Tone pots and frequency boost: 1 Meg giving me too much 3k ice pick

[burgrluv]

My jag has always had this unpleasant resonance at 3k (particularly on the bridge pup) that prevented me from ever putting the treble past 6. As a result, the tone would get harsh before it ever got glassy.

Last night I put a parallel resistor on the tone pot for shits and giggles and brought the value down to 250k. To my surprise, I was now able to push the treble much harder without ever hitting that same pesky 3k hump, allowing all the extended highs the chime in undisturbed.

Is the 1 meg pot pushing 3k by design? And is there a way to fine tune my setup to push a more musical frequency, basically anywhere between 4k-7k.

I even used a spectrum analyzer to make sure it wasn't in my head, and sure enough there was a very noticeable peak right around 3k when running the tone pot at 1 Meg.

I suppose that I'd be fine with keeping the tone pot a 250k, but I'd rather avoid having the treble dimed at all time if I can.

Thank you for any insights in advance,
Cheers

[Embenny]

Higher value pots increase the Q of the resonant frequency, which is quite spiky for Fender style single coils.

Lower value pots smooth out the resonant frequency, and added capacitance shifts it downward. Bill Lawrence wrote a lot about this. Apparently the high capacitance of 60's coils cables was enough to drop a Strat pickup's resonant frequency down into PAF range, which is what Jimi Hendrix did in the studio.

[timtam]

The Pure Vintage 65s are the only Fender* jag pickup that have been analysed in any detail.
https://guitarnuts2.proboards.com/threa ... sis-review
There is currently no similar analysis of Fender's AVRI 62-style pickups.

*FWIW the Squier DD pickup in the VM jag have also been similarly analysed.
viewtopic.php?f=7&t=107830

That PV65 analysis shows they have an unloaded resonant frequency around 7.5 kHz. In order to facilitate comparisons between pickups, testers usually standardize on a 'loaded' test with 200k resistance and 470 pF capacitance. The former is designed to be somewhere between the resistance load of two parallel Les Paul pots and strat/tele pots. The latter simulates guitar cable capacitance. They're important because both change a pickup's resonant frequency in height and frequency. That loaded test on the PV65s yields a dampened resonant peak of around 3.4 kHz.

https://guitarnuts2.proboards.com/threa ... sis-review

Unfortunately that's not much help in the specific case of jag pickups, which of course usually have two 1meg pots in parallel, and capacitance varies rig by rig.

Edit: following written at the same time as mbene085's post above, and covers similar ground !
Lemme shows that different resistance loads tend to attenuate the resonant peak (lowers Q factor), rather than shifting it (hence the 'brightening' effect of 1meg pots is related to the prominence of the pickup's resonant frequency, in relation to mids and lows). Capacitance loads OTOH tends to shift the resonant frequency.


http://www.buildyourguitar.com/resources/lemme/

[burgrluv]

Great, thank you for the info. Seems like I've more or less found the optimal settings for these pickups then. I put the bright cap back into my DR and it's a great match so far, treble is sitting around on 6-7 with plenty of highs to go around.

[Larry Mal]

*FWIW the Squier DD pickup in the VM jag have also been similarly analysed.
viewtopic.php?f=7&t=107830

I don't have much to add other than this is an incredibly well written overview of the Jaguar pickups and I wish there was a whole lot more of that sort of thing.

[Embenny]

Yeah, Antigua does amazing work that pickup winders and guitar magazines should be doing but aren't.

He's looked at a lot of Gretsch pickups too, and his analysis was super informative.