Question about frequency response of HB pups...

[salvarsan]

In this case, the drive coil is a 16ohm round device (diameter: 15mm) and the "signal generator" is just... the headphones output of a SBLive soundcard (!).

Magnificent!

Cheap is good.

This means you could make a 16 ohm driver from a PAF bobbin and 20 winds of #42.

[freefrog]

This is probably a stupid question and overly obvious - but are you doing this through a typical guitar wiring setup? 500k pots and tone caps and all of that? Won't capacitances from there cause this sort of thing...?

Your question is probably less stupid than my own questions, tests and methods! !-))

Yes, I do these tests with all the guitar harness around the tested pickups.
If I test a pickup alone, I obtain a higher and sharper resonant peak, located higher in the audio spectrum, but the "overall shape" of the curve remains the same.

[Mike Sulzer]

In this case, the drive coil is a 16ohm round device (diameter: 15mm) and the "signal generator" is just... the headphones output of a SBLive soundcard (!).

With the rising frequency response explained by the 100 pf capacitor, then the current through the drive coil must be decreasing with frequency to compensate for the increase of dB/dt with frequency. Presumably then you are using a ferromagnetic core in this coil that makes it inductive across the whole frequency range?

[freefrog]

With the rising frequency response explained by the 100 pf capacitor, then the current through the drive coil must be decreasing with frequency to compensate for the increase of dB/dt with frequency. Presumably then you are using a ferromagnetic core in this coil that makes it inductive across the whole frequency range?

In the (already old) examples above, it was a simple "air coil": it was supposed to work, since the real tests done with it on real single coils matched exactly their 5Spice analysis counterparts.

As mentioned above, anyway, it's only with a few humbuckers that I notice the highrange roll off which questions me (highrange roll off that I can see on a spectrum analyzer when I play these pickups through a full range preamp). Most of the pickups that I've tested exhibit either an even decay beyond their resonant frequency, either a secondary resonant peak without much phase cancellation. Hence the idea that the phenomenon mentioned here probably comes from the PU's themselves rather than from my testing gear.
now, if I'm wrong and/or if you have another explanation, I'll be happy to learn something. :-)

[David King]

So is the rise a 6dB per octave slope? That's what it looks like to me. The drop looks about the same so something is changing pretty dramatically in the system at the apex. I guess that's why folks have referred to this as a band-pass circuit.