So pot' or cap' which makes the biggest difference to tone..and erm water?

[iconic]

electricity as water, it's normally works as an analogy so help me out.

...following on from my other thread....simply changing the cap' on my bass didn't change the tone as far I could tell, I went from .047uf to .1uf on 500k pots.

hmm...

So, keeping [i][b]'electrickery[/b][/i]' as water to keep it simple, I'm assuming:-

1/ the tone pot' acts a 3 way (in and two outs) variable gate valve spilling some of the water (electrons from my pups) out the back of bass on the floor somewhere into the ether...?

2/ cap' acts a filter membrane at the exit of my pot gate valve....?

3/ so a 500k pot' is a more restrictive gate valve in the first place and the cap' is after the pot....?

4/ so if I fitted a 250k pot (i.e. bigger gate valve) the cap's effect would be proportional....bigger?


erm, appologies for the low level and somewhat painful assumptions here.


[i]My answer to such questions is always "water". Water flowing through pipes is a surprisingly accurate analogy for current flowing through wires. Current is how much water flows through a pipe. Voltage difference becomes the difference in water pressure. The pipes are supposed to lie flat, so that gravity plays no role.[/i]

[i]In such an analogy, a battery is a water pump, and a capacitor is a [b]rubber membrane[/b] which [b]completely blocks[/b] the pipe. DC is water flowing constantly in one direction through a pipe. AC is water flowing back and forth all the time.[/i]
[i]With this in mind, it should be obvious that a capacitor blocks DC: since the membrane can only stretch so far, water can't just keep on flowing in the same direction. There will be some flow while the membrane stretches (i.e. the capacitor charges), but at one point it becomes stretched enough to completely balance the water pressure, thus blocking any further flow.[/i]
[i]It also becomes obvious that a capacitor won't block AC completely, but it does depend on the membrane properties. If the membrane is sufficiently stretchy (high capacitance), it will pose no challenge to water flowing back and forth quickly. If the membrane is really rather stiff (e.g. a thin sheet of plastic), this corresponds to low capacitance, and if the water flows back and forth slowly, such flow will be blocked, but very high frequency oscillations will still make it through.[/i]

Edited June 29, 2013 by iconic

[iconic]

[i]just a thought. what effect would no cap have....I may had a dry joint for arguments sake?[/i]

[LukeFRC]

pickup loading is also important.
Ignore the cap for now.

Imagine the pickup is a reseviour, each pot is a pipe out of the dam into the river below.
If the pipe is wider more water can flow through, smaller less water.

The cap IMO isn't going to make as much effect as the resistance of the pots.
Mind you, your cable and the input stage of your amp are also active components in the tone of a passive bass.....

[Bloodaxe]

[quote name='iconic' timestamp='1372495388' post='2126355'][i]just a thought. what effect would no cap have....I may had a dry joint for arguments sake?[/i][/quote]

A dry joint would give a random value of anything up to ∞Ω, so could have the same effect as no cap, or (more likely) the same effect as BigΩ in series with the cap which is more akin to a switched 'varitone' circuit. That could result in it having little or no apparent effect.

Dry joints are dead easy to achieve with the new EuroSafe™ Lead-Free solder.

[icastle]

[quote name='Bloodaxe' timestamp='1372499180' post='2126413']
Dry joints are dead easy to achieve with the new EuroSafe™ Lead-Free solder.
[/quote]

Ah but it's safe.

You'd be surprised how many people spend their free time licking circuit boards.

[iconic]

ohh, lead free solder....I never knew that! My tone pot is doing something, these Westfield's are as a bright as button (great for slap!)...if the cap' wasn't 'in' the circuit I suppose I would still get the reduction in treble, just not so much?

PS thanks for taking out to read, and try and understand my poor understanding of electrons!

[Bloodaxe]

[quote name='iconic' timestamp='1372526041' post='2126855']
ohh, lead free solder....I never knew that! [/quote]
As well as not poisoning dolphins & trees, it has a noticeably higher melting point than 'proper' solder, so you might need to invest in a bigger iron (or get some decent solder from [url=http://www.finescale.org.uk/index.php?route=product/product&path=446_453_456&product_id=3686]here[/url])

[quote name='iconic' timestamp='1372526041' post='2126855']My tone pot is doing something, these Westfield's are as a bright as button (great for slap!)...if the cap' wasn't 'in' the circuit I suppose I would still get the reduction in treble, just not so much?[/quote]

If the cap's not 'in' it's not going to have any effect at all. The dry joint scenario is my present favourite as that could produce the effect you're getting.

It **ought** to be doing a [i]lot[/i]. I've had a hunt around trying to find a low-pass filter* calculator, & it looks as though a 0.1μF cap should affect frequencies over 100Hz or so (or the first octave A)**.

[i]Something[/i] is very wrong here. Any chance of a photo of your handiwork?

[quote name='iconic' timestamp='1372526041' post='2126855']PS thanks for taking out to read, and try and understand my poor understanding of electrons![/quote]

They're little scamps aren't they? The water analogy is a good ready reckoner for most simple instances, although in some cases it's important to remember that water comes out of the [u]earth[/u]. In the case of tone controls, it's possibly better to use fizzy water - the capacitor then becomes a 'bubble' valve that allows the fizzy stuff to escape leaving you with flat water. The bigger the cap, the more fizz it dumps.

P.

* technical term for a passive tone control, like wot we're discussing.
** that sounds terribly low, so I fully expect to be told I've got that properly wrong .

[iconic]

Many thanks for the help....i'll open the hood and check my handywork again...


.....fizzy water....excellent analogy!