New Small Stone LFO Mod

CynicalMan · February 02, 2010, 05:35:05 PM

Just about the only mod you can do a nano Small Stone

I've been modding a lot recently. In the past couple of days I finished modding my GCB-95 Crybaby and my MXR Distortion III (look for reports soon on my website) and I'm now looking to mod my Small Stone. Only one problem. I have the surface-mount filled nano Small Stone. When I opened it up, this is what I saw:

I thought, OK I'll do the vibrato switch, i only have to desolder a resistor. I start comparing it to the schematic. It's nothing like it. In the nano small stone, there are no transistors, two opamp, two surface mount diodes, around 5 electrolytic caps, and many of the resistors have values like 27.4k or 392k. Tracing is impossible as the board is double-sided and many of the traces go under components. I quickly realized that any existing mods would be useless because I wouldn't be able to tell where to do them and because I wouldn't be able to solder them anyway. So I focused on making mods on the things I could solder to: the pot, the electrolytic caps, the jacks, and the 3PDT switch, and I found a great mod the lets you select sine, reverse sawtooth, or sawtooth LFO waves.

The sawtooth and reverse sawtooth modes are nice for having a more rhythmic sweep, more pulsating than swooshing. They are both faster than sine. I don't know if this would work for Small Stones other than the nano. Someone with a big Small Stone should try it out.

Because of the shape of the PCB, the switch would have to be installed like this:

Sound clips coming soon...

CynicalMan · February 02, 2010, 07:10:39 PM

Here's a sound clip:

http://sites.google.com/site/distorque/home/projects/sound-clips/SmallStoneLFOModDemo.mp3

Bypass - Normal (Sine) - Sawtooth - Reverse Sawtooth

Mark Hammer · February 02, 2010, 08:39:27 PM

Neat!!

alex frias · February 02, 2010, 09:38:16 PM

Simply elegant!

opticnerv · February 05, 2010, 09:42:08 PM

I like your mod and might like to try it. But I'd need more details/pics on how to do it as I have some, but not a lot of experience modding pedals.

My Nano SS has a noticeable volume drop when it's engaged. Do any of you have suggestions on remedying this?

I found this vid on youtube of a modded Nano SS with volume and depth/tone pots installed!! Unfortunately, it's in Japanese.
http://www.youtube.com/watch?v=YFr4yqpymYk

K

CynicalMan · February 06, 2010, 12:52:52 PM

Quote from: opticnerv on February 05, 2010, 09:42:08 PM
I like your mod and might like to try it. But I'd need more details/pics on how to do it as I have some, but not a lot of experience modding pedals.

My Nano SS has a noticeable volume drop when it's engaged. Do any of you have suggestions on remedying this?

I found this vid on youtube of a modded Nano SS with volume and depth/tone pots installed!! Unfortunately, it's in Japanese.
http://www.youtube.com/watch?v=YFr4yqpymYk

K

You might be able to add small pots on the side, but the wiring would be very cramped and it's very hard to wire to surface mount parts. Because of this my mod only adds a switch (less cramped wiring) and only solders to the pot, which is much easier to solder to than the surface mount parts. I'm not doing this mod for maybe a month (part shipping $:-\$ ) so I can't get you any pics, but I will draw up a wiring diagram when I get the chance.

I'm surprised your small stone has a volume drop. Mine doesn't, aside from a bit of compression. I thought that was one of the things EHX fixed with the new Small Stones. The normal fixes for it wouldn't work anyway, because the boost and mixer sections have been replaced by opamp sections.

opticnerv · February 06, 2010, 02:02:53 PM

Unsure just when mine was manufactured - maybe that has something to do with the volume drop? Looking forward to the info on your mod unless I just decide to get rid of this and find something that serves my needs better. Thnx.

spectraljulian · February 06, 2010, 07:47:34 PM

hmmm I wonder if I can do this to my Russian Stone. I also really should do the volume mod sometime.

CynicalMan · February 07, 2010, 10:02:40 AM

Here's the wiring diagram:

Quote from: spectraljulian on February 06, 2010, 07:47:34 PM
hmmm I wonder if I can do this to my Russian Stone. I also really should do the volume mod sometime.

Like I said earlier, this might only work for the nano Small Stone, which has a different LFO. Still, it's easy to try once you get the box open. I don't know what kind of pots are in the Sovtek Small Stone, but with mine I just could drop the diodes into the conveniently placed holes in the pot.

ddpawel · June 01, 2010, 12:41:15 PM

Do You think this kind of mod will work for other OTA phaser, I mean TOnepad Ross Phaser? Someone tried this mod?

CynicalMan · June 01, 2010, 03:48:19 PM

I've done it on the nano small stone, but I haven't done it or heard it confirmed for any other phasers. Looking at the schematic, my gut feeling is that it probably wouldn't work, but it might. The ross phaser's LFO seems different from the small stone's.

Gila_Crisis · June 01, 2010, 05:27:35 PM

this mod look like the symmetry pot mod for the tremulus lune which is the same a paar of diodes (controlled with a pot) in parallel with the speed knod. I think it should work on every speed pot of whatever modulation effect.

ddpawel · June 02, 2010, 12:43:41 AM

Thank You. I've also noticed that it looks like Tremulus Lune symmetry.
But Ross Phaser also have OTA LFO (instead of Small Stone op-amp), which is very sensitive to voltages and currents. Will it be safe? What do you think. I don't want to burn my LM13700 (expensive in my country).

CynicalMan · June 02, 2010, 03:56:05 PM

Quote from: Gila_Crisis on June 01, 2010, 05:27:35 PM
this mod look like the symmetry pot mod for the tremulus lune which is the same a paar of diodes (controlled with a pot) in parallel with the speed knod. I think it should work on every speed pot of whatever modulation effect.

My guess is that this works on LFOs where the speed pot is wired with 2 connections, and resistance at minimum is the fastest speed.

ddpawel, if you're not comfortable with mucking around with OTAs, just don't try it out. Personally, I don't find it that useful.

ddpawel · June 02, 2010, 04:06:53 PM

I've searched and found great site http://www.falstad.com/circuit/e-index.html . I've tried generators & oscillators and 've found that if I wired diode around resistor responsible for speed it really gives sawtooth wave on output. So I'll try this mod with Ross Phaser. If it works with so many examples it should work with OTA LFO.

haima · July 20, 2010, 08:41:15 AM

i just tried this mod with my tonepad small stone clone - didn't seem to work. one diode direction did increased LFO speed, but not the max speed - the diode switch just has the same effect as moving the pot up a bit, until you get to top speed, then the diode switch has no effect.

the shape didn't seem to change at all - from what i could see on my scope and what i could hear.

has anyone else tried this with a non "nano" small stone?

spectraljulian · July 20, 2010, 12:43:41 PM

I can try it on my sovtek later today

LRonKnieval · March 10, 2012, 12:13:14 AM

I just finished this mod on my Small Stone Nano and I love it. The Sawtooth does some really rapid oscillation in conjunction with the color tone. I was even able to get the toggle on the face, though I had to do a bit of insulation on the inside of the box. Thanks for posting this really cool, really easy, really cheap, and really useful mod.

joelindsey · March 14, 2012, 02:20:03 PM

I can confirm that it does not work with the Behringer Vintage Phaser.

lemonengine1 · June 22, 2016, 11:35:00 AM

Sorry to bump an old thread, but I'm wondering what value diode(s) do you use for this mod? Thanks in advance!

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New Small Stone LFO Mod