Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Kesi from Hungary on May 29, 2022, 01:27:38 pm

Title: Fender champ 12 Effectrode mod
Post by: Kesi from Hungary on May 29, 2022, 01:27:38 pm
Hello, does anyone have experience with the Effectrode mod on a Fender champ 12. I'm working on the mod and finished the first part of the gain channel.  Now the clean part.  In the diagram of Effectrode a new/extra 220K resistor is drawn with a line just above resistor R21.  I don't know where to put it.  Instead of jumper W 5?  Or something else?  I'll try to post a picture and schematic.https://el34world.com/Forum/Themes/default/images/post/xx.gif
Title: Re: Fender champ 12 Effectrode mod
Post by: PRR on May 29, 2022, 01:44:44 pm
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Title: Re: Fender champ 12 Effectrode mod
Post by: Kesi from Hungary on May 29, 2022, 01:51:50 pm
very fast answer.

You mean parallel? Thats makes it 440k.
Title: Re: Fender champ 12 Effectrode mod
Post by: sluckey on May 29, 2022, 02:09:47 pm
very fast answer.

You mean parallel? Thats makes it 440k.
No. Replace R21 with a jumper wire. Replace R16 (47K) with a 220K. You could just use the removed 220K rather than using a new one, that is if you don't booger up the original 220K.
Title: Re: Fender champ 12 Effectrode mod
Post by: Kesi from Hungary on May 29, 2022, 11:14:38 pm
Thanks for solving the problem.  This week the last parts will arrive and then I can finish the project.  Regards Kesi
Title: Re: Fender champ 12 Effectrode mod
Post by: pietrocop on February 04, 2026, 07:51:10 am
Thanks for solving the problem.  This week the last parts will arrive and then I can finish the project.  Regards Kesi

Hi, have you completed the modification? I did it myself recently and had the same doubt as you. I followed the suggested approach (removed R21 and connected without a resistor), but I don’t like the overall result. The Overdrive channel has improved, but the channel’s volume has increased a lot and it already distorts at 1. How are you finding the modification?
Title: Re: Fender champ 12 Effectrode mod
Post by: Kesi from Hungary on February 05, 2026, 05:45:52 am
"Hi, I wasn’t satisfied with the mod or the other variants I tried either. And that’s exactly the problem with this amp. You either love it or you don’t, but with this amplifier it’s really hard to have both a good clean channel and a good dirt channel."