Most modern guitar pickups are potted. That means they’re dipped in wax to prevent their components from vibrating against each other in high-volume situations, which can produce unwanted feedback.
The process also prevents pickups from becoming microphonic, amplifying sounds traveling through air along with the magnetic information generated by the pickups interacting with the strings. Some pickups are so microphonic, you can literally talk into the pickups and hear your voice through the amp.
Want to hear a pickup that sounds like a cheap megaphone?
Your wish is my command! I recently pickup up a cheapo semi-acoustic to use as a subject in fiendish pickup-transplant experiments in upcoming blog posts. The neck pickup on this bright red beauty is microphonic to the max:Seriously Microphonic
So unpotted pickups are bad, right?
Not exactly. Many beloved vintage pickups aren’t potted. These often have a resonant midrange thrust, a quality some describe as a “honk.” Those protruding midrange frequencies can really help an guitar sound find its place in a mix, or cut through the bass and drums onstage.
Seymour Duncan is savvy to this fact, and some of the company’s coolest pickups are unpotted. Examples include the the Antiquity and Seth Lover humbuckers. I recently used the latter to transform a dull, uninspiring Les Paul in the life of the party. (You can read about the makeover here and here.) The new Zephyr series pickups are also not potted.
I love the slightly nasal resonance of the Seth Lovers, but wish there were prettier terms to describe the quality than “nasal” and “honk,” which don’t exactly sound like compliments.
I recently asked Seymour about this while hanging out in his office. I wondered why there are so few unpotted pickups nowadays, considering how many players are attracted to their character.
He talks about feedback problems unpotted pickups can cause in high volume situations. Now, there’s good feedback (the violent but musical sound of, say, Jimi at Woodstock) and bad feedback (an obnoxious squeal that no one but an audio pervert could love).
Unclear on the difference? Let my use my Seth Lover-equipped Les Paul to demonstrate:
I cranked a small combo amp, added a germanium overdrive pedal, and placed the guitar right in front of of the amp. I got a nice wave of controlled feedback, with strong third and fifth harmonics. Yum.Good Feedback
Then I turned the amp all the way up, shoved the pickups right up to the speaker, and got a blast of bad feedback.Bad Feedback
Kids, don’t try this at home, unless you want to be looking for a new home. My apologies to my ever-indulgent next-door neighbors.
But basically, I believe feedback fears regarding unpotted pickups are greatly exaggerated. I encountered no bad feedback problems, even with a high-gain overdrive pedal and a maxed-out amp—I really had to go out of my to make the pig squeal. It’s hard to imagine anyone encountering serious trouble when using a vintage-style amp, even if