Re: Took my amp to a tech today...
benjaturner said:
Sorry that I can't give any more information on it but I was hoping someone might be able to explain some of the basics about this secondary coil to me. He's gonig to ring in a few days to tell me what he thinks I should do and I'd like to be in a position where I've got some clue what he's talking about. I had a read of Aspen Pitman's Tube Amp Book regarding the matter but I couldn't find much that I could understand.
1.) A wire passing through a magnetic field creates current flow in that wire. Or conversely, a magnetic field moving past a wire will induce current flow in that wire (either the wire or the magnetic field has to move).
2.) Current flowing through a wire will create a magnetic field around that wire.
In a typical transformer, the primary coil (windings of wire) is connected to an AC power source. Current flowing through the coil creates a magnetic field around the coil. Since the power source is AC (alternating current) the direction of the current flow and the magnetic field alternates back and forth.
The secondary coil(s) are not physically connected to the primary coil (isolating the input of the transformer from its output) but instead placed close enough to the primary coil that the primary coil’s
magnetic field surrounds the secondary coil(s).
Since a moving magnetic field induces current in a wire (see #1), the alternating magnetic field from the primary coil creates current flow in the secondary coil(s) (again without any physical contact).
:cool3:
Voltage is directly proportional to the ratio of windings between the primary and secondary coils. If a primary coil had 10 windings and a secondary coil had 1000 windings, the voltage produced in the secondary coil would be 100 times greater than the voltage applied to the primary (and of course current would be 100 times less – you can’t get something for nothing) This would be an example of a “step-up” transformer. If you reversed the ratios you would have a “step-down” transformer.
In it’s basic form a transformer is about as simple as it gets… Two or more coils of wire (not connected to each other) in close proximity, usually wrapped around a ferrous core (for magnetic field strength).
Now that being said, it gets a bit more complicated in actual use – in addition to the previously mentioned variables - voltage and current there is a third variable I haven’t mentioned yet called resistance. A very simple equation (Ohm’s law): current (I) = voltage (V) divided by resistance® makes up the ‘backbone of electronics. If you know any two variables you can calculate the third.
Resistance and reactance (damn another term) :smack: :ugh1: impede the flow of current. The term impedance refers to the relationship between these two variables. ..
At this point it is getting way too complicated for a layman’s discussion of transformers. The only reason I started down this path is to illustrate how complex the selection of a couple of pieces of wire can get.
An amplifier designer needs to match the voltage and current requirements of the amplifier with the impedance requirements of the speakers. Choosing the wrong impedance selection or disconnecting your speakers with power applied creates a power mismatch in the coils of a transformer. This in turn causes reflected energy / heat to build up which can damage / open up a coil.
:banana:<--just for the fun of it.
:cool3: