From source to speakers , The journey ?

[Audio Al]

From source to speakers , The journey ?

I always like to try and understand things and without asking I am not sure on this one
So over to the one's who know

Take a source , say a turn table

Most cartridges I have seen have a four wire connecter from the arm wiring to the cartridge
And 2 wires from the TT to either the pre amp or phone stage ( RCA's )

The TT / pre and amp are all plugged into 230 v mains , but not the speakers

1st question are the other 2 wires a live and earth picked up inside the TT or something else ?

When the ( signal / music ) leaves the TT is it a voltage ? or a frequency ?

It goes into the amp that does what I assume is amplifying / making bigger , Then down the speaker cables to the speakers
Inside my B&O speakers is what is referred to as a X over units

The binding posts connect directly to the circuit board , one + and one -

This X over then somehow sorts out the music / ? and sends it to the relevant one of 3 speakers ( Driver tweeter and super tweeter ) ( as a voltage ? ) if it is a voltage I assume its very low ?
No earth on the speakers

Does this sound OK or am I getting it wrong ?

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Cheers :)

[dowser]

Each channel (left & right) has a signal and return (or, positive and negative) path. The 2 wires from you TT to amp are actually 2x2 wires. You'll also normally have a 5th wire from your TT, which is the earth wire, used to provide a return path connection between the TT and phono stage.

If an item is active it also has mains (or a battery) powering it - nominally 1 cable with 2 or 3 wires inside.

Note that some speakers are active too - electrostatics or active speakers also need mains power to function.

Speakers also have a return or negative connection - it can be argued that correct return path strategies make or break a system.

Does that help?

Richard

[Firebottle]

Hi Al, I'll try to keep this simple:

With any voltage (big or small) there is an associated current.
Think of a water tap and hose analogy; The water pressure is equivalent to the voltage in an electric circuit, whilst the water flow through the hose is equivalent to the current flow in an electric circuit.

The voltage is the 'push' and the current is the 'flow'. The amount of flow (current) is dependent on the amount of push (voltage) and the amount of resistance felt holding the water ( or electrons in the current 'flow') back.

For an audio signal it is usually referenced by the voltage as the current is very low.
The 4 wires from the cartridge are left+ and left-, and right+ and right-.
Once connected to the I/C to the pre amp the wires used are coaxial, that is an outer shield (also called common or ground) with an inner conductor carrying the signal. The left- and right- are connected to the outer shields of the two coaxial cables with the left+ and right+ connected to the inner conductors.

I'll follow on later with more.

[Firebottle]

As Richard said, if an item is active (it amplifies or provides some motive function) then a mains connection is needed to provide some power to be used in the function required.

For your first question, the live and neutral (return) of the mains wire into a T/T is to power the motor. There may or may not be an earth wire used as a protective/safety connection to the earth wiring in the plug/ring main of your house.
The wires from the cartridge are NOT connected to this earth, that's why there is an extra wire to 'earth' the metalwork of the arm/deck to shield against hum being picked up.

The signal from the cartridge is usually quoted as a signal of x millivolts, a millivolt being 1/1000 of a volt - a very small signal. [Not by radio receiver standards, but that's another story]. So it's a voltage but of varying frequency, i. e. the music.

The signal goes into an amp and as you guess it is made a LOT bigger.
By way of tradition the output of the amp is usually referenced by the power available, rather than the voltage. Power is voltage x current.
You also need to know what the resistance is this power is able to drive, that's why the resistance of the speakers is quoted.

As Richard said some speakers are active and need some energy from the mains, but most are not and use the power that comes from the amplifier.

The Xover in the speakers is just a filtering circuit to direct different parts of the music to the woofer/squawker/tweeter; The voltage levels can be quite high if the music is loud, typically 36 volts peak to peak is 20 watts in 8 ohm speakers.
Hope this clarifies things a little, ask away with any other questions.
:cool: Alan

[Audio Al]

OK

Many thanks for the reply's

I will need to read and try and understand this several time ,

It takes a while to sink into the old grey matter :D

[nat8808]

To simplify things for understanding, you should probably consider a cd player with a variable output into a power amp into some full range, single driver speakers.

That way you forget about all the wires from a TT and cartridge and you can forget about the cross-overs ("X-overs") in the speakers.

And in some way, it's very helpful to have a basic understanding of electricity too before you start.

I might also start with the speakers first as they are the easiest to understand and also are the reason an amplifier is needed.

In fact, in a non-realistic way (i.e. not how commercial hifi has developed), you don't even need a pre-amp or an amplifier at all.

So, for the most simplistic understanding, imagine instead a CD player that is wired directly to some speakers like those found in headphones.

Take it even further and think of a crystal radio set whereby the electromagnetic radio-wave is enough to drive the speaker itself!

Confused? You will be... Doo doodo do doo dodododo, doo doodo do doo dodododo.. (does anyone remember the US sitcom "Soap" ?)

[nat8808]

Here's a lot more rambling for you - not easy to write without probably being confusing but I've tried:

A speaker is just a coil of wire in a magnetic field (the field provided by a large magnet) with the coil attached to a cone of paper (or whatever). If you pass an electrical current through a wire that sits in a magnetic field, it moves! (the current sets up it's own magnetic field and the two interact, causing a force on the wire).

If you want the wire to then move in the opposite direction, you reverse the current and it moves in the opposite direction.

