Click here for a pdf version of the schematic for the "official" D-TAR Solstice footswitch. It is special in that it has both the proper wiring to preserve the Solstice front panel "Mute" LED function and its own Mute LED. It is popless when used with current production Solstice units, in agreement with the Glen Phillips comment in his Frets Magazine review of the Solstice. (Glen worked with us when we designed the circuit changes for the Solstice that cured the popping, so he had advance information.) Note that the footswitch requires a STEREO (a.k.a. "TRS") cable to have the Mute LED work properly, because the LED switching uses the "ring" circuit, which is not present in the more common monaural guitar cables.
As an alternative, any footswitch that shorts the tip of the 1/4" plug to ground (almost all of them do that) will perform a basic mute function with the Solstice. It will also be popless with current production Solstice units IF A MONAURAL (NOT Stereo) CABLE IS USED. This arrangement will not, however, switch the front panel "Mute" LED. Thus there is no visual indication of muting when a generic footswitch is used, and this can lead to an embarrassing situation for performers.
A few off-the-shelf footswitches can control the mute LED correctly when used with a STEREO cable, but they will INVARIABLY inject a pop into a Solstice. Thus this may not be a usable option for most players, and is not recommended. The only known way to have a popless footswitch AND a working Mute LED is to use the "official" DTAR footswitch design.
Note: Any Solstice which pops when muted or unmuted, either with the front panel pushbutton or the "official" external footswitch design, is from an early production lot and some level of popping is considered to be normal on those units. The popping, while audible, is not so loud as to be a problem for most users. Although it is possible to update an early production unit to eliminate the popping, it is so time-consuming that we do not do it - ever - so please don't ask. In contrast, the residual mute/unmute popping on current production units is essentially inaudible, even under studio conditions.
As you can see from the attachment, the schematic has a grand total of five parts, and so can be built, either from scratch or as a mod to an existing generic footswitch, by anyone with a rudimentary knowledge of electronics. All of the parts are readily available from Radio Shack, Warmoth, Allparts, as well as most neighborhood electronics parts stores (Fry's Electronics, MarVac, etc.).
Building a Mute Footswitch for the DTAR Solstice
The pushbutton switch:
It is DPDT switch, latching ("ON-ON") type. We used a Carling 316-PP industrial-grade switch in the prototype, and that switch is available from Mouser Electronics, as well as many electrical/electronic supply dealers. The AR70736 from MCM Electronics may also work, or possibly the Carling 64112220 from Digi-Key Corporation, but we haven't tried them (let us know if you do). The middle pair of switch terminals go to the stereo jack and the capacitor. Pick either remaining pair and connect those to the resistor and ground/common. (See the footswitch box schematic.)
Other parts:
Pretty much any ordinary LED (Light-Emitting Diode) will work. A high brightness type is, well, brightest, which is usually a good thing. I recommend going to Radio Shack and picking one that has the highest mcd (millicandle) rating. I've seen some "super red" types that claim 4000 mcd (4 candlepower) - when run at very high current. The current is not that high in the Solstice, but a high-brightness LED will still be brighter than a standard LED, even at low currents. When connecting the LED, remember that the "cathode" end of the LED is usually the shorter lead, or the lead next to small flat on the bottom flange. The cathode lead connects to the capacitor and footswitch.
The 10uF ("ten microfarad") capacitor is totally non-critical. An aluminum electrolytic capacitor or a tantalum capacitor would be my first choice, because they are cheap and readily available. Radio Shack 272-1013, 272-1025 and 272-1436 are good examples. The "+" terminal connects to the footswitch, and the "-" terminal connects to ground/common.
The resistor is totally non-critical as well. Pretty much any old 1K ("one thousand ohm") resistor would be just fine. Radio Shack 271-1118 or 271-1321 are typical examples. It doesn't matter which end of the resistor goes where.
The Radio Shack 274-312 is a good example of a stereo TRS jack, and similar jacks are available at many audio or guitar dealers, as well as many electronics distributors. The schematic symbol is a good approximation to the mechanical structure of the jack, so compare the jack to the schematic if you're not sure what goes where.
Building the Muting Pedal:
Use a metal box to avoid hum pickup, and be sure that the metal box is electrically connected ("grounded") to the metal bushing of the stereo jack for the same reason.
Solder all of the connections - if you don't, the connections won't be reliable and you'll be kicking the footswitch to get it to work. If you aren't comfortable with doing the soldering yourself, your local electric guitar repairman may be willing to help with that.
You pretty much can't hurt the Solstice with a wiring error in the footswitch, so don't worry if it doesn't work right when you first try it out. Rest assured that it will work properly if it is wired properly, and no harm will come if that doesn't happen the first time. If you're not sure how to connect up all of the electronic parts, ask for help from someone who has done some work with electronics. Basic electronics knowledge is pretty common today, but if you don't know anyone who can help, try a nearby high school, college or university. Most instructors in any of the physical sciences either have, or know someone who has, a basic knowledge of electronics. The same is true of most amateur (ham) radio people, and computer repair people, so help should be available without too much searching.
If the footswitch box is wired correctly, it shouldn't have any bad habits, such as "tone sucking", popping or buzzing. The LED on the footswitch should agree with the LED on the Solstice. If these things are not true, something is wrong, and the most likely problem is a wiring error. Also, remember that you must use a stereo (a.k.a. TRS, or Tip/Ring/Sleeve) cable with the footswitch. Most guitar cables are not stereo, so look for the extra contact on the plug (it looks like a stereo headphone plug) to make sure that you have a stereo cable. Also, the cable must be shielded (most are), or you will have lots of hum and buzz. Your local Radio Shack has shielded stereo cables, and your local guitar dealer probably does, too.
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