more soon, hopefully.
26.8.14
6.8.14
EHX Small Stone Modding
just a quick writeup on my latest venture into modsville: the Small Stone.
on the wish-or-want-to-try-list:
- get the effect to be more subtle at the twist of a knob (aka mix),
- a depth control might be nice (as in: amplitude of phase sweep)
- fix volume drop when pedal is engaged.
i found some of the stuff i needed on the net, came across some stuff i didn't think i'd need but sounded interesting, and couldn't find info on the depth control.
so, here we go.
#1, the classic: univibing. swapping capacitors in the phasing stages to get the sound closer to a univibe. liked the effect, didn't care for the option of swapping each stage individually too much, so i ended up throwing in a 4PDT, moosapotamus-style.
#2, the mix.
i tried what a lot of people refer to as a 'depth' mod, which alters the ratio of the mixing resistors and throws in a pot for the occasion. it does go from clean to vibrato (don't really like it as a vibrato, but ok). problem with this is that as soon as you flip the Color switch, you send phased signal back to the input to create extra resonance - and while that's nice, it also means your clean signal is now no longer clean, rendering this approach to the depth/mix mod sort of useless. to me, that is.
i tried running the feedback path to the second phase stage (like the Ross Phaser), seeing how that would solve that issue, but i didn't like the sound as much. it's still a valid idea, i guess, if you're into that kind of sound.
now, i already modded another small stone with a buffer in front and a booster at the end to compensate for tone suck/volume drop, and i was going to redo that with this one.
so i figured i could lose the mixing stage of the original effect altogether, take the buffered signal as the clean end for a new mix control, and still have the extra resonance the color switch provides.
works beautifully, as it turns out. you do get a slight volume boost at both extremes (the phasing effect is in the middle of the rotation, and it's always going to cost you some volume - nature of the beast) but i don't really mind. not enough to want to fix it, anyway.
#3, speaking of that color switch:
i altered the resonance/feedback path slightly. took out that half of the color switch and basically replaced it with a pot. 500K sounds exactly the same as no feedback at all, 10K minimum stops it from squealing - and you get everything in between.
the second half of the color switch messes with the LFO, and alters both the depth (the LFO's amplitude) and the speed of the effect.
i swapped it out with a SPDT because it was easier to position than the original bulky russian 2PDT.
i put in an on/off/on switch because it was what i had lying around, but the difference between the off position and the regular mode is so subtle i wouldn't bother with it too much.
since i was still hoping to find a solution for the depth control, i thought about fixing it in the deepest (color 'on') mode and bringing it down afterwards, but it turns out it still sounds a little different. maybe it messes with the waveform (haven't scoped it), or it shifts the whole waveform up slightly, i don't know. anyway, decided to keep it, in spite of coming up with
#4, a way to control the LFO's amplitude.
i read up on OTA's a bit, and i learned they spit out current rather than voltage. what's more, they do so based on the difference in voltage between their two inputs, much like regular opamps. so i figured if i wanted to control the amount of current coming out, i might as well try to control that difference.
and yes, if you hook pin #2 to pin #3, rendering the difference 0, the lfo shuts down.
i went the crude way and hooked up a 100K pot between both inputs. at 100K, behaviour is the same as before. turning the resistance down, the amplitude drops and the phasing gets more shallow.
there is a certain point where the speed is affected as well, and the whole thing speeds up quite dramatically. i don't mind. it can probably be avoided by someone who knows what they're doing.
#5 fixing the volume drop:
as i said, i surrounded the small stone with a 4558 buffer/booster combo. standard stuff, really.
it seems it needs quite a bit more boost than before, probably because i skipped the input 2xtransistor stage of the effect and used the plain buffered guitar signal for the clean end of my mix.
