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On a passive Jazz bass, the controls are volume / volume / tone. Obviously the tone pot has a capacitor on it.

Now in an active with volume / balance / treble / bass I would assume each of the treble and bass would have caps of different values. Am I correct in this logic?
 

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It's always something...

james on bass said:
On a passive Jazz bass, the controls are volume / volume / tone. Obviously the tone pot has a capacitor on it.

Now in an active with volume / balance / treble / bass I would assume each of the treble and bass would have caps of different values. Am I correct in this logic?
Not exactly, James.

With a passive control in a guitar, we have a very simple circuit for the tone pot. It has a cap in series with a pot. This is a treble cut circuit. Caps let through high freqencies better than lower ones. To an AC audio signal they actually look like an AC resistor and to techies this figure is called "reactance". This circuit doesn't cut a "notch" but rather starts leaking at a certain frequency and as you go higher it gets better and better at it! That's why we call it a treble "cut".

One cap and a pot give a kinda slow "slope" to the treble cut. How big a cap we use determines how low a "resistance" we have at a certain frequency. The pot lets us control how much total resistance we have in the path with the cap to ground. So the circuit leaks treble to ground and we can play with the cap and pot values to get something useful to the ear.

An active bass has a preamp circuit added with powered amplifying devices added to boost the signal. There are a whole bunch of ways you can combine caps and stuff in such circuits and things tend to be more complicated than just a simple cap bypassing to ground. However, you're correct that the portion of the circuit dealing with the lower frequencies will likely have bigger value caps than the treble portion. You will NOT see a big cap through a pot to ground used for a bass control! This doesn't work. It would simply start leaking at rather low frequencies and even better at the treble ones too! It would pretty well zot EVERYTHING out...

Hope this is useful to your question...
 

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Thanks Bill - it does make sense - sort of:smile: . I'm pretty much clueless with too much technology. I've been enjoying modding my basses - swapping out for better pots, changing the cap values a bit etc...
As soon as I started reading your response, I remembered what the inside cavity looks like on past active basses I've owned- more like a mini-circuit board attached to the pots than a nice simple passive bass. If I get the bass I'm thinking of, I may just swap out the cheap pots for nicer ones and leave it at that. I don't want to mess around with circuits.

thanks for your help.
 
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