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Details about  Alnicomagnet Mod Kit AA764 Champion 600 Gretsch G5222

Alnicomagnet Mod Kit AA764 Champion 600 Gretsch G5222

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Item location:
Rochdale, Lancashire, United Kingdom
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Last updated on  18 Feb, 2015 15:47:27 GMT  View all revisions
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Item specifics

New: A brand-new, unused, unopened and undamaged item in original retail packaging (where packaging is ... Read moreabout the condition
Type: mod kit
Model: 600 AA764 Brand: Alnicomagnet


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Hi and welcome to my listing for this mod kit for the Fender Champion 600 and Gretsch G5222 valve combos.

This kit is suitable for all territories and mains voltages.

For those who don't know, the Fender Champion 600/Gretsch G5222 is a 5 watt, all tube combo using a 6" speaker, wrapped up in a vintage style, late 40's early 50's cabinet.

Great, so what's the problem?

Well firstly, Fender/Gretsch ship amps to the UK with 230V mains transformers.

We in the UK however operate at 240V, always have, always will. Forget about EU harmonisation rules trying to simplify power ratings and the like. This is for the benefit of white goods manufacturers, not valve amp tone junkies like you and me.

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Yes, but surely 10 volts won't make that much difference?

Well, modern valve amp designers tend to design amps that operate on the limit.

A modern 6V6GT valve (such as a JJ) has an absolute maximum anode dissipation of 14 watts. Vintage 6V6 valves used to be rated at 12 watts.

I stripped the amp down and measured all the voltages and anode current and calculated the anode dissipation at 15.69 watts! This will result in a shortened valve life. What's more, there's no Standby Switch, meaning that when the amp is switched on from cold, the 6V6GT valve gets zapped by a whopping 416V until it warms up and starts to conduct. This initial shock tears and rips off the special coating on the cathode, causing "cathode stripping". Again, reducing valve life. This sudden high voltage also attacks the coupling capacitors, and tone stack network. (This is why coupling capacitors have such high voltage ratings). However, Fender use capacitors rated at only 400V, leading to possible future failure. The original Champs had nice valve rectifiers which have an inherent "soft start" meaning that they are much easier on the amplifier. That's why you could get away with not fitting a standby switch. Unfortunately, these new Champion 600 amps use silicon rectifier diodes which conduct almost instantaneously.

I managed to get hold of a Fender Champion 600 circuit diagram and sure enough, Fender specify a B+ voltage of 366V. My measurement read 381V.

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So, time to sort this out and get it back to spec.

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Next problem - hum and noise. Watch the video and compare the background noise levels. Investigations revealed three distinctly separate causes of the hum and noise. More work for me but I managed to sort it out.

As for what it actually sounds like, no problems here. Fender have used (with some minor component changes) an AA764 circuit, more commonly known as the "Blackface Champ" of 1964.

Ah but! I hear you cry, the blackface Champ had a volume, a bass, and a treble control. Well the Champion 600 also does in effect. It uses a "tone stack" network that gives a preset treble and bass setting. This circuit gives a great Fender clean sound, good for chord work. The network has a high insertion loss. It does not boost the treble and bass frequencies as such, rather it attenuates the mid frequencies more than the treble and bass.

This kit retains the normal stock preamp. (The middle amp in my YouTube video). For clarity I have named it the "AA764".

I also list another kit which uses the design of the earlier Champ 5E1/5F1 preamp. This dispenses with the tone stack completely, along with some other important changes. This gives a much thicker sound, with higher gain. (The amp on the right in my YouTube video). For clarity I have named the other kit the "5E1/5F1"

Instructions and pictures are kept in a folder. The folder is stored on a download site (download.com) You will receive a download link via email which will be sent to you at the same time as you receive confirmation from eBay that the kit has been shipped. I will use your PayPal registered email address unless you inform me of an alternative preferred email address. If you don't receive the link, please check your spam filter/junk folder, or contact me directly (alnicomagnet@hotmail.co.uk).

You will need a pdf reader to access the instructions. You will need a picture viewer to view the pictures.

The kit also contains all the parts necessary to fully mod the amp, while keeping the normal preamp.

This kit is suitable for all territories and mains voltages.

Hi, Just getting some early comments/feedback through from modders, some of which I thought I might share with you:

Hi Nigel,
I did the mods today and am VERY impressed! Very clear instructions, detailed pics and well written thoughts on not just the 'hows', by 'whys' as well.
I chose to just do the 3 hum/buzz mods and added a separate 'standby' switch and it sounds great!
Was even impressed that the futzy/farty sound I had before seems to have been banished as well, I can crank it up now, let her rip and she still holds together... though I will be getting a 1x12 cab tomorrow to put her through the paces further.
Thanks again!

Hi Nigel,

Received the amp back last Thursday, and it's seen a little bit of action since then!


I'm very, very impressed with the mods... Great balance w/. the 5E1 - the voicing suits me perfectly, & I love the break-up / distortion with the added gain. (FYI - I've switched the valves to Brimar 6V6 cryo & Brimar 12AX7, which are top notch.) Noise / hum are no longer issues, which is excellent news for recording. The triode / pentode switch is very useful - 2w for recording / late night practice, 5w for jamming etc. 2w seems even warmer / thicker. Great, great tones all round! Nice to have a standby switch too - flicking to this during breaks the amp doesn't feel as though it's cooking after a few hours use...


I went into the studio on Monday, and played it through a 1x12 - WOW! I was really blown away by it. The Fender was up against an old 70's Orange Hustler & it held it's own with ease. Lovely crystal highs, and bags of bottom & mid power. Fantastic! Could easily gig with that set-up, so long as it's mic'd. (I'm now planning to get a 1x15 cab for future sessions...)


BTW - I've left some (very positive) comments on the Fender Forum Champion 600 thread.


Many, many thanks for great work!


Warm regards,


 Photobucket - Video and Image Hosting

Photobucket - Video and Image Hosting

Photobucket - Video and Image Hosting

This kit is also suitable for the Gretsch G5222. Check out this article: Gretsch G5222



On 26-Feb-09 at 14:40:31 GMT, seller added the following information:


Both my kits are suitable for the Fame Tube 5 combo.

Here's an email and pics I received from Michael Schroder:

Hallo Nigel,


Finally the amp is assembled and is working fine! The readings I've taken were nearly the same as in your description. B+ Voltage at R11 was 362 Volt DC, anode pin 3 had 354,5 Volt DC, cathode pin 8 had 20,2 Volt DC, so I had around 334 Volt true anode voltage.

Next reading showed 40,5 mA at the red output transformer wire and connector. Multiplied with the Volt reading is 13,527 W, that's pretty near 14 W as you wrote!

After I've plugged in my guitar there was a big increase in the sound than before. Great! Now, with the Jensen speaker and the new tubes from "Tube Amp Doctor" it sounds fantastically! I think, this is the Fender sound everybody is talking about. It can be very twangy when playing clean, farty with a bit more loudness and even crunchy if turned to 10.

I'd like to have another kit for my second amp! Please send the paypal invoice for the kit.


Greetings from Germany and hope to hear from you soon.




(Michael Schroder talking about his Fame Tube 5 amp)



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