DiMarzio HS-3

[surgo]

I bought these for a project, didn't end up using them, and am selling them. Before I do, I figured I'd measure their frequency responses to add to the collective knowledge. These were measured using Ken Wilmott's "Integrator" device, through the RightMark Audio Analysis software and my audio interface. They aren't hooked up in a guitar circuit, instead they were measured with the Integrator's test circuit (which provides the capacitance and impedance).

First plot is the response from a sine sweep, the second is from a multi-tone test. They're, to me at least, impressively flat up until their resonant peak.

edit: these were wired in series (not sure there's a point to wiring these stacked hum-cancelers in parallel).








Hope that information helps somebody.

[stratotarts]

Just FYI, a multi tone test is meaningless for pickup measurements. It's designed to analyze intermodulation distortion as the result of non-linearity in the response. If the tests are conducted with correct signal levels, there should be no measurable distortion or non-linearity. The sine sweep is the appropriate method in this case.

[aquin43]

You can use multitone on a linear system to get a fast readout of frequency response at the multitone points. Ultimately you can use a noiselike signal such as MLS (minimum length sequence) to get a fast readout with a fine frequency resolution. The limitation of the method is that, because the overall signal level is limited by the hardware, the more frequencies you use in the multitone signal, the lower the effective level of each tone. You can then run into difficulties with hum interference. The given curve shows no evidence of that being a problem in this case.

The curves do show a problem with low frequency roll off in the measuring system which really should be calibrated out.

[stratotarts]

It's true that the excitation signal does not have to be a sine sweep. But I was speaking in the limited context of the Rightmark software in particular. I don't think it has the ability to use tests like the multi tone for the purpose that you describe. Are you referring to the roll off, above or below 100Hz? Or both? The roll off below 100Hz is a normal artifact of the integrator response, and also the response below 100Hz is normally not interesting (i.e. it's virtually the same for all pickups). So my plots, at least, don't include any information below 100Hz unless I am testing the integrator.

However, the roll off between 100Hz and the resonant frequency, is suspicious and the remarks I made about test signal levels were directed at that. It could be a sign of too low, or too high, test signal levels, a result of either noise, or distortion components respectively. A typical humbucker plot does have some of this "rise" but it seems a little too much in this case. It would be interesting to see a plot of some known pickup that I could compare to, using the same test set up.

It's possible that the "rise" is visually exaggerated by the inclusion of 10Hz-100Hz, too. So a normal plot but expanded. Here is a wide range test plot to show what I mean. The middle (blue) plot is loaded. You can see only sub-1dB difference in the flat region.

[/url

Looking closer, even more pronounced flatness. The two peaks show the effect of clipping on the test signal - the peak amplitude is reduced:

In the plot posted in the first message, the amplitude begins to fall off above 100Hz. That is suspicious. It's possible that the audio device used as an interface, is not configured correctly or does not have an adequate low frequency response.

[aquin43]

I wasn't aware of the limitations of the Rightmark software and was speaking more generally.

I too tend to limit the response measurement to 100 Hz and upwards and it is the generally rising characteristic of the response above 100 Hz in this case that had me worried since I can think of no physical explanation for it so far from resonance within a conventional pickup. Only Alumitones have that extra low frequency roll off in the response.