1/4 " connection?

[Jim Dempsey]

I just picked up some 1/4 (mono) phone jacks for an ext. cab i'm building.I have the 3 prong type.I know that tip=pos. and ring = neg.,but what is the other prong used for.Do i need the 2 prong type?--Thanks,Jim
P.S.--what gauge speaker wire?<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Jim Dempsey on 14 October 2004 at 05:35 PM.]</p></FONT>

[Bill Bosler]

Jim - Sounds to me like you have stereo phone plugs. Otherwise, you'd only have two solder lugs. There is no positive or negative on speaker leads because the signal is AC. Use the heaviest gauge wire you can comfortably solder to the lugs.<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Bill Bosler on 14 October 2004 at 06:31 PM.]</p></FONT>

[Jim Dempsey]

Bill,---It's says on a sealed Radio shack box.1/4" Mono-PHONO JACK,yes I thought it was for stereo too.It also states it's a 2-conductor-closed circuit panel mount.--Thanks ,Jim

[Jim Smith]

"Closed circuit" is the key. The third terminal shorts the positive connection unless a plug is inserted. I think these are used on some amplifier jacks for the second input of the same channel. For your application you can ignore it.

Here's a picture of one: http://shop.store.yahoo.com/byra/chasmounjac1.html

[Jim Dempsey]

Thanks Jim----I think as long as tip/ring are connected properly,I'll be alright.I'll just regard the other terminal,like you said.---Jim

[Donny Hinson]

That's right, Fender and other companies used these shorting ("closed circuit") jacks for speaker jacks on the old tube amps. That way, if you unplugged the speaker, the output transformer would see a "short" instead of a (potentially damaging) open circuit.

Solid state amps are just the reverse, open circuits are okay on the speaker, but a "short" will wipe 'em out in short order.

Either type of jack (open or closed-circuit) is fine for inputs.