Passive electronics: Mid cut

[mongo2]

Originally Posted by fullrangebass

Villex offers up to 12dB passive boost through his PRTB line of products (Passive Rotary Tone Booster)

Passive boost?

[fullrangebass]

Yes indeed!!! 12dB boost

[DerHoggz]

This is really interesting.

Would ths be possible to apply to low frequencies? That would be sick.

[SGD Lutherie]

Originally Posted by mongo2

Passive boost?

Yeah, I believe he's using a step-up transformer for the boost.

[mongo2]

Originally Posted by SGD Lutherie

Yeah, I believe he's using a step-up transformer for the boost.

Hmmmm, interesting.

[SGD Lutherie]

Originally Posted by mongo2

Hmmmm, interesting.

I'm just speculating.... Villex is the guy who invented the Lace Transsensor and Alumitone pickups, so it only makes sense that he's doing something similar.

[fullrangebass]

Originally Posted by DerHoggz

This is really interesting.

Would ths be possible to apply to low frequencies? That would be sick.

He is applying it to the low frequencies and the result is really impressive esp with the PRTB II

[southernrocker]

Originally Posted by 3506string

http://www.guitar-mod.com/rg_passive.html

I have the push-pull mid cut in my jazz. It's not incrediblely noticeable, but it takes the harshness out of slap.

[fullrangebass]

Originally Posted by pickles

The villex system has this, I didn't really like the way it sounded. The mid control took some highs along with it so it wasn't useful for getting any kind of sharp mid scooped sound.

By using the PRTB and the Mid-control results in sharp mid scooped sound

[ac3320]

Old thread, but do you guys know if it is possible to have a pot that provides passive treble cut like a normal tone pot, and then when turned the opposite direction, a passive mid cut?

Dingwall offers this functionality on their Super P basses (passive models), and they call it "Tone-Fusion." They have a center detent, and counter-clockwise is for passive tone cut (as to be expected), while clockwise rotation of the knob leads to the passive mid cut.

Rothstein essentially offers the same functionality as Dingwall, except that they are using a push-pull pot as a selection for treble vs mid cut, and the knob only rotates counter-clockwise. Not a big deal, but in my experience, push-pull pots have a different feel compared to conventional pots, and generally suck at life as well. I'd like to avoid said sucking at life if I can.

Any ideas?

[eukatheude]

Couldn't you just use a specific cap value? If i understood this thing right, with a 800nf cap on a 250k pot you should cut roughly at 800hz. Or i got this completely wrong?

[Crater]

Originally Posted by eukatheude

Couldn't you just use a specific cap value? If i understood this thing right, with a 800nf cap on a 250k pot you should cut roughly at 800hz. Or i got this completely wrong?

But a standard passive tone control doesn't just cut those frequencies, it's cuts everything higher too. The higher the frequency, the more dB is removed, the 800 Hz (or whatever) is just the "knee" frequency, I believe that's where the filter is -6dB crossover point. Frequencies higher than 800Hz are cut even more.

[abemo]

You might be able to use that cap if you also bypassed the mid cut pot with a smaller cap to let the highs through unimpeded, but I believe SGD had a fairly detailed description of the proper way to do this with a cap and an inductor.

[SGD Lutherie]

Originally Posted by eukatheude

Couldn't you just use a specific cap value? If i understood this thing right, with a 800nf cap on a 250k pot you should cut roughly at 800hz. Or i got this completely wrong?

The frequency that the tone control cuts at is also determined by the impedance of the pickup. Passive tone controls are not really RC networks like those in the link. It's more of a resonant low pass filter and uses the pickup as part of the circuit.

So the higher the impedance of the pickup, the more affect the cap has on the tone. This is the original series active EMGs use .1µF tone caps, and still the control does very little.

[eukatheude]

So i should take into account the pickup impedance by just adding it to the pup impedance?