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Trouble reading schematics

  1. Aug 1, 2005 #1
    Hi, I am just getting into building circuits. I have found a nice page with all the symbols: http://library.thinkquest.org/10784/circuit_symbols.html which has helped me some but I still get confused. The circuit I am talking in regards to is this: http://tangentsoft.net/audio/cmoy-tutorial/misc/cmoy-tangent-sch.pdf . As a reference, here is the page for the pocket amplifier.

    It is a pocket amplifier for headphones. I hope to be able to make a small amplifier for a guitar, and I figure this is a start.

    First of all, on the far left side, those symbols where it says 9V are for grounding right? What exactly is being grounded. I understand that there is a 9V battery used but doesn't that just have positive and negative terminals (shown on the far right)? What exactly is being grounded?

    Also, Capacitor 1 (C1). Having a plus or minus means it is polarized right? Since the positive is connected to the negative by a line, doesn't this mean that the two terminals are directly connected? Should that be a concern?

    What does the SW 1 \ 2 mean along the top? My guess is that it is a switch that will either connect the circuit there or disconnect it there. (I am only referring to the first schematic in the document for all the preceding questions)

    On the second schematic, I see the potentiometer is being used as a volume control because it is a voltage divider. If I already have a volume control that controls the volume of the input signal (this is an amplifier circuit), do I still want the pot? If not, how would I get rid of it and keep the amp at full power always?

    The capacitor 2 in the second schematic appears as though it is unpolarized and is just connected in series there, is that correct? What is the purpose of this? To prevent some sort of overload or other hazard?

    It also appears as though R3 and R2 are just kinda connected off to the side and then grounded. What is the purpose of this? is this to decrease current in a proportional sort of way as the potentiometer is adjusted?

    It also looks like there is an integrated circuit there, how do those work? This is the op-amp, right? It looks as though tehre are five different terminals.

    Please excuse me if my questions seem stupid or very novice, because I haven't taken any classes on this, and haven't built anything yet.
    Last edited by a moderator: Apr 21, 2017
  2. jcsd
  3. Aug 1, 2005 #2


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    These are the two 9 volt batteries. No grounding here. The +9V, -9V, and ground symbols on the power section connect to the same symbol points on the amplifier section.
    This ground symbol is not an earth ground. It's just a reference or common for the circuits
    yes, there are two capacitors called C1 connected together. This is the common reference point.
    This is the power-on switch. The 1 and 2 refer to the switch terminal number.
    I would keep it.
    The capacitor feeds the AC signal to the amplifer and prevents DC from your source from getting through. It along with R2 provides a little load. R3 and R4 determines the gain on the amplifier.
    yes. You should research a little to find out how op amps work. This circuit show your two inputs, one output, and the two power terminals(+ & -).

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