Input/output jacks in schematic

[unpluggedman]

I need a little help with this schematic where input and output jacks are marked somewhat mysterious way to me. I believe the output jack shown below is supposed to be just a basic mono jack but in the schematic it has some extra connectors for some reason. Then is this interesting input jack. I'm not sure if it's a mono or a stereo. Why is the signal connected straight to ground before R1 and R2 and what is the R4 for? Is there something wrong with the design? Any help is appreciated.

[Seljer]

Those are NC (normally-connected) switching jacks. Imagine shoving in a plug and how the larger V shape bits would bend outwards and break the connection on the smaller Vs inside of the jack diagram. Both are drawn as stereo switching jacks with switchings lugs on all three terminals (so including the sleeve, not only tip and right) though the output jack is being used only as a regular mono jack.

On the input side the use of a switching jack accomplishes grounding the input when nothing is plugged in which is a nice feature because it silences the circuit instead of bringing on that distinct buzzing you sometimes get when you leave the end of cable floating in the air.

I can't muster what R4 is for either 


R1, like R45 and R37 are to prevent pop noises when switching

[duck_arse]

how is the sleeve switch actuated on those jacks, any idea?

[unpluggedman]

Thanks for your reply Seljer, it really cleared things up. I think I'm going to use a mono switching jack for input and thus be able to ground the input when plug is not connected. Maybe the R4 can be left out of the build or does anyone disagree? For output I'll use a regular mono jack without a switch.

[Seljer]

how is the sleeve switch actuated on those jacks, any idea?

Its the black plastic enclosed type (the way PCB mount jacks usually are) where the mechanism is identical on all three parts of the connector.

[davent]

R4, total mystery.

[duck_arse]

well, now you say, it's quite obvious. I'd never thought to try and draw one of those, circuit wise. maybe they had a bulk load of 6k2 they wanted rid of.

it would be interesting to see the jack plug that works both the tip and ring switches in the above drawn diagram, then turns 90 degrees to work the sleeve switch. as drawn.