Tonepad's MXR Blue Box mod help

[stompvulture]

Hello everyone-

Brand new to the forum, but not to DIY building. It'll be 10 years for me this year.

I have a question of the tone mod at Tonepad. For the life of me I can't figure out from the build feedback page where to place the 10k pot it in the PC. One thread was to tie in the 1st and 3rd lug between C9 and C10 and the 2nd to the volume? nothing. Is it the caps I'm tying into, the juncture, what volume lug, I tried different combos, but not getting anything. If anyone can add some clarity to this it would be greatly appreciated. Going on ten years of doing this and I still get thrown for a loop.

BTW, I did do a search here on the Blue Box, and the info on it is amazing. I would like to try Mark Hammer's post of switching out the .1uf cap with a 2200pf, maybe with a DPDT? Oh yeah fanstastic pedal , just would like some tweaking range.

Thanks in advance.

[Mark Hammer]

Q: Do you want to be able to adjust the overall tone of the two blended signals, or the octave-down alone?

That will determine the locus of the mod.  I can see some virtue in each approach.

[stompvulture]

I was thinking of the overall tone. But had not considered the 2 octave approach. Whats your thoughts on these?

[stompvulture]

Update Mark. I added a DPDT with a 2200pf to flip out the .01uf for added treble and works great. I also attempted to add a 50k pot in parallel with R20 and didn't get any results, maybe because of the treble bleed switch. I also have an octave switch mod as well.

[Mark Hammer]

R20 in the drawing I'm looking at is the Blend pot.  Don't know that a parallel pot would do much of any use there.

If you wanted to introduce treble rolloff specific to the octave down, you'd have a cap to ground from the junction of R17/R19.  For my money, a 3-position SPDT toggle (center-off) with no rolloff, or one of two different rolloffs will probably take care of it.  A .015uf cap gets you a rolloff starting around 190hz, and 8n2 gets you a rolloff just under 350hz.

[stompvulture]

Thanks Mark-

I dig the caps on the SPDT. I'll play around with some other variants there to see what I get.