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Passive basses and the volume control, an explanation (science warning)

#41
About the tone control before the volume control (no pics yet):

At full volume, there is no difference between having the tone control before, or after the volume control, since the volume pot turns into a parallel resistance. If volume is turned down and the tone pot is after the volume control, we get the shelving filter behavior shown previously. If the volume control is after the tone control, the tone control continues acting like a standard high roll-off. So if you are looking for minimum interaction between the controls in a single pickup setup, place your tone control before a volume control wired as a voltage divider.
 
#44
l0calh05t said:
About the tone control before the volume control (no pics yet):

At full volume, there is no difference between having the tone control before, or after the volume control, since the volume pot turns into a parallel resistance. If volume is turned down and the tone pot is after the volume control, we get the shelving filter behavior shown previously. If the volume control is after the tone control, the tone control continues acting like a standard high roll-off. So if you are looking for minimum interaction between the controls in a single pickup setup, place your tone control before a volume control wired as a voltage divider.
Click to expand...

This reflects my own observations.

I wonder how many people know the significance of your signature? :D
 
#51
Al Heeley said:
Can you offer any insight into wiring a passive mid-cut control to a bass circuit?
Click to expand...

Cap with an inductor (LC network). That's also how an Varitone circuit works.

You would wire them up as on a tone control. The Gibson Ripper had a mid cut control like this.

Here's the Ripper (L-9S) schematic. They used a .1 cap and a 1.5H inductor.

Craig Anderton used an audio transformer for the inductor. He stated it was 5 - 6H. You can use half of an audio transformer, like the one from RadioShack or Mouser part # 42TM-019. You can experiment with different cap values too.
 

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#52
Yup, that's pretty much what I meant. Using an audio transformer is a good idea, as large inductors are otherwise quite difficult to find.

You can calculate the center frequency of this mid cut like so:
1/(2*pi*sqrt(L*C))

So for the Ripper that would be ~410 Hz.
 
#54
Al Heeley said:
Thanks guys - so just cap and inductor in series from the tone pot sweep to earth?
Just one thing - what exactly is an audio transformer? Is that a US term for something I can get hold of in the UK?
Click to expand...

An audio transformer is a transformer designed for audio (low distortion and mostly linear over 20-20kHz and designed for low power, so no tube amp output transformers :p Those wouldn't fit in the control cavity anyways)

Here would be a cheaper one (not particularly good, but should suffice for this purpose): Invalid Link Removed
 

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