With a speaker, passing this current through the coil of wire will make the cone go out and then, when you reverse the current, it will move in.

Sound is passed through the air to our ears by creating lots of pressure pockets by things squashing or expanding the air by little or large amounts by their surfaces vibrating back and forth. A speaker cone does the same thing - it moves in and out a lot to reproduce the wave of pressure pockets like the surface of a real thing would, the body of a violin, a piano etc.

If we keep reversing the current through the speaker coil, the speaker will keep going in and out. If we speed that reversing up, we get to a point where we hear notes. The number of times we reverse that current per second is called the frequency of the signal (the signal being this current we're passing to the speaker). So now we can play basic notes through the speaker.

A little electricity aside here: to make a current pass through a wire, you need to give it reason to travel and we call that reason 'voltage'. You can also think of voltage as being like an electro-magnetic attracting force. Imagine a hoover tube.. the bits of dust are bits of the current (in physics called 'electrical charge' - the actual electrons don't actually move that much along the wire.. won't get into that) and the faster they move being like a higher current, they have more energy. As you turn on the hoover, the dust is sucked along the tube - same as applying a voltage across the wire so the current moves through it. Set the hoover to 'blow' and the dust travels the other way - this is like the voltage on a wire being reversed. The higher the setting on the hoover in either suck or blow mode, the faster the dust will travel in either direction - same with the wire; the higher the voltage across the wire, the more current flows in both 'suck' or 'blow' mode. End of the 'Electricity aside'.

To get a good sound out of the speaker, one that sounds real, how the cone moves needs to very complex, moving at different frequencies and at different speeds and by different amounts. To do this, the current through the wire needs to change in complex ways. You change the current by changing the voltage across the coil wire - you vary the size of the voltage and you change the frequency of the reversing of the voltage too. It's all happening pretty fast and those changes superimposing upon each other so you end up with what looks like the very same waveform in voltage terms as you see in pictures as a sound wave all over the place, on computer screens etc etc.

So, this changing voltage/current is the audio signal being fed to your speakers. It is essentially the same signal that is coming out of your CD player. If you had speakers that didn't need much current to make them work or much voltage change to get that current to move through the coil well enough (probably very small speakers, like those in headphones) you could feasibily just plug them straight into your Cd player. Job done!

In the real world, due to the standard and past practices of hifi and making things work together - kind of a loose standardisation - and wanting much higher loudness volumes, the signal out of the CD player isn't strong enough (high enough voltage or able to give enough current). This is where the amplifier comes in. The amplifier, on a basic level, sees the signal coming in, takes some electricity from the mains and adds this new electricity to make the signal bigger and stronger so that it can drive the speakers ok.

To excerise some control over volume, you can change the size of the signal coming from the CD player into the amp. Some Cd players will have a variable output and some won't. Therefore we mostly use a pre-amp that in its simplest form will just block some of that signal to make it smaller and therefore reduce the volume. If we want to conveniently switch from source to source, it has a selectable inputs. This is what a passive pre-amp is - it doesn't need any power from the mains as it is just using resistors etc to change the signal size from the CD player. Some passive pre-amps will also convert energy from the current in the signal to make higher voltages and so actually amplify the signal a little in a certain way - still passive but using transformers and able to provide some amplification. Some power amplifiers need an input signal with stronger current to work at its best and so a pre-amp might also need to amplify the CD player signal fully (in both current and voltage) before it has even reached the amp. Working in the same way as the amplifier but on a smaller scale, the pre-amp takes some electricity from the mains to boost the signal in both voltage and current. This is an 'active' pre-amp. Matching the right type of pre-amp with a given amp (and speakers to the amp) is what the hifi game is all about to get the best sound.

So... on a basic level, you can think of the signal as travelling from the cd player into the pre-amp where you can control the amount of signal passing through. Then the pre-amp may add a little to the signal, amplify it a bit before it reaches the power amp. The power amp then amplifies the signal again to provide enough current and voltage to the speakers to make the cone move in and out enough for a given loudness.

Whenever that basic model fails or causes confusion, you have to realise that in reality the signal is pretty much instantly everywhere in every part of the signal chain all at once, the voltages being set up instantly (or at least at the speed of light) and responding instantly all over to the environment and changes in each component and connecting wires etc etc (I think the simple linear view of the passage of a signal is what leads many people to rule out cables making a difference out of hand for example). Obviously good designs of equipment seek to minimise these effects and manufacturers can have more control when they design both the pre-amp and power amp together.

Cross-overs: all you need to know is that the crossover splits the signal and allows one lot of frequencies to pass to one driver and another set of frequencies to another driver. This is done using electromagnetical resonant properties of components.. Think of an old car - drive at low speed/engine speed and some internal pannels will vibrate, drive at a higher speed/engine speed and other panels with vibrate at a higher rate. They vibrate differently due to how they are damped, what they're made of, how they're mounted etc. Same with the components in a crossover but with electromagnetism - one combo of components will dampen (stop) some frequency of signal coming through at all and another set will block out a different set of frequencies and so allowing different signals to pass .

It's all physics at the end of the day.

[Audio Al]

Thank you Nat

I now understand , you have simplified it to a point that I can understand

Never given the opportunity to do physics at school as it was not on the agenda ;)

[Barry]

Excellent post Nat!

So good in fact, it is a suitable candidate for inclusion in The Knowledge, if you are willing.

PM me if you are interested.

Regards