As Scott Joplin has pointed out that's what transistors and opamps etx. do.
AC power comes from the wall outlet, goes into the power supply where it's converted to DC that is used to power the various parts of an amplifier.
The audio signal comes in from the input jacks (usually RCA) and is coupled to the controlling elements of the amplifier's transistors and other circuits, where it is amplified (made bigger) and passed along to the next stage. Each transistor, op amp, chip, etc. uses DC power to enable this to happen.
The attached thumbnail shows an extremely basic transistor amplifier, the general building block on which all amplifiers are made.
The DC power to operate this circuit comes from the battery (V1) on the right.
The AC signal comes from the signal source (V2) on the left.
The transistor in the center and it's 4 resistors take that signal at IN, with a small current, then amplify it producing a larger current, drawn from the battery and sending a larger version of the signal to the OUT pin in the drawing.
The graph at the top shows the small input (green) and larger output (red) taken from the IN and OUT pins.
That's what amplifiers do.
Now there's a ton of science behind how this works and amplifiers will never make much sense to you until you understand it... hence the link to All About Circuits. You need to start on lesson 1 and work your way through it.
(Note: I'm not affiliated with them in any way, they are simply an excellent resource).
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There are numerous events of various origin that do not carry signal characteristics, including AC components (ripple voltages). These fall under the vague nonspecific term "noise" and have a harmful impact on the signal. Far from all charges have appropriate properties to become a signal. The development of signals implies an intricate transformation involving nuclear rotation and many restrictions.
Yes. What's worse is that your posts have a wrong perspective.
Yes. What's worse is that your posts have a wrong perspective.
Hi and thanks scottjoplin and Douglas.
Great information - ok, I know I promised no more questions but this is directly related to the previous one.
It's a transistor which brings in channels both AC and DC together to send it through the circuitry, BUT is it a special specific type of transistor which sits at the 'beginning' (so to speak) of the circuit and allows the new conjoined AC/DC access to the rest of the circuitry - a sort of specific identifiable 'gateway' transistor ? - does it have a name ?
Thank you
Great information - ok, I know I promised no more questions but this is directly related to the previous one.
It's a transistor which brings in channels both AC and DC together to send it through the circuitry, BUT is it a special specific type of transistor which sits at the 'beginning' (so to speak) of the circuit and allows the new conjoined AC/DC access to the rest of the circuitry - a sort of specific identifiable 'gateway' transistor ? - does it have a name ?
Thank you
Well, no. Small signal transistor is a description, but you won't find those on websites for sale. Signals are small in current or voltage because tranducers that turn air pressure variation into electricity, or phonograph record grooves in to electricity, or CD pits into electricity are small. They tried big horns to collect a lot of sound energy in 1880-1910 to drive the recording needle directly, but those systems didn't make very accurate sound. Small transducers (microphones, pickups, photosensors) make small currents & voltages. So a small amount of electricity signal needs a low input capacitance transistor to avoid the signal being diminished in voltage by a large capacitance. Physically small transistor junctions have small capacitance. Such small signal transistors come in TO-92 packages or in older days, TO-18 packages. That is how you look them up at distributors. You can also find them under "low noise" transistors, although that description is kind of obsolete because all successful transistor manufacturers have eliminated all the impurities that used to float around in the air and damage transistor dies. Eliminating dirt increased yield as well as reduced noise, and higher yields lead to bigger profits, so the successful did that. So mostly manufacturers don't test for low noise as they did in the 1970's, but you get it anyway. One does have to be careful buying To92 transistors to buy "amplifier" transistors instead of "switching" transistors, as the layout of the mask is quite different for the two different uses.
Op amp IC's are another kind of low noise low input capacitance part that is quite popular now.
Some input circuits use jfet transistors, which are a special kind, see wikipedia, but as manufacturers don't sell a lot of them they are getting quite difficult to buy in the low noise low current categories. Leaded ones used by hobbiests are particularly becoming extinct. Jfet input op amps are more profitable and are quite cheap, really; useful for guitar pickups, ribbon mikes, and the like low current source transducers.
Such small signal transistors can't control enough current to drive speakers, only the smallest weakest ones. Low currents also can't drive long lines of high capacitance between say a mixer in the audience and an amplifier on stage. So there are medium size transistors used for the middle stage, called the "VAS" or voltage amplification stage. Then there are large high capacitance high output current transistors used for driving speakers actuators, or even batteries. Drivers come between the VAS & the output transistor that actually drives the speaker. Greg Erskine of AUS has produced tables of useful transistors of each kind available for sale. Driver Transistors
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No. You really need to acquire some basic knowledge of three-legged critters. They make up the vast majority of active elements you'll find (whether transistor, JFET, MOSFET or vacuum tube), and all they are is a variable conductance, controlled by either a voltage or current.
