Small Stone's color switch can be replaced with a pot?

[gigimarga]

Hello,

If my memory is still well working, I remembered that I found sometime ago a post in which sombody said that R.G. suggested a mod to replace the color switch of a Small Stone with a more useful pot.

I searched the forum, but i didn't find anything. Am I wrong?

Thx a lot!

[frequencycentral]

The Ross phaser is very similar to the Small Stone, but has a pot instead of a switch. 

http://www.tonepad.com/getFile.asp?id=99

[gigimarga]

Thx frequencycentral!
I know the Ross Phaser, but i don't know very well how to apply this idea to Small Stone...

[StephenGiles]

See DEVICE 11 page 5 - from 30 years ago!!

[frequencycentral]

See DEVICE 11 page 5 - from 30 years ago!!

Link? 

[slacker]

http://hammer.ampage.org/?cmd=lt&xid=&fid=&ex=&pg=10 

[StephenGiles]

http://www.4shared.com/file/110389163/a495e23/Sstone_mods.html

What's this - hold your hand day???

[frequencycentral]

What's this - hold your hand day???

Everyday is hold your hand day! 

[gigimarga]

Thx a lot StephenGiles and slacker!

Amazing article, but i must to be very carefully because i have a black russian Small Stone...

[gigimarga]

Very hard to make the mods without indications based on a schematic...can anybody help me?

[gigimarga]

Anyone translate these mods in the schematic? Please...

[Mark Hammer]

It is hard to know how much of the details of the mod article in DEVICE applies to a later-issue SS.  However, the Color switch will connect the phase-shift signal back to the input through a fixed resistor.  That fixed resistor willproduce some feedback, but not the maximum.  The best guess is to replace that fixed resistor with a smaller value (e.g., replace a 10k with 6k8 ot 8k2) and a variable resistor (at least 10x the value of the original fixed resistor) in series.  That will allow you to adjust the amount of feedback.

So how do you tell the difference between the feedback side of the Color switch, and the other side (which changes the rate and sweep width)?  For the middle lug on the feedback half of the switch there will be no positive DC voltage, since, as near as I can tell, all DC is blocked from reaching it.  The middle lug of the rate/width side of the switch, however, WILL show a DC voltage.

[R.G.]

N.B. - the color switch also dinks with the LFO in the small stone.

[gigimarga]

Thx Mark, thx R.G.!

Unfortunately, I don't understand anything yet...maybe you will be so kind to make references using this schematic: http://www.montagar.com/~patj/smlstone.gif (or another one).

Anyway, this wiring diagram http://generalguitargadgets.com/pdf/ggg_smallstj_lo1.pdf seems to be as in the article.

[Mark Hammer]

When the Color switch in that schematic is in the "on" position, the phase shift signal returns to the input, to be mixed with the clean signal, via a 3k3 and 27k resistor and 100n capacitor.  The switch will bypass the 270k resistor.  When you put the switch in the other position, the 270k resistor is now in circuit, and connected to ground, and the phase-shift signal that could be fed back to the input is also grounded.  So, no regeneration.

So, ignore what I suggested before.  Here is what to do instead:

1) put in a jumper instead of the 270k resistor.

2) omit the 4k7 resistor to ground (R12).

3) replace the 3k3 resistor (R11) with a 250k pot wired as a variable resistor.

You will now have a path from the last phase-shift stage back to the input, with a DC-blocking cap, and a variable resistance that will range from a minimum of 27k to a maximum of 277k.  That should provide lots of variation in regeneration amount.

[gigimarga]

Thx a lot Mark!

I will try it tonight, if i will have some time for.
Any suggestion for the sweep range pot?

[Mark Hammer]

Adsjusting the range of the sweep is something that I have only had minor success with.  If you increase the value of the resistor that goes from the LFO to the 4 CA3094 chips (or two 13600s, or....), that will reduce the sweep range, so that it does not sweep as high as before.  If the resistor is 100R, then I suggest using a 1k pot in series with the 100R for starters.

[gigimarga]

Adsjusting the range of the sweep is something that I have only had minor success with.  If you increase the value of the resistor that goes from the LFO to the 4 CA3094 chips (or two 13600s, or....), that will reduce the sweep range, so that it does not sweep as high as before.  If the resistor is 100R, then I suggest using a 1k pot in series with the 100R for starters.

Thx a lot Mark!

[Slade]

When the Color switch in that schematic is in the "on" position, the phase shift signal returns to the input, to be mixed with the clean signal, via a 3k3 and 27k resistor and 100n capacitor.  The switch will bypass the 270k resistor.  When you put the switch in the other position, the 270k resistor is now in circuit, and connected to ground, and the phase-shift signal that could be fed back to the input is also grounded.  So, no regeneration.

So, ignore what I suggested before.  Here is what to do instead:

1) put in a jumper instead of the 270k resistor.

2) omit the 4k7 resistor to ground (R12).

3) replace the 3k3 resistor (R11) with a 250k pot wired as a variable resistor.

You will now have a path from the last phase-shift stage back to the input, with a DC-blocking cap, and a variable resistance that will range from a minimum of 27k to a maximum of 277k.  That should provide lots of variation in regeneration amount.

Thanks a lot, Mark, it help us all.
Could you explain more extensively the function of the cap? I'm really interested in this.
Greetings!