Highpass filter? (G+L style)

[pandathe3]

Hi there,

I'm currently designing a passive circuit that you could use as a direct replacement for any cheaper Jazz's/Stingray's to put in my basses.

I like the idea of have both a lowpass filter and highpass filter like the G&L basses. Unfortunately ive never spotted a G&L bass in my area and had a go playing one. As i understand, the Highpass filter, is just a 1meg pot with a .0022uf cap.

So if i were to do this, what affect would the 1meg pot have on my sound?

Cheers!

[metron]

http://en.wikipedia.org/wiki/RC_circuit

Both the resistor and capacitor values determine the cutoff point of your filter so they work together. It's hard to say what the real effect of raising or lowering the 1 Meg resistor value is on sound without first calculating the filter cutoff then substituting different values into the equations. A lower cutoff point on a highpass filter would result in more low end with the filter on and vice versa for a higher cutoff. A lower cutoff on a lowpass filter would result in less treble with the filter on and vice versa for a higher cutoff.

[SGD Lutherie]

The 1M treble pot is in SERIES with your signal, so it does not affect the tone at all. What's going on is the circuit has the signal going through the .0022µF cap, which removes the low end. The 1M pot bypasses the cap to give the full low end. The reason it is so large is so that it doesn't interfere with the cap, since they are in parallel. So it's not part of a RC filter.

Here's the schematic.

[bassbenj]

Originally Posted by pandathe3

Hi there,

I'm currently designing a passive circuit that you could use as a direct replacement for any cheaper Jazz's/Stingray's to put in my basses.

I like the idea of have both a lowpass filter and highpass filter like the G&L basses. Unfortunately ive never spotted a G&L bass in my area and had a go playing one. As i understand, the Highpass filter, is just a 1meg pot with a .0022uf cap.

So if i were to do this, what affect would the 1meg pot have on my sound?

Cheers!

Go see what SGD has to say. That pretty much explains it. Passive bass-treble knobs are a nifty thing to have (I have a couple of G&Ls). The treble knob is basically your standard passive tone control which cuts highs. The "bass" control as explained only can cut the deep lows. This is the way passive controls work. They can't "boost" any signals.

So a typical way you use these controls is to set the controls mid range and go to your amp and boost the highs and lows back up to compensate. This then gives you some boost and cut over the range of the passive controls. But be aware that this trick does not give you the range of EQ that an active circuit typically gives. Nevertheless it is highly useful and especially nice in that it's on a passive bass.

But the "boost" trick isn't useful if you are playing with other basses too. Then you'd have to re-EQ each bass. So often I just leave the passive "bass" control to pass all lows and only seldom use it to cut lows. If you build it, you'll see what I mean. But it's still nice to have it there to have more control over your tone.

[lowfreqgeek]

Originally Posted by SGD Lutherie

The 1M treble pot is in SERIES with your signal, so it does not affect the tone at all. What's going on is the circuit has the signal going through the .0022µF cap, which removes the low end. The 1M pot bypasses the cap to give the full low end. The reason it is so large is so that it doesn't interfere with the cap, since they are in parallel. So it's not part of a RC filter.

Here's the schematic.

FYI, the RC filter is created by the 0.0022uF cap and the 250k volume pot. The 1Meg pot acts as a bypass as SGD said. If you don't use a 250k load (the volume pot wired the exact way it is in the G&L schematic), or you change the capacitor value, the filter response will change.

The filter response is tuned for the G&L MFD pickup and may require some significant tweaking to work well with anything else. The corner frequency of the G&L circuit is about 290Hz or so - everything below that is cut by some amount, depending on where the 1Meg pot is set.

Give it a try and see what think. Tweak to taste!