Can a passive high pass filter work with active pickups?

[TSE]

Like the one Artie showed us or the one on metalguitarist.org forum? Provided I get the component values correct.

[big kurka]

I've read that it can be done. Thats all that someone said in a different forum. They didn't say if you had to use different pots. I wouldn't imagine you don't need different pot values though.

[jtougas]

I think the Blackouts use a 25k pot (for example).

Past that, I think the schematics normal.

[Funkfingers]

In theory, a HPF can process any audio signal. On an electric guitar, a passive bass cut filter would work regardless of whether the pickups are powered or not. For an active filtering device, it is a question of supplying the correct voltage.

[Maynardo]

Like the one Artie showed us or the one on metalguitarist.org forum? Provided I get the component values correct.

link please

[TSE]

http://www.metalguitarist.org/forum/...-bass-cut.html

[uOpt]

It will not work, at least not unmodified.

The problem is that the pickup doesn't just deliver a signal. The pickup is a second order low pass filter with resonance peak in itself, and the parameters for the pickup's own filter are determined by the capacitance (add cable's capacitance, inductance and resistance (take rig input impedance into account) of the pickup.

But capacitance, inductance and resistance are put on the wire without anything "protecting" it. Adding any kind of electronic component without an impedance changer after the pickup modifies the pickup's own filter parameters. That's e.g. why the cable adds it's capacitance to the pickup's capacitance and changes the sound significantly, when the cable in itself wouldn't do much.

That doesn't mean you can't remove bass from a passive pickup, but you will need an entirely new circuit that modifies the pickup's values. You cannot use a regularly designed HPF without an impedance changer.

[Bfeeney]

I think the Blackouts use a 25k pot (for example).

They are, EMGs are 25k too.

[RayBarbeeMusic]

Of course it would work, RC networks will work as high or low pass filters. What you'd need to determine is the appropriate values for R and C.

Since actives use 1/5 to 1/20 the value of normal pots (R) depending on manufacturer, I'd go with that as a starting point for the pot.

G&L has been using what was described in that article as the "B" in their PTB system for decades (PTB = Passive Treble/Bass). With passive pickups they use a 1M control and a .0022uf cap. So if you are using EMGs or other actives that require 25k pots, try a 50k or 100k pot for your passive bass control; if you are using actives that requrie 100k pots, try a 100k or 250k pot.

If you look online there are all kinds of RC network calculators that can give you an idea of where to start on values (assuming you know the impedance of the source, or can at least guess).

Edit: I did some calculations assuming about a 1K output impedance on the actives, and it really isn't that sensitive to it, 1M/.0022uf should work fine. If you lower the value of the pot, you'll need to increase the size of the cap. Easiest thing is start with a common, readily available pot value, get some caps and aligator clips and determine which cap you like best.

[uOpt]

EMGs and Duncan actives are a different matter. They have an impedance changer (the preamp). After that you can use a perfectly regular HPF. The HPF values cannot influence the pickup's own LPF anymore.

You can do the same by using the little preamp SD sells you for passives.

[TSE]

The pups are blackouts phase two. They need to be tighter on 7 string guitars