Small Clone Mod

[jimbob]

A while back I asked how to wire up a switch for cap selection on the Small Clone. I think this was a Mark Hammer mod. Anyways, the switch wont fir into the enclosure so I want to just place a small switch that select between 2 caps. I think this would be a spdt? And if so...any pics of a wiring diagraph?

thanks'

James

[Mark Hammer]

Which cap selection is that?  Is it one for speed range, for delay range, or for trimming the bass off the wet signal?  The first one can be situated just about anywhere.  The third one only has a few constraints on where you stick it.  But the middle one (delay/clock range) ideally needs to be situated as close to the original cap as you can manage, otherwise stray signals and audible whining starts to become an issue.

As near as I can surmise, any of these can be done with an SPST switch, for which an SPDT will obviously sub very nicely.

There are several methods to use.  One is to use the switch to add another cap in parallel.  Simple enough.

Another is to use the switch to shunt a cap.  For instance, if you wanted to select between trimming back the wet low end or not, you'd wire up a small-value cap after the 1uf cap after Q2 to reduce low end in the wet path.  The switch would be wired up in parallel to the cap (and here you could simply wrap the ends of the switch leads around the base of the cap leads), and when you close the switch, it's like the cap isn't there.  Keep in mind the effective capacitance is largely a function of the smaller cap.  So, if you had 1uf in series with .047uf, their combined series value would be .045uf.  Shunt the .047uf cap and it reverts back to 1uf.

For the clock-range switch, see the John Hollis Zombie for an example of how its done.  In the case of the Zombie, the normal arrangement is to use two identical caps tohalve/double the clock range, but you don't have to restrict yourself to that.  For example, if a modest shift suited your tastes, you might consider using 150pf in series with 270pf.  Together, the capacitance is around 96pf.  Shunt the 270pf one and the value goes back up to 150pf.  If you wanted a "deluxe" arrangement, get a 3-position centre-off SPDT toggle, and wire it up so the switch common is tied to the junction of the two caps, and flicking the switch to the sides shunts the one cap or the other.  N series they make 96pf.  Shunting the larger one gives 150pf, and shunting the smaller one gives 270pf.  Not quite a perfect proportional change, but not wayyyyyy off either.

[jimbob]

Awsome Mark!

Thanks for your time!


BTW- it was for the speed


James

[jimbob]

OK- I got a spst and placed a 330pf on each side. I think that means one side will be 330pf and then the next side will be half of that? It seems either way there is still a neat difference between the 2 w a flick of the switch. This mod remids me of a pedal i sold last year called the Rocktron Vertigo Vibe...which as I look back was a chorus pedal with a spst switch to increase the cap size like the small clone. [urlhttp://www.musiciansfriend.com/srs7/g=guitar/s=effects/search/detail/base_pid/154223[/url]

[george]

Awsome Mark

Mark Hammer you should have that as your signature 

[jimbob]

OK- I thought I had it. I originally got a spst and placed a 330pf on each side. I think that means one side will be 330pf and then the next side will be half of that?

It seems that there is only an effect w one toggle of the switch. The other in just sound w out the chorus. Any idea what I did wrong here?

I was trying to use a switch between 2 diff size caps. One with a typical 150pf sound and the other w something more extreme. Instead, only one toggle of the switch does anything.

Ideas?

[Mark Hammer]

Hmmm, we might be mixing up caps here.  The Rocktron Vertigo seems to have one switch to cancel the dry signal (for "Vibe" mode), and a stompswitch to go between faster and slower LFO modes.

"Faster" can mean a couple of things, which maybe we need to get straight.  One is the range of LFO speeds, and the other is the range of clock speeds.  The range of LFO speeds is given by the 2.2uf capacitor between pins 1 and 2 of IC2 in the Tonepad layout.  The range of clock speeds (hence, delay time ranges) is given by the 150pf cap.  Just so you know, that will NOT replicate what the second stompswitch on the Vertigo does.

To shift the delay range of the SC with a SPST switch, you can do the following:

1) Solder one leg of one of the replacement caps to the pad right near pin 1 of the 4047.
2) Solder one leg of the OTHER replacement cap to the pad located near pin 14 of the 4047.
3) Solder the two free cap legs together.

Okay, now you have a series combination whose total capacitance is given by 1/Cx = 1/Ca+1/Cb+......  In this instance Ca and Cb are each equal to 330pf, hence their series capacitance is 165pf.

4) solder a *short* lead to each leg of ONE of those capacitors.
5) solder those leads to the common and outside lug of a SPST toggle

When you flick the switch, this will shunt/bridge ONE of the caps, making the effective capacitance equal to 1/Cx = 1/Ca + 0.

That should work, barring any bizarre mishaps.  Make a point of installing the switch right above the spot where the caps are, which would situate it just in front of the Depth control - a convenient, and conceptually appropriate location.

[jimbob]

Great - Ill give it a try.