I too am shocked to find no info on Fred, and having recently acquired one I suppose I'm now qualified to comment.
I was highly skeptical about Fred for all the wrong reasons...despite owning a large chunk of Mr. Satriani's catalog, the one thing I have never liked about his playing is his tone, especially on his classic records. I had always assumed that the uber-fizz tone that's all over SWTA and FIABD was a function of Fred.
I have never been more happy to be wrong about a pickup.
Below is some information about what guitar it's in, to give context. for those not interested in that, skip down below the line of asterisks.
I've got it in the bridge of a Raven model from up and coming guitar builder Jack Dent (jackdentguitars.com). Carved top double cutaway with Mahogany body, mahogany neck, thick maple top, and rosewood fingerboard. The neck joint is like a cross between set neck and neck-thru- one piece mahogany back has a channel from end to end in which the neck is set, through the whole length of the guitar.
I mention all this to give context for the pickup description. This guitar overall is surprisingly bright and very, very clear in tone, while still retaining a very strong but tight bass presence.
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I was concerned Fred would be too bright, as I've always heard it described as a very bright pickup. And to be sure, it IS bright. Awesomely clear and defined, but still with plenty of bass presence when gained out.
Surprisingly to me it REALLY shines when played clean. I play a telecaster often when I'm not playing my Raven, and the Fred comes closest of any humbucker I've ever played to delivering the immediacy, brightness and cut you get from a tele bridge.
Now before anyone reads this and thinks "I don't like bright pickups," read a little further. I historically haven't either. My favorite all around bridge pickup is the Tone Zone (I should say "was" now that I've tried Fred). I cannot overemphasize this fascinating quality it has of seeming to have this big, lovely bass presence come out of nowhere as you add gain. But it's still perfectly clear and tight. The DM website says that in contrast to other humbuckers that get fatter with added gain, Fred gets "tighter and brighter." I can't agree with that- it does NOT get brighter, but it doesn't get at all muddier either. I wouldn't argue with the idea of it getting "tighter" since to me that's a harder idea to put my finger on.
What I will say is that no matter how the gain is piled on there is still a very clearly present "space" between the notes. It has all the good qualities of the Humbucker from Hell used in the bridge (clarity, clear bite in the high harmonics) but without the overly biting tone that can get ice-picky, and without the total lack of low end. Sorry for the double negative there...you get my point.
Could say more (and probably will). Hope this helps someone.