where is small stone mods

[dj_death]

I can't find the file with Mark Hammer's mods on Small Stone i have this
dead link : http://hammer.ampage.org/files/SS_Phasefilter_mod.gif . I don't understand really this phase filter mod. Does anybody have these
mods?

[moosapotamus]

Refer to the Tonepad project...

Lift the end of C9 where it goes to IC3 pin 6, and tie it to one of the center lugs on a DPDT toggle switch.

Lift the end of C8 where it goes to IC4 pin 6, and tie it to the other center lug on that same switch.

Wire two of the poles on one side of the switch back to the pads that you lifted the ends of the caps from on the PCB. This will be the 'stock' setting, with the last two stages configured normally, as all-pass filters.

Wire the other two poles on the other side of the switch to ground. This will be the 'phase-filter' setting, with the last two stages configured as low-pass filters.

In addition, you'll want to do the 'vibrato' mod, which cuts the straight signal from the output. This will give you the full phase-filter effect. Lift the end of R8 (30K) that ties to C7/R13 and tie it to one of the lugs on a SPST switch. Tie the other lug on the switch back to the pad that you lifted the end of the resistor from on the PCB.

I belive that's it. YMMV

~ Charlie

[Mark Hammer]

I think I may have screwed up the illustration of what traces to cut, etc., and pulled the picture without having replaced it.

As Charlie correctly points out, though, the cap that has one end tied to the junction between the OTA and the Darlington pair (which would be pin 10/12 and 5/7 on a 13600 is you are modding a Ross/Ropez, pin 5 on a 3094 if modding a stock Small Stone, and pin 6 on a 3080 if modding a Piedrita from Tonepad) is the one to relocate. The end tied to these pins stays where it is, and the other end of the same cap that connects up to the input gets moved to ground.  When the cap is tied to the input it forms an allpass filter.  When it is tied to ground, it forms a lowpass filter.

In theory, it doesn't really matter which stages are configured as lowpass and which as allpass, however my preference is to make only the last two stages lowpass.  This may make a difference with greater amounts of resonance.  You can also make all 4 stages lowpass but it is the combination of low and allpass that provides the slinky blend of tremolo, vibrato, and wah that this thing does so nicely, so aim for 2+2.

As Charlie also correctly points out, the phasefilter mod works best when there is no dry/straight signal in the mix.  That way you get to hear the effect of the lowpass filter being swept, whereas with dry signal in the mix, high end keeps being present, thinning out the impact of the owpass.  For a further explanation of this effect, go to my site (http://hammer.ampage.org), scroll down a few pages, and look at the review of the Blacet Phasefilter in one of the back issues of DEVICE.  If memory serves, it is somewhere around issue 4 or so.

[dj_death]

Thank you Charlie and Mark for your detailed description of the phase filter mod. I built the tonepad pcb layoutand i plan to mod small stone as Charlie did in his frankenstone pedal with "on off on" spdt switches for all 4 stages. I guess i'll do the procedure Charlie described in all the stages. I'll try the vibrato mod too. Thank's again guys.