Small Stone mod

[bulldogguitars]

Does anyone know how hard it would be to add a blend pot to the small stone. For control of the uneffected versus effected signal. I was thinking it would be just the addition of a pot to control the balance of the signals. Thanks for your help, Danny

[bulldogguitars]

bump

[Mark Hammer]

It's easy. The key component is the 27k fixed resistor that links up with the 30k resistor just before the .1uf cap at the output. Stock, it provides a phase-shifted signal that is matched in level with the straight signal arriving via the 30k resistor. If you increase the resistance beyond the 27k, you move the phase-shifted signal to the background and the notches are not as pronounced.

Simplest way to do this is to remove the 27k resistor and solder it to one lug of a 100k pot. Now, run a wire from the 27k resistor to one of its former pads, and run a second wire from the adjacent pot lug to the other available pad. The larger the combined resistance of fixed resistor and pot, the subtler the phase-shift effect will be.

Some folks like to aim for a wet-dry balance pot. Personally, I'm not a big fan. The first reason is that it is tough to estimate the circuit changes that will produce the desired effect. More importantly, though, I've simply never found a use for mixes where wet was somewhere between 50% and 100%. I have found a use for mixes where wet signal was <50%, though. So, what I recommend is to have a toggle to lift one end of that 30k resistor for producing vibrato effects, and the suggested 100k pot to produce subtler phaser effects.

[bulldogguitars]

Mark thanks alot I appreciate it. Im going to exeriment with this and see how I like it. Ill let you know, thanks again Danny

[Mark Hammer]

You're welcome. Take a gander over at http://moosapotamus.net/THINGS/things.html for some ideas about what you can do with these beasts.

Note that the Color switch changes the sweep width and the regeneration amount at the same time, using the two halves of a DPDT slide switch. It is a simple matter to unyoke the two changes and have separate switches for width and regen.

Honestly, if someone was smart, they'd start selling mods for these things, because there are a zillion things you can do with them and the classic chassis accommodates lots of switches and extra knobs. I'd do it but I don't have the time.

[bulldogguitars]

Mark, thanks alot for the link. I really need to investigate these pedals more. I knew they were capable of so much more. Thanks again, Ill keep you posted of my results. Danny

[bulldogguitars]

Mark does it really matter which lug you hook the 27k resistor to. I have it going to the middle lug. And should the third lug be grounded or does it matter. As of right now I dont and when turned down to essentially bypass the effect. You still have a little of the effect coming through, which is ok that doesnt bother me so much. I also did the volume loss mod and replaced the 4.7k resistors with 10ks that are in the feedback loop on the input trannys and honestly the volume is worse. Since ive added the blend pot should i probably go the other direction with the resistors. Thanks for your help, Danny

[Mark Hammer]

When all you need from a pot is one varying resistance, as opposed to one which gets smaller as a second one gets bigger, you can use only two lugs (wiper and one side-lug) if you feel like it. With th pot shaft facing you and the lug pointing downwards, you would use the wiper and lug on the right if you wanted the resistance to get smaller in a clockwise direction. Use the outside lug on the left if you want the resistance to get bigger in a clockwise direction. In our case, we want it to get smaller in a clockwise direction.

It is considered a good practice, however, for people to use all three lugs by tying the wiper and unused lug together. Why? Well, the wiper is supposed to maintain contact with the resistive strip at all times, but that is only a promise, and not one the pot can honour for all time. By connecting the wiper and other outside lug, you are assured that even if the wiper failed to make contact with the resistive strip, there would never be an open circuit, and the resistance would always revert back to the maximum of whatever the value of the pot is. Not critical, but good insurance that only costs you the price of an extra solder joint.

[digitalmike101]

Hello Mark Hammer and Bulldogguitars,

I have this phaser and love it. The boss phasers are garbage tone suckers. The ONLY issue is the intensity of the phase is too much depending on what you are playing. I want to do this mod and the directions are very
straight forward. The only thing I need to know is where the resistor (the 27K one) is physically one the board. If anyone has the number of the resistor (Example - R28) on the board that would be helpful.

Thanks!

[digitalmike101]

BTW i have the one of the most recent small stones (EH4800). it looks like this.

Electro-Harmonix Small Stone Reissue

Thanks,

[doctor]

BTW i have the one of the most recent small stones (EH4800). it looks like this.

Electro-Harmonix Small Stone Reissue

Thanks,

You need to remember that maximum phaser effect is obtained when amplitudes of
direct and processed signals are equal.
For this reason blending effect can be got only by decreasing of the processed signal
(i.e. increasing of the 27K resistor).
It follows that potentiometer about 100K should be connected serially with 27K resistor.

Here is genuine Small Stone schematic (with true bypass).
I hope it will be helpful.

[digitalmike101]

Based on this schematic, I conclude that R24 is the resistor I have to take off.

Is this right?

Thanks