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Champ Micro mods

Discussion in 'Shock Brother's DIY Amps' started by Hyakuya, Apr 15, 2021.

  1. Hyakuya

    Hyakuya TDPRI Member

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    Hello....

    In the spirit of 'if it ain't broke pull it apart and change it' I feel the need to try some mods on my Champ Micro starting with the 3 way negative feedback switch.

    I already have the on-off switch for NFB so it's a simple job to replace that with a SPDT switch and add a resistor but I wanted to ask what size resistor should I use.

    upload_2021-4-15_9-1-44.png

    The switch will give me Normal / None / Heavy and I have the 10K Normal feedback resistor in place (I'm using the 8 Ohm tap on the OT).

    I'm thinking I should be around 30K for the new resistor setup like this....

    upload_2021-4-15_10-0-39.png
     
    Last edited: Apr 15, 2021
    robrob likes this.
  2. robrob

    robrob Poster Extraordinaire Ad Free Member

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    You can alligator clip in a 50k pot to find the NFB resistance value you like.
     
  3. Hyakuya

    Hyakuya TDPRI Member

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    What about soldering in a 50k pot instead of a resistor and having the option to adjust the heavy NFB resistance whenever I want.....
     
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  4. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Put a 10k in line with the pot to keep from going too low in NFB resistance and you're golden.
     
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  5. Hyakuya

    Hyakuya TDPRI Member

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    Had a fiddle today...

    First job was to reduce the size of the V1 cathode bypass cap from 25uF down to 1uF. This has done a lovely job to brighten the humbucker so winner winner chicken dinner for that mod.

    3 way NFB has also gone in so I have off and normal through a 10k resistor as before but I've added a 50k pot as a third option on a new SPDT switch. The pot is wired across the 2 outside contacts of the switch so it still uses the 10k resistor as recommended.

    I've set the pot to 20k for now so I get 30k overall but I'll have a play and see what different resistance values gives me.

    Right... back to the Amp Mods page on Robs website to see what's next.

    You know where this is going don't you...building another amp isn't it !!
     
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