# Blue Breaker - 'Presence' switch



## Alchemy Audio (Mar 7, 2019)

I wanted to add a two position 'presence' switch to the build. Am I right that I should install this in place of the 10n C8 position?


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## zgrav (Mar 7, 2019)

maybe the C6 cap would be better, since the r/c combination there sets the frequency for the tone control.  I think you would use a dpdt switch to select between two different capacitors at that point.      You could change c8 to change the high frequency rolloff, but that is not quite the same thing.  Or you could try both and see which you prefer.


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## Alchemy Audio (Mar 7, 2019)

Thanks! Worked like a charm.


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## zgrav (Mar 7, 2019)

Great!  What other value did you pick for the cap?


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## Alchemy Audio (Mar 7, 2019)

I was playing around with a few. I think we went with .22uF but I may change it.


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## phi1 (Mar 7, 2019)

The KoT / Wampler Pantheon style presence control is a pot in series w c8.  So you could switch in resistor there for higher presence.  Or, subbing c8 for a different value would change the cutoff freq of that filter, adding a resistor in series keeps the frequency the same but adjusts the slope that it rolls off, as I understand it.  

Or subbing c6 works, but note that your tone pot is already adjusting the cutoff freq of that filter, so the tone pot and switch would be very interactive, whereas c8 is a separate filter.

In either spot 0.22uF seems pretty drastic considering the math, but then again the ears have the final say...


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