Gretsch Filter’Tron, Analysis and Review

[antigua]

www.gretschguitars.com/blog/gretschtech/gretschtech-picking-the-pickups/




These were newly purchased on eBay. There doesn't appear to be any official product page for them. I don't know much about them, aside from the raw data that I've gathered below. 

I'm going to get fresh data for Fender Fideli'trons and TV Classics. That will be a fun compare and contrast. 


Gretsch Filter'tron Bridge - 006-2876-100
Series resistance: 4.97k ohms
Series inductance: 2.298H
Gauss: 250 / 300

Unloaded: dV: -1.4dB f: 9.81kHz (black)
Loaded (200k & 470pF): dV: -1.7dB f: 4.46kHz (red)


Gretsch Filter'tron Neck 006-2880-100
Series resistance: 4.18k ohms
Series inductance: 1.7403H
Gauss: 250 / 300

Unloaded: dV: -1.9dB f: 11.2kHz (green)
Loaded (200k & 470pF): dV: -1.9dB f: 5.42kHz (gray)


Bode Plot:


It can be seen that for the difference in inductance, 1.7H versus 2.3H, there is a bout a 1.2dB difference in the baseline output voltage. The driver coil voltage was right around 1.1Vpp.


Cover analysis:

As can be seen below, the Gretsch Filter'tron "H" cover is vastly superior to the PAF style cover. Both the Gretsch and the Seymour Duncan PAF cover are chrome plated brass. While nickel silver is a preferred material for pickup covers, the Filter'tron design makes the material a moot point. 

Unloaded:


Loaded:

[JohnH]

These Filtertrons sure are interesting little critters, so I thought I'd see if they model easily.

I get a good 6-part match for both N and B versions. But the values are unusual. The Inductance required in the damping branch of the model is of the same approximate value as the main inductance - very unusual, usually it is several x higher. Also the resistor in the damping branch is low, adding more scoop to the curves.

Models:


Curves:


Another thing, when I do the model derivation, I don't use the measured inductance directly, though I note it as a reference. Then, I  back-check by putting in a high capacitance on the model in order to create a resonance at 1kHz, where I believe the meters do their inductance measurements. Then I can calculate the net equivalent inductance from the resonant frequency and capacitance. This is a combination of the two inductors in the model, plus the other parts. When I did this here, my equivalent values were much higher than as measured: the Neck pickup came out 2.5H vs 1.7H measured and the Bridge was 3H vs 2.3H measured). Its a puzzle!

[antigua]

I measured the Strat and Tele pickups are 1kHz, but for the humbuckers I have switched to 120Hz at the advisement of Helmuth Lemme's guide www.planetz.com/wp-content/uploads/2014/10/Pickup_Measuring_Technique.pdf :

It measures inductance at either

120 Hz or at 1000 Hz. The 120 Hz figure

is reliable. However, the reading obtained at

1000 Hz is often distorted by the winding capacitance

and/or by the eddy currents in the

metal parts, so it is not as reliable as the lower

frequency

And he was using the same LCR meter that I have, and that most pickup people end up with, the meter that is sometimes branded as the Extech 380193

The logic is sound, I had been starting to question why 1kHz was preferred before I came across Lemme's guide.

The Filter'tron neck measures 1.355H at 1hHz, and 1.738H at 120Hz, so the inductance shows a higher value at 120Hz. An air coil pickup (coil is intact, everything else is removed) measures 1.502H at 1kHz, and 1.492H at 120Hz, hardly a change, so it's easy to see that the metal parts really do cause the inductance measure low.