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i've just realised i don't know how a bass guitar works!?!

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Yeah i know....a coil around a magnet etc and i end up with a voltage at my jackplug socket....so my bass is a voltage generator.

i know its an AC voltage millivolts but can go to to volts.

but.....does a low voltage give the low notes and the higher voltage the higher tones or is it more a function of current?

If i had an AC voltage generator and plugged it into my amp I should get a bass tone....knowing me an electric shock!....and would the wood around my voltage generator...no, I'm not going there!

Just asking.

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A vibrating piece of metal (string) within a magnetic field (created by the pickup magnets) can be used to induce a current. The voltage that you create governs how loud the output signal is - when you're tickling the strings you'll get a teeny weenyvoltage to the output, when you're really digging in then the voltage will be significantly greater (but still only millivolts).

This is worth a watch - it's a guitar PUP, but the science stuff is exactly the same (except better) for a bass. :)

[media]http://youtu.be/wKS0ZWCHI4g[/media]

Edited by paul_5

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[quote name='iconic' timestamp='1392541139' post='2369742']
but.....does a low voltage give the low notes and the higher voltage the higher tones or is it more a function of current?

[/quote]
Neither. It's a function of the frequency of the AC oscillations created by the string moving through a magnetic field.

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[quote name='iconic' timestamp='1392541139' post='2369742']
Yeah i know....a coil around a magnet etc and i end up with a voltage at my jackplug socket....so my bass is a voltage generator.

i know its an AC voltage millivolts but can go to to volts.

but.....does a low voltage give the low notes and the higher voltage the higher tones or is it more a function of current?

If i had an AC voltage generator and plugged it into my amp I should get a bass tone....knowing me an electric shock!....and would the wood around my voltage generator...no, I'm not going there!

Just asking.
[/quote] the voltage is the volume.
a note is a frequency, your guitar string makes an acoustic you can hear by vibrating at that frequency. it vibrates over the pickup inducing an AC current in it... the way the AC alternates matches those frequencies....

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so if you had your bass amp and plugged it into the mains AC power, in the short time before youyou were electrocuted to death and your amp blew up burning your house down you would hear the frequency of the power...
which in the uk is 50Hz
if you went to the states the voltage would half and the frequency would be 60Hz. You would still die horribly, with your amp exploding and burning your house down though so don't try it.

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[quote name='LukeFRC' timestamp='1392544281' post='2369785']
so if you had your bass amp and plugged it into the mains AC power, in the short time before youyou were electrocuted to death and your amp blew up burning your house down you would hear the frequency of the power...
which in the uk is 50Hz
if you went to the states the voltage would half and the frequency would be 60Hz. You would still die horribly, with your amp exploding and burning your house down though so don't try it.
[/quote]

hmm good point!

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So if I understand this correctly

1/ The volume would be a function of the voltage generated..,.,and

2/ The frequency of the sound (my interest here) is a function of the frequency of the AC voltage generated...which is a function of

3/ The frequency of the string oscillating when struck?

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[quote name='paul_5' timestamp='1392545589' post='2369803']
A bit like this…

[media]http://youtu.be/_vp9WfBuxDo[/media]
[/quote]

is that a WishBass of some sort ;)

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[quote name='iconic' timestamp='1392546931' post='2369822']
is that a WishBass of some sort ;)
[/quote]I can say i have never had a wish for it

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[quote name='Grangur' timestamp='1392549218' post='2369857']
The amp outputs an AC signal to the bass. This signal passes through the coils of the pickup and the circuit is completed with the signal going back to the amp.
[/quote]

Wrong. The bass pick-up is a signal generator. The signal flows from the bass to the amp. The amp sends nothing to bass.

The jack socket on the bass is an output socket. End of.

Edited by obbm

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[quote name='Grangur' timestamp='1392549721' post='2369865']
How does it do that?
[/quote]

How does what do what?

If you take the trouble to Google there is a huge resource about electricity and magnetism on the Internet. Try "GCSE Electricity and Magnetism" or "How guitar pick-ups work physics".

Edited by obbm

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I believe that the tone or timbre of a particular note originates from the sub harmonic frequencies?

Otherwise a piano playing a middle C would sound just like any other instrument playing the same note.

I'd love to analyse the different sub harmonics that different basses produce in order to establish what different woods/bridges/nuts do to the tone vs the human ear that can be preprogrammed by expectations.

Peter

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[quote name='iconic' timestamp='1392546740' post='2369820']
So if I understand this correctly

1/ The volume would be a function of the voltage generated..,.,and

2/ The frequency of the sound (my interest here) is a function of the frequency of the AC voltage generated...which is a function of

3/ The frequency of the string oscillating when struck?
[/quote]

Listen to your bass. It makes the same tone whether it is plugged in or not, it gets louder if you hit it harder, it is quieter if you pluck it softly, the electricity involved does nothing for the frequency (apart from any interference but that is fairly irrelevant).
The pickup is a coil of wire in a magnetic field. when the string of your bass oscillates in the magnetic fields it affects that field and as a result generates a small electrical charge in the coil of wire. The bigger the change in the field (ie, the further the string moves), the higher the voltage of that charge.
The amplifier takes that voltage and amplifies it, as well as providing enough current to move a speaker (which it does by exactly the opposite procedure of generating a voltage in a coil which causes it to move in a magnetic field.

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[quote name='GreeneKing' timestamp='1392554840' post='2369936']
I believe that the tone or timbre of a particular note originates from the sub harmonic frequencies?
[/quote]

The harmonic frequencies, not sub harmonics, there are a whole load of harmonic frequencies which change the characterisation of the sound, so a smooth tone would have a lot more even harmonics like a flute, whereas something like a brass instrument would have more odd harmonics.
Although there is a difference by different woods it is much smaller than you would think, and absolutely dwarfed by the perceived tone change achieved by spending a lot more money on the bass!

