 99db) so I may lose some perceived output, but if it's able to eliminate some of that boxiness then the tradeoff would be well worth it. My only hesitation was the name "Mod" (for "Modern") which was not exactly the type of sound I was going for, but luckily that ended up being a sales pitch more than anything, as you shall soon find out...

    I should also add that I am talking about the 4-ohm version of the MOD 12-70, so keep that in mind as you evaluate my observations...

    Anyway, I currently have a Jensen C12Q speaker installed in one of my external speaker cabs which is also on the brighter side but also has quite a noticeable midrange bump I'm trying to avoid so, after going back and forth a bit, I decided to pull the trigger and gave the Jensen MOD 12-70 a try.


    Well... so far so good!


    First of all, the Jensen MOD 12-70 is noticeably brighter and clearer out of the box than the other speakers I previously installed in the ChampTone and I was instantly relieved that the highend cobwebs had completely disappeared!

    The bass has also tightened up considerably but at the slight cost of some lower-end warmth and fullness (so slight in fact I probably shouldn't have actually even mentioned it). I'm quite hopeful that this will only improve as the speaker breaks in. Besides, due to the abundant brightness I can now dial back the amp's treble control enough to even things out more, so I'm not the least bit concerned either way.


    The Midrange does have that characteristic Jensen bump, but in a less "in your face" way compared the C12Q and the MOD 12-70 provides just enough pleasant twange to the edge of the sound to add some much welcomed sweetness without overly "coloring it" any more than necessary.

    So the main tradeoff here is the extremely minimal loss of some bottom-end girth but, when you account for the crisp clear ringing top-end and rich juicy midrange now, it is SO worth it!

    As and added bonus, I no longer need any external effects to get this amp into the "to-die-for" zone anymore and have been mainly plugging straight in these days with nary a hint of wanting to add much of anything into the mix. Don't get me wrong, I'll eventually throw in things like reverb, delay or chorus at some point, but for now I am more than content to hear the sweet pure tone coming out of it now. It's heavenly!

    Something else I also noticed was how early it breaks up when pushed. I can lightly pick or strum a sweet clean tone one second, then bash the strings for some immediate crunch the next! I was actually quite surprised to discover how easily the two sounds can be coaxed back and forth and, while it's still a bit too early to tell, I think I really like it!

    Of course this most likely indicates a certain loss of clean headroom, so that may not suit some people's needs, but for me it was a rather exciting discovery since I like my cleans to still have a little grit.

    Anyway, I'm going to be pushing it pretty hard for a few weeks to break it in and then report back with the results at that time, but for now I'm having a really good feeling about the Jensen MOD 12-70 and (cross your fingers) I'm feeling 99.999% positive that I have finally found the missing piece to this crazy sonic puzzle!



    Last edited: Jul 10, 2018
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