#6 bright mod:
straight from the moosapotamus' mouth, i put in the 0.1uF instead of the 10uF.
didn't bother with a switch. i like my treble spanky, and i loved it as soon as i heard it.
really retains your original sound.
here's the schematic for my ramblings:
give it a go if you'd like.
let me know if it works for you.
oh, commercial modders: some cold hard credit would be nice if you feel like offering that depth thing.. wink wink, nudge nudge.
on the wish-or-want-to-try-list:
- get the effect to be more subtle at the twist of a knob (aka mix),
- a depth control might be nice (as in: amplitude of phase sweep)
- fix volume drop when pedal is engaged.
i found some of the stuff i needed on the net, came across some stuff i didn't think i'd need but sounded interesting, and couldn't find info on the depth control.
so, here we go.
#1, the classic: univibing. swapping capacitors in the phasing stages to get the sound closer to a univibe. liked the effect, didn't care for the option of swapping each stage individually too much, so i ended up throwing in a 4PDT, moosapotamus-style.
#2, the mix.
i tried what a lot of people refer to as a 'depth' mod, which alters the ratio of the mixing resistors and throws in a pot for the occasion. it does go from clean to vibrato (don't really like it as a vibrato, but ok). problem with this is that as soon as you flip the Color switch, you send phased signal back to the input to create extra resonance - and while that's nice, it also means your clean signal is now no longer clean, rendering this approach to the depth/mix mod sort of useless. to me, that is.
i tried running the feedback path to the second phase stage (like the Ross Phaser), seeing how that would solve that issue, but i didn't like the sound as much. it's still a valid idea, i guess, if you're into that kind of sound.
now, i already modded another small stone with a buffer in front and a booster at the end to compensate for tone suck/volume drop, and i was going to redo that with this one.
so i figured i could lose the mixing stage of the original effect altogether, take the buffered signal as the clean end for a new mix control, and still have the extra resonance the color switch provides.
works beautifully, as it turns out. you do get a slight volume boost at both extremes (the phasing effect is in the middle of the rotation, and it's always going to cost you some volume - nature of the beast) but i don't really mind. not enough to want to fix it, anyway.
#3, speaking of that color switch:
i altered the resonance/feedback path slightly. took out that half of the color switch and basically replaced it with a pot. 500K sounds exactly the same as no feedback at all, 10K minimum stops it from squealing - and you get everything in between.
the second half of the color switch messes with the LFO, and alters both the depth (the LFO's amplitude) and the speed of the effect.
i swapped it out with a SPDT because it was easier to position than the original bulky russian 2PDT.
i put in an on/off/on switch because it was what i had lying around, but the difference between the off position and the regular mode is so subtle i wouldn't bother with it too much.
since i was still hoping to find a solution for the depth control, i thought about fixing it in the deepest (color 'on') mode and bringing it down afterwards, but it turns out it still sounds a little different. maybe it messes with the waveform (haven't scoped it), or it shifts the whole waveform up slightly, i don't know. anyway, decided to keep it, in spite of coming up with
#4, a way to control the LFO's amplitude.
i read up on OTA's a bit, and i learned they spit out current rather than voltage. what's more, they do so based on the difference in voltage between their two inputs, much like regular opamps. so i figured if i wanted to control the amount of current coming out, i might as well try to control that difference.
and yes, if you hook pin #2 to pin #3, rendering the difference 0, the lfo shuts down.
i went the crude way and hooked up a 100K pot between both inputs. at 100K, behaviour is the same as before. turning the resistance down, the amplitude drops and the phasing gets more shallow.
there is a certain point where the speed is affected as well, and the whole thing speeds up quite dramatically. i don't mind. it can probably be avoided by someone who knows what they're doing.
#5 fixing the volume drop:
as i said, i surrounded the small stone with a 4558 buffer/booster combo. standard stuff, really.
it seems it needs quite a bit more boost than before, probably because i skipped the input 2xtransistor stage of the effect and used the plain buffered guitar signal for the clean end of my mix.
#6 bright mod:
straight from the moosapotamus' mouth, i put in the 0.1uF instead of the 10uF.
didn't bother with a switch. i like my treble spanky, and i loved it as soon as i heard it.
really retains your original sound.
here's the schematic for my ramblings:
give it a go if you'd like.
let me know if it works for you.
oh, commercial modders: some cold hard credit would be nice if you feel like offering that depth thing.. wink wink, nudge nudge.
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