Small Stone Phaser... SWEET!

[Barcode80]

So i just built the small stone phaser project from tonepad, and it sounds AMAZING!!! fired up on the first try and everything! i only have two issues  that i need some help with:

i can still distinctly hear the effect in bypass. what is particularly odd about this is that the effect is grounded when in bypass, as the default switch wiring shown on FP's layout grounds the effect when off.

also, i can't seem to find the mod everyone talks about in the build reports that fixes the volume drop.

any thoughts guys?

EDIT: Nevermind. I'm a moron on both issues. Found the volume mods with the search, and i mistook the "color" switch for the bypass switch.

[Fp-www.Tonepad.com]

Cool.

Fp

[lynessmy]

Where do you get the IC? I heard it is almost distincted. You must be paying bucks for it...
I was almost ready to fireup the pedal but i don't have the IC...:p
Do you mind to share the pin voltage?

[Paul Perry (Frostwave)]

I believe the Tonepad version uses a more available chip than the original EH SmallStone.

[oldschoolanalog]

http://www.smallbearelec.com/Detail.bok?no=222
Just in case you need to repair an original...

[Barcode80]

yeah the ICs cost me about 25 bucks or so from smallbear, well worth it for this gem! a must-build.

[Fp-www.Tonepad.com]

used to be that ca3080 were $.70 way back when I did the adaptation for the small stone to use them. The ca3094 were like $4.90 so it made a lot of sense... I think it still does, just not as dramatic as it did.

Fp

[Paul Perry (Frostwave)]

Fp, time for a LM13700/NE5517 revamp

[Fp-www.Tonepad.com]

I know, i think the ropez layout could be adapted to smallstone specs. Must look into it sometime.

[paperhouse]

what chip does the RI small stone use? will the tonepad fit in an MXR sized box?

[Mark Hammer]

1) The Ropez board WILL fit in a 1590B.  You may need to file the ground traces at the sides of the board a little, but it will fit comfortably.

2) The LFO of the Ropez/Ross is virtually identical to the LFO from the first (6 chip) Small Stone.  With 2 small exceptions.
-   a) There should be a 22-47uf electrolytic cap between the 10k resistor from the LFO to the OTA control pins and ground.  The 10k/47u combination provides a lowpass filter the smoothes out the peaks of the hypertriangular waveform when the sweep rate starts to get faster than around 0.3hz (0.7hz with 22uf).  Makes the fast bubbly speeds sound nicer and much less choppy than stock.  Note that on the most recent Ropez layout there is an "extra" ground pad near the input pad.  Installing the smoothing cap is as simple as soldering the negative side of the added cap to that extra ground pad, and soldering the + side of it to the component side of the wire link that the 10k resistor is connected to.***
-   b) The 270k resistor from pin 1 to V+ in the Ross/Ropez is divided up into a 180k+100k series resistor pair in the original Small Stone.  The Color switch selects between connecting V+ to either the full 280k or 180k (the junction of the two series resistors).  This changes the sweep width and shape a bit, in addition to altering the speed a bit.  You could replace that 100k fixed resistor with a 100k pot to achieve variable width, although the range of adjustment may be less than you expect.  A 3-position switch that selects between 150k, 232k (150k+82k), and 271k (150k+82k+39k) might be more than sufficient.

A useful mod is also to replace the 15k feedback resistor on the last stage with something like a 47k resistor and 330pf cap (for hiss control).  That will give you about 3x the output of the original.  Now, replace the 150k terminating resistor with a 100k log pot and a 47k fixed resistor between the ground side of that pot and the circuit's ground (run a wire from the wiper of the pot to the stompswitch, instead of from the "output" pad on the board).  This mod will let you go from a noticeable-but-not-huge boost when the effect is engaged, to something a bit lower than bypass.  That way the pedal can be used as a solo effect (with a boost added) OR as a rhythm effect (with a slight volume drop) if you so choose.

With the variable regen instead of just 2 positions, the disaggregation of the Color switch into separate regen and sweep width, the replacement of the 27k phase-shift resistor to the mixer stage with a 27k+100k pot for phaser intensity adjustment, a dry lift switch for the clean-side (for vibrato), and the output level pot, you end up with 4 knobs (rate, regen, wet mix, level) and 2 toggles (vibrato, sweep width).  A very nice phaser without just enough control to accomplish a wide array of tasks, and sounds from in-your-face-intense to pleasingly subtle.  There is obviously more you can add (phase-filter option, range/offset shift, extra stages, stereo out, etc), but we'll leave well enough alone for the moment.

Although the board itself will fit in a 1590B, adding the assorted mods described here starts to stuff the available space with too many wires and things to fit comfortably in that space.  Two pots (speed, regen) and two toggles (vibrato, wide/narrow), or maybe 3 pots (speed, regen, mix) and a toggle (vibrato), or even 4 pots (speed, regen, mix, level), might fit in a 1590B with the board if your connecting wire is thin enough and the leads short enough, and the control/jack placement thoughtful enough.  You may just want to skip the strategic planning, though, and head directly to a 1590BB or a 125-size box to accommodate all the various controls and deluxe features.

Again, given the small footprint of the board, the inexpensiveness and availability of the parts, the sweep characteristics, the options for mods, and the ease of build, I don't know why anyone would even attempt the Small Stone instead of the Ross.

***(Francisco: There is probably room to add a pad to the board to solder the + side of that cap to the copper side of the board.)

[Barcode80]

would this work for the ross?

http://www.smallbearelec.com/Detail.bok?no=224

[Mark Hammer]

would this work for the ross?

http://www.smallbearelec.com/Detail.bok?no=224

It's what I use.

[Barcode80]

sweet! i already built the small stone and love the sound, but i might give the ross a shot since it is so much cheaper to build...

[s.r.v.]

are Mn3101 and MN3007's used in phasers and chorus? cause i have some after i took an old amp apart!   

[lynessmy]

sweet! i already built the small stone and love the sound, but i might give the ross a shot since it is so much cheaper to build...

ROSS? Ross phaser? where can i find the schemation or layout?

[s.r.v.]

http://tonepad.com/project.asp?id=25

[mdh]

are Mn3101 and MN3007's used in phasers and chorus? cause i have some after i took an old amp apart!   

Not phasers, but choruses and flangers.  The Small Clone (Clone, not Stone) on Tonepad is a nice chorus that uses those chips, and I'm sure there are others, as well.  I believe the Ibanez flanger on Tonepad also uses those chips, and the Ultra Flanger designed by John Hollis uses the MN3007, but not the MN3101.  I also have a DOD flanger that uses the MN3007/3101 combo, and there are many others.

[Mark Hammer]

The Corrral CE-2 clone on Tonepad is a very worthwhile expenditure of your effort and uses a 3101/3007 combo.  Years later, still a nice troublefree chorus.

[Fp-www.Tonepad.com]

You would think I've built all projects at tonepad, but I have not built the Corrral, only the Heladito, it uses MN3007 and CD4047 ics.

Fp