# Replace A500k with B500k with in a tube screamer?



## RealLyfeGangsta (Apr 1, 2022)

Hey guys,

I want to build a tube screamer and I have all the parts I need on hand except for the A500K pot. I have a B500K and I also have an A100K pot to spare. Could I replace it with the B500K like in the drawing, or could I alternatively make some changes in the circuit to use an A100K instead? Where I live, shipping is very expensive, so that's more or less out of the question for just one part.


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## jesuscrisp (Apr 1, 2022)

Yes you can but the gain control sweep will be different, as you get more distortion earlier in the turn. But overall gain amount will be the same.


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## RealLyfeGangsta (Apr 1, 2022)

jesuscrisp said:


> Yes you can but the gain control sweep will be different, as you get more distortion earlier in the turn. But overall gain amount will be the same.


Alright, thank you!


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## Bio77 (Apr 1, 2022)

The picture you made is your best bet.  Make the 500A out of the 500B.  I'd use the 100k resistor (1/5 the value). I'm not sure you have the resistor between the right pot legs, you should double check.  Seems like you've read this but just in case here is a link for the  pot conversion:



			The Secret Life of Pots


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## RealLyfeGangsta (Apr 1, 2022)

Bio77 said:


> The picture you made is your best bet.  Make the 500A out of the 500B.  I'd use the 100k resistor (1/5 the value). I'm not sure you have the resistor between the right pot legs, you should double check.  Seems like you've read this but just in case here is a link for the  pot conversion:
> 
> 
> 
> The Secret Life of Pots


I haven't read it and thanks a lot for the info and the input!


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## Bio77 (Apr 1, 2022)

RealLyfeGangsta said:


> I haven't read it and thanks a lot for the info and the input!


Oh cool, this article was a game changer for me.  You can make a C or A taper pot out of any B most of the time, depending on the circuit.  Also, its pretty easy to add a resistor between the legs of a pot without tearing the pedal apart, if you ever need to adjust the taper in a finished build.


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## cdwillis (Apr 2, 2022)

This is just my two cents. RG Keen is an electronics genius, but I would order the a500k pot along with more parts for more builds so it's worth the shipping. That's assuming you're going to build some more pedals.


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## giovanni (Apr 2, 2022)

cdwillis said:


> This is just my two cents. RG Keen is an electronics genius, but I would order the a500k pot along with more parts for more builds so it's worth the shipping. That's assuming you're going to build some more pedals.


+1 to that. If I’m missing a part it’s just an excuse to make a new order for MOAR pedal builds!


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## zgrav (Apr 2, 2022)

In the meantime, use the B500K pot.  As noted you get the full range of sound intended with the pedal, just a different amount of change at different parts of the rotation.  Experiment with adding another resistor between the legs of the pot if you want to try different options.


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