In a water analogy (which goes pretty far), they are a valve - and you'll find that in the UK, vacuum tubes are actually still being called "valves". The load resistor is equivalent to a pipe of a certain diameter. Now by controlling the valve, you can control the water level in between with relative ease. Turn it up, water goes down - turn it down, water goes up. Turn it it down all the way, and water goes to maximum. Turn it up all the way, and water level approaches its minimum, depending on how plentiful the supply is to begin with (load resistor value) and the valve's capacity (parasitic resistance etc.). The friction of the mechanism will even model input capacitance!
DC vs. AC is a purely artificial distinction for simplicity's sake. You are never, ever going to stumble across a 100% true blue DC voltage out of an ideal voltage source anywhere in your life. Real DC voltages get turned on and off, have some degree of ripple and noise on them and may drift over time.
You may want to think about what happens to the output if the input voltage does not change but the supply voltage does, and what this implies.
Ummm... I mean this in the most gentle way but NO that is simply isn't how it works. What you've got going right now is a profound misunderstanding. To fix this, you need to start from the beginning, with a good basis in electronic theory.
As I explained in my last post, DC is distributed throughout an amplifier as a means to provide power to the transistors, chips and other parts that handle and manage the audio signal... there is no magic gateway, it is all parts of the amplifier working together.
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Thank you again folks, for your very informative and comprehensive replies.
As Douglas suggests, a grounding in beginner electronics is obviously the way to go in order to make sense of the multiplicity of threads electrical stuff seems to throw up.
sgrossklass - the water analogy was excellent - really helped a lot
indianajoe - thank you for the tutorial on transistors, very helpful
Right, I'm going to get some studying done before I go any further.
Cheers and thanks again folks
As Douglas suggests, a grounding in beginner electronics is obviously the way to go in order to make sense of the multiplicity of threads electrical stuff seems to throw up.
sgrossklass - the water analogy was excellent - really helped a lot
indianajoe - thank you for the tutorial on transistors, very helpful
Right, I'm going to get some studying done before I go any further.
Cheers and thanks again folks
An "amplifier" takes a small interesting signal, and large boring power (say battery), to make a large interesting signal.
We use tricks to separate signal from power.
Apart from that process: we don't like batteries, we use wall lamp power, which is usually AC. Not the "interesting AC" of audio, but a boring hum. There is a process for turning wall power into steady DC as good as a battery.
We use tricks to separate signal from power.
Apart from that process: we don't like batteries, we use wall lamp power, which is usually AC. Not the "interesting AC" of audio, but a boring hum. There is a process for turning wall power into steady DC as good as a battery.
In the beginning there was nothing. And God said, “Let there be DC and let all the rest be AC, it is stupid to complicate things unnecessarily".
A signal is anything but periodic, fortunately, anything is representable with the periodic sine wave. Fourier used it to predict the whimsical heat propagation, which is not a signal, but it works fine for signals as well (adopting an imaginative interpretation of the results).
A signal is anything but periodic, fortunately, anything is representable with the periodic sine wave. Fourier used it to predict the whimsical heat propagation, which is not a signal, but it works fine for signals as well (adopting an imaginative interpretation of the results).
What's your definition of signal?
Many would say a square wave or sine wave is also a signal.
If you are being pedantic, no true sinewave exists. Most signals we take as sinewaves are better described as sine bursts.
Many would say a square wave or sine wave is also a signal.
If you are being pedantic, no true sinewave exists. Most signals we take as sinewaves are better described as sine bursts.
An electrical signal is a physical event conveying information (data), rather than noise. Mathematical waveforms are fictive representational entities that refer to nonexistent physical states and are clearly not signals.
With your forgiveness, I am going to disagree...
It's a good place to comiserate with other technical minds and yes, I've picked up a good chunk of new stuff since coming here.
But without a basis in credibly presented electronic theory forums like this one are also fertile ground for profound misunderstanding and unrealistic ideas. I'm guessing the levels of incompetence here are about on par with YouTube and a dozen other audio forums I checked out before settling here.
Now before we go getting bent out of shape (because someone surely will) I am not saying any one person here is totally incompetent. What I am saying is that even the best of us get it wrong sometimes.