I am trying to find a 1/4" female chassis-mount phone jack that will switch my 9 volt power ON when a plug is inserted. This is for a small buffer box for my steel guitar, to go between my instrument and my volume pedal. I can't seem to find these. What am I missing? I know that most stomp boxes have these.
You need a standard stereo socket and place the negative battery lead on the ring contact, negative preamp wire on the sleeve and signal on the tip. Positive battery is connected all of the time. As a mono plug is inserted, the negative battery wire is connected to the sleeve or ground and powers a return for the battery making the pre amp active.
Understanding Guitar Wiring | stewmac.com
Understanding Guitar Wiring | stewmac.com
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That often results from adapting 50+ year old schematics drawn in the germanium days when the positive lead WAS switched by the guitar cable.
Still guitar players of the day would curse the old Boomer wah-wah pedal because it ate batteries. The player would yank the cord out of the guitar leaving the other end in the wah-wah pedal, switch off the amp and walk away. The oddball round battery would last one or two days max.
I worked in a practice studio where bands would rehearse with a live tape machine running to get their act together before the big week at Criteria would cost them (or the record label) big $$$$$.
I tried to explain this to the guitar player of a big name act in about 1971 or 72. Out of frustration he threw the wah-wah pedal against the wall one day. It lay on the ground where it landed for the remaining time that the band was there, and was left behind on exit. I grabbed it, and still have it.
I might have taken apart their Vox Tone Bender fuzz pedal to trace it's schematic and put it all back together before they arrived one day......I still have my clone of that pedal. It too used the same switching arrangement, but used a common 9 volt battery and it lived for over a week when left on.
I have used ones with two independent single pole, double throw switches in addition to the usual ground, ring, and tip contacts. This gives you a lot of flexibility in terms of switching, but it also makes 9 contacts you have to sort out with an ohm-meter before you can figure out how to wire them up.
Here in BC, a Vancouver electronics store carries them:
1/4" STEREO CHASSIS JACK W/ SPDT SWITCHES 24-697-0
In the USA, various guitar-centric small businesses seem to carry them:
1) 1/4" Stereo, Isolated DPDT Switch - Small Bear Electronics
2) 1/4" Stereo Isolated Chassis Jack w/ 2 SPDT Switches - GuitarElectronics.com
-Gnobuddy
Can´t find a picture now, but I have seen 1/4" jacks with independent/floating switches.
* One type is Factory made, carries an extra leaf switch (2 contacts), normally open, which are pushed together by plug tip.
To insulate them from everything else, plug tip does not touch leaf directly but through a nylon "button".
I´ve seen these in Fender amps, which are famous for the unique multipin jacks they use.
* a homemade kludge which I found in active Bass preamps, so they could use split +/-9V rails .
One is switched the normal way, for the other they added an Epoxied industrial type "microswitch" so plug tip pushes the orange nylon button:
* One type is Factory made, carries an extra leaf switch (2 contacts), normally open, which are pushed together by plug tip.
To insulate them from everything else, plug tip does not touch leaf directly but through a nylon "button".
I´ve seen these in Fender amps, which are famous for the unique multipin jacks they use.
* a homemade kludge which I found in active Bass preamps, so they could use split +/-9V rails .
One is switched the normal way, for the other they added an Epoxied industrial type "microswitch" so plug tip pushes the orange nylon button:
An externally hosted image should be here but it was not working when we last tested it.
I simplified R.G. Keen's idea to switch just a single positive rail using one PNP small-signal transistor. An ordinary (non-switching) stereo jack is used.
The idea is that inserting a (mono) plug will short the ring connector on the stereo jack to ground, turning on Q1, which in turn applies power to the FX circuit board.
This circuit has not been built and tested.
-Gnobuddy
The idea is that inserting a (mono) plug will short the ring connector on the stereo jack to ground, turning on Q1, which in turn applies power to the FX circuit board.
This circuit has not been built and tested.
-Gnobuddy
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Oh what a difference a single wrong connection makes...thanks for the catch! (I "saw" the right thing in my head, of course, but unfortunately that didn't translate to where I clicked the mouse on the screen. )
Corrected version attached. LED current terminated to ground where it belongs, not to signal input into FX circuit.
In my recent builds over the last three or four years, LED current is typically 100 micro amps, or one-hundredth of the old standby 10 mA. I use LEDs rated over 5000 mcd, which combined with the usual 20 mA max current invariably means they are more than bright enough to act as an indicator at 100 uA.
-Gnobuddy
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