Fret buzz suddendly appeared on my Strat with high strings, good relief and nut?

[Pierre]

Well I've had my Strat with the same setup for a long time. Strings about 5mm off the fretboard, a consequent relief I never bothered to measure and I just loved this feel. I can also play slide on it.

I've recently re-strung it and straightened the neck a little. I didn't change the strings brand/gauge at all.

I lowered the strings to about 3mm and set the neck relatively straight. Then I gave it a quarter turn at a time and kept getting buzz on the open and fretted strings. The former + latter syndrome usually indicate a too low nut but this was never the case with this guitar and the nut is fine.

Relief is measured with a capo at the first fret, fretting the 17th fret and between the 9th fret and the low E string.
String height is measured free of anything (no capo).

I've now reached 0.012 inches of relief and a 3mm string height (2.3mm with the capo at the first fret), and I still get the same buzz.

This is the first time I've encountered this kind of buzz when setting up guitars (my own or others). This guitar had never buzzed before and this started appearing just with the new strings/setup three days ago.

Any ideas..?

[WezV]

you sure its fret buzz and not some other sympathetic vibration like loosened tuner bushings or other parts?

hard to diagnose anything else over tinternet

[Pierre]

Yeah it's really the strings on frets. First thing I do before AND after a thorough cleaning (part of any setup) is tighten every single thing that can potentially be tightened.

[FELINEGUITARS]

What pickups are on there?

We've seen this problem before and itcan be caused by over strong magnets pulling the strings  so that they rattle against the frets.

The Fender noiseless are bad for this - Samarium Cobalt magnets!

Try backing off the pickups

[Pierre]

I have two Duncan single coils and a BK Crawler. In fact this was one of the first things I tried... I tried to cancel out every factor I could (nut, frets are in good shape, with relief or flat neck, pickups at normal height or all the way down).
In fact this was part of the reason why I wanted to lower the string height; at 5mm off the fretboard, I need the pickups higher than normal. But when I fret notes, they get very close to the polepieces (too close). It also makes it even harder to balance out the single coils and the humbucker. With the strings at a more normal height this issue would have been solved.

Thanks guys... I know I did something weird somewhere down the line. I've reset the neck straight as can be and I'll re-work the setup from scratch. Strings are new.
I think mostly I'm disappointed that this happened. This guitar is my baby and I'd never had any buzz whatsoever before, I knew her setup by heart and her and I had a healthy relationship... ;) Whatever's left of my pride is a wee bit hurt!

Another factor is that the appartment is very warm due to it being cold outside. Warm and dry though. That's why I had to adjust the neck in the first place.