Increase / decrease output pot on a tonebender mkii

[chromesphere]

YO!
I looked around couldnt find a direct answer, im sure this is an easy question though.

I built a tonebender mkii from fuzzcentrals schematic (the first one in the list): http://fuzzcentral.ssguitar.com/mkII.php

I didnt ahve a 100ka pot, so i used a 10ka pot.  The level control still works perfectly fine, but it got me thinking.  Would increasing the pot value add more volume, or take it away?

Heres the mental process (if you can call it that) that im up to at the moment.  When the pots turned completely down, the output is basically sitting at ground so theres obviously nothing coming out of the output. 

When the pot is turned the other way, you get all the voltage available.  So does increasing the pot value make more voltage available or less, i guess could be my question?  And the answer, i think, is more...

Did i just answer my own question or am i totally wrong?

Thanks for your help. :-)
Paul

[LucifersTrip]

I didnt ahve a 100ka pot, so i used a 10ka pot.  The level control still works perfectly fine, but it got me thinking.  Would increasing the pot value add more volume, or take it away?

decreasing the pot will decrease volume and make it more trebly. it is a very common mod for the Fuzz Face to use a 250K vol pot instead of 500K to make it less muddy. In that case, there is only a small vol decrease. if you lower it to 100K, you'll notice a big vol drop and large treble increase.

It's probably similar in the MKII since Q2/3 are basically the same except for the biasing.

Do an experiment. Use a 500K pot and put a second 500K pot across that pot (so you basically have a 250K with a different sweep). Slowly lower the second pot and listen as the volume decreases and treble increases.

That is what this "cheezy" tone control does...
http://fuzzcentral.ssguitar.com/schematics/ashfuzzschem.gif
The 1.8K is there so the vol does not get too low and the tone too trebly

[chromesphere]

Thanks for the info lucifer, its funny you say that because i did notice a huge amount of top end and was wondering why it sounded that way. I'll get a 250k pot and try and see the difference. 

So there you go, i was miles off.  Not much difference in volume, but a huge difference in tone

Paul

[nocentelli]

The REASON you get more bass roll-off with a smaller pot is the high-pass RC filter that is made by the output cap and volume pot lug 3->ground resistance: Even at maximum volume, the output end of the cap still sees a resistance to ground: in your case, only 10k. This determines the cut-off frequency of the HP filter: increasing either cap or pot value will lower the cut-off frequency and allow more bass frequencies to pass. So, if you don't have an appropriate value volume pot, you can use a smaller pot, but will need to increase the cap value to compensate - There are loads of references to "RC filters" online, and even a few online calculators.

[chromesphere]

Thanks for the explaination nocentelli.  I was looking at that cap thinking that it was probably forming an RC filter (after lucifer explained to increase the pot value), thanks for confirming that!

Edit: I thought i would plug those values into the high pass filter calculator over at muzique.com and see what was going on.  WIth the correct values, 100k pot and 10nf i got 159.2hz and for the 10k pot (and 10nf cap) i get 1592hz!  No wonder there was no bass! That explains it

Paul