Can someone explain this schematic symbol a bit more to me

[hesamadman]

Hi guys. I may be over thinking this but I guess thats what I do. Im still working on my Gretsch amp (when I have time), but the goal of building this amp was to keep gaining understanding. Im trying to understand the input jack and switched input schematic symbol.


The photo that I included is a schematic and a layout. What Im trying to wrap my head around is the switched input schematic symbol. On the Regular input there is a line connected to the ground and has an arrow pointing  to what I thought was the positive terminal. But on the layout the center terminal and the ground are tied together. I just don't understand where in the schematic it points that these two need tied together.


Sorry for the amature questions. Im trying to understand stuff very in depth before I move forward.

[kagliostro]

If I've correctly understand your question, the answer is that the connection must be done because in the jack intake those you see as to be connected together (the switch tip and the ground) aren't connected together as shown in the schematic, you must do the connection

Give a look to this different kind of jack intake and see if this can help you to understand it in an easily way

K

[chocopower]

--offtopic--


Kagliostro, that´s a really interesting input jack.

[hesamadman]

I guess where Im at is..... when I see this schematic symbol, I want to be able to create my own layout. But I don't understand that symbol enough to do so. When I see this symbol....do I ALWAYS just connect those two terminals?

[sluckey]

The arrow is actually a switch contact that is connected to the center terminal. With no plug inserted into the jack, the arrow (center terminal) makes contact with the tip terminal which carries the guitar signal. Your schematic and layout both show the center terminal jumpered to the sleeve (ground) terminal and also connected to ground. So the switch will ground the tip terminal when no plug is inserted. This will keep the grid of the preamp tube quiet when no signal is applied.

When you insert a plug, the tip terminal will be pushed away from the switch terminal, removing the ground connection from the tip and allowing the guitar signal to pass to the preamp tube.

[hesamadman]

The arrow is actually a switch contact that is connected to the center terminal. With no plug inserted into the jack, the arrow (center terminal) makes contact with the tip terminal which carries the guitar signal. Your schematic and layout both show the center terminal jumpered to the sleeve (ground) terminal and also connected to ground. So the switch will ground the tip terminal when no plug is inserted. This will keep the grid of the preamp tube quiet when no signal is applied.

When you insert a plug, the tip terminal will be pushed away from the switch terminal, removing the ground connection from the tip and allowing the guitar signal to pass to the preamp tube.

that did it brother. thank you so much

[sluckey]

When I see this symbol....do I ALWAYS just connect those two terminals? Modify message

No. You will wire it according to the schematic. That same three terminal could be used for your treble jack, but you would not connect anything to the switch (center) terminal.

[kagliostro]

The most common purpose of the switching tip is to ground the input of the amp (as to avoid noise)

so, when you see a switching input jack connected that way you know the purpose

Think at a jack inserted, the tip of the male jack connect to the corresponding part of the female jack and move it
with this movement the tip on the female jack isn't more connected to the input of the amp and so the input of the
amp is disconnected from ground and accept input signals

When you see such symbol on a schematic you must connect the switching tip of the female jack to ground
but remember that exist also female jack whose body is insulated from ground and you must arrange the ground
connection in one other place

---

@ Chocopower

Sometime I find those switching jack intakes at Ham Fest Flea Market and I get each time someone

they have a pair of SPDT switch, one acted by the tip of the jack the other acted by the sleeve

see type C




K


p.s.: Steve has the keyboard faster than mine - I posted at the same time but he was faster

[sluckey]

Those interesting looking jacks are very common in communications applications. A typical application would be at an Air Traffic Control Tower. There will be several 19" rack panels with rows of those jacks (even double jacks) used to patch radio audio from different controller positions to/from the actual transmitters and receivers. Makes it very easy to patch different radios to different controller positions.

Another application would be in a rack full of data modems in a situation such as a remote radar station that needs to send radar data to several different users, such as Air Traffic Control, USAF, Customs, etc. A jack panel would be used to patch various data (or control) signals to various modems that are connected via land lines or satellite to the users.

They are/were also used in the telephone systems. Remember the switchboard operators? Think Rowen and Martin's Laugh In.