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[quote name='Woodinblack' timestamp='1392557886' post='2369977']


The harmonic frequencies, not sub harmonics, there are a whole load of harmonic frequencies which change the characterisation of the sound, so a smooth tone would have a lot more even harmonics like a flute, whereas something like a brass instrument would have more odd harmonics.
Although there is a difference by different woods it is much smaller than you would think, and absolutely dwarfed by the perceived tone change achieved by spending a lot more money on the bass!
[/quote]

Absolutely. I did mean harmonics not sub harmonics. It's been a lot of years since I explored waves at Uni :)

Peter

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[quote name='Woodinblack' timestamp='1392557523' post='2369967']
Listen to your bass. It makes the same tone whether it is plugged in or not, it gets louder if you hit it harder, it is quieter if you pluck it softly, the electricity involved does nothing for the frequency (apart from any interference but that is fairly irrelevant).
The pickup is a coil of wire in a magnetic field. when the string of your bass oscillates in the magnetic fields it affects that field and as a result generates a small electrical charge in the coil of wire. The bigger the change in the field (ie, the further the string moves), the higher the voltage of that charge.
The amplifier takes that voltage and amplifies it, as well as providing enough current to move a speaker (which it does by exactly the opposite procedure of generating a voltage in a coil which causes it to move in a magnetic field.
[/quote]

I could of worded my question better....my question is how the different sound frequencies are related to the electricity derived by the pick-up...I've re-read that it is still clear as mud! ;)

if I understand correctly are you saying the pick-up is simply a microphone?

Edited by iconic

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[quote name='iconic' timestamp='1392566166' post='2370071']
if I understand correctly are you saying the pick-up is simply a microphone?
[/quote]

As far as I know yes it is simply a microphone of sorts, you can demonstrate this by singing or shouting into a guitar or bass pickup when the instrument is plugged into an amplifier; it's not a great sound but you will hear your voice being amplified.

The guitarist David Torn utilises this by playing recorded sounds into his pickups with a handheld recorder & then looping & modifying the outputted sounds with his pedal board.

Edited by RhysP

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[quote name='iconic' timestamp='1392566166' post='2370071']
I could of worded my question better....my question is how the different sound frequencies are related to the electricity derived by the pick-up...I've re-read that it is still clear as mud! ;)
[/quote]

I am not quite sure what you mean. The frequency of the string movement obviously changes the pitch of the note, and that the pickup replicates that to come out of the amplifier, but apart from the fact that amplifiers and pickups have a slightly different response to different frequencies, there is little difference to what that frequency is.
Generally speaking a bigger string will have a higher output than a smaller string, but that isn't for any electrical reason, it is because the string has more mass so will move further.


[quote name='iconic' timestamp='1392566166' post='2370071']
if I understand correctly are you saying the pick-up is simply a microphone?
[/quote]

The pickup is picking up the changes in the magnetic field you get because a large chunk of metal is moving through it. It isn't quite a microphone because for a microphone you need something to detect the changes in air pressure (such as a diaphragm) and then convert that movement to a change in a coil moving through the magnetic field. Once you have that it works the same.

There is another type of microphone that works like a piezo pickup but don't want to muddy the waters with those!

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[quote name='RhysP' timestamp='1392566892' post='2370081']
As far as I know yes it is simply a microphone of sorts, you can demonstrate this by singing or shouting into a guitar or bass pickup when the instrument is plugged into an amplifier; it's not a great sound but you will hear your voice being amplified.[/quote]

If you do hear this, replace your pickups with ones that have been potted properly. The sound of your voice through a pickup is due to the vibration of the coil over the magnet because the pickup hasn't been sealed. This will happen on cheap pickups (and older ones where the potting has rotted out), but shouldn't happen on anything that costs over £5!


[quote name='RhysP' timestamp='1392566892' post='2370081']
The guitarist David Torn utilises this by playing recorded sounds into his pickups with a handheld recorder & then looping & modifying the outputted sounds with his pedal board.
[/quote]

Ah, that is different. you will be able to hear recorded sound as the pickup can detect the magnetic variations that power the speaker in a recorder.

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[quote name='Woodinblack' timestamp='1392568754' post='2370116']
If you do hear this, replace your pickups with ones that have been potted properly. The sound of your voice through a pickup is due to the vibration of the coil over the magnet because the pickup hasn't been sealed. This will happen on cheap pickups (and older ones where the potting has rotted out), but shouldn't happen on anything that costs over £5!
[/quote]

. . . Or perhaps the voice vibrating the strings?


[quote name='Woodinblack' timestamp='1392568754' post='2370116']
Ah, that is different. you will be able to hear recorded sound as the pickup can detect the magnetic variations that power the speaker in a recorder.
[/quote]

That's similar to the way the TC Electronic toneprint thing works - using a smartphone to send toneprint data to their amps via an audio signal sent through the guitar pickup.

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It's said that any sufficiently advanced technology is indistinguishable from magic, and having skimmed this thread I'm now quite content to accept that the incompetence that I put into my bass gets turned into music by the fairies. :)

Jon.

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[quote name='Bassassin' timestamp='1392595898' post='2370556']
[u]It's said that any sufficiently advanced technology is indistinguishable from magic[/u], and having skimmed this thread I'm now quite content to accept that the incompetence that I put into my bass gets turned into music by the fairies. :)

Jon.
[/quote]

First said by Arthur C. Clarke, and thus known as Clarke's Law.

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