pompira wrote:i've decided to be a bastard and ask more stuff anyway, even if it this might not be the most adequate place.
do you know when people talk about making readings with a multimeter,
they always say things like "measure between pin X and GROUND?
what if the amp isn't grounded?
what if it's an old amp with a two-prong mains cable?
or what if the amp has a three-prong mains cable but it's connected to an old socket without ground wiring?
does that mean the readings will be inaccurate?
does it mean the readings will be zero?
does it mean you'll fry your multimeter?
i appreciate that you've posted those links, but the only thing i could find that slightly resembles an answer for my questions is:
"Voltage is a differential quantity. To measure the voltage of a single point, a reference point must be selected to measure against. This common reference point is called "ground" and considered to have zero voltage. This signal ground may not be connected to a power ground. A system where the system ground is not connected to another circuit or to earth (though there may still be AC coupling) is often referred to as a floating ground."
could someone explain it to me as if i were retarded?
Voltage is always relative: one thing being measured with respect to another. Therefore grounds are also relative. There can be many different grounds in an amplifier. Where three-wire power cords are used, the ground wire is connected to the chassis. This is the "safety ground" and is there to shunt voltage to the earth in case there is a short in the amp that puts voltage on the chassis where it could harm you. Circuit grounds may be different: they are grounds relative to some other point in the amp that has a non-zero voltage. It is common practice for circuit grounds also to be connected to the chassis ground in at least one place, so measuring with respect to ground usually means measuring with respect to the chassis. It does not matter if the chassis is actually grounded at the wall for this to work. The chassis will always have an abundance of electrons relative to points with positive voltages which are electron-depleted (relatively).
Firestorm wrote:Voltage is always relative: one thing being measured with respect to another. Therefore grounds are also relative. There can be many different grounds in an amplifier. Where three-wire power cords are used, the ground wire is connected to the chassis. This is the "safety ground" and is there to shunt voltage to the earth in case there is a short in the amp that puts voltage on the chassis where it could harm you. Circuit grounds may be different: they are grounds relative to some other point in the amp that has a non-zero voltage. It is common practice for circuit grounds also to be connected to the chassis ground in at least one place, so measuring with respect to ground usually means measuring with respect to the chassis. It does not matter if the chassis is actually grounded at the wall for this to work. The chassis will always have an abundance of electrons relative to points with positive voltages which are electron-depleted (relatively).
