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Details about  Alnicomagnet "Blues Harp" Mod Kit Champion 600 Gretsch G5222

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Alnicomagnet "Blues Harp" Mod Kit Champion 600 Gretsch G5222
Item Ended
26 Oct, 2015 22:49:52 GMT
£5.00 Royal Mail International Standard (Small Packets) | See details
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Item location:
Rochdale Lancashire, United Kingdom


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Last updated on  29 Jun, 2015 15:31:17 BST  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
Returns Accepted: Returns Accepted Brand: alnicomagnet
MPN: Does not apply Model: 600 Blues Harp
EAN: Does not apply


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Hi and welcome to my listing for this brand new Alnicomagnet "Blues Harp" mod kit for the Fender Champion 600/Gretsch G5222 valve combo.

This kit is suitable for all territories and mains voltages.

I've been asked so many times to come up with a decent sounding mod kit specifically for Harp players, so, after many many hours of research and development, tweaking and listening, here is the result.

I've taken my Champ 5F1 voiced Champion 600 as a base design and tweaked the circuit in a number of very important areas. Specifically, I have looked at, and addressed, plate voltages on the preamp tube, tube type, preamp bias, negative feedback, and coupling capacitors.

The results are as you would expect: beautifully progressive and warm sounding preamp breakup, balanced with a progressive and thick output valve breakup, easily controllable with just the single volume control, together with a thick deep ballsy voicing for that authentic "Chicago Blues" sound. The difference between the stock amp and this mod kit is quite astonishing.

Please note that this mod kit voices the amplifier specifically for Harp use. (It is no longer suitable for electric guitar, although playing a guitar through it is quite interesting, if a little "strange").

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.

Check out Mat Walklate playing various harmonicas through three different microphones.

This kit replaces the normal stock preamp. It uses the design of the earlier Tweed Champ 5F1, but goes a step further to give an authentic "Chicago Blues" sound suitable for Blues Harp, (hence the name). Not suitable for electric guitar! This dispenses with the tone stack completely, along with some other important changes. This gives a much thicker sound with a nice early valve breakup.

Instructions and pictures are kept in a folder. The folder is stored on a download site ( 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 (

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.

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!


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


On 26-Feb-09 at 14:47:36 GMT, seller added the following information:


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

Here's an email and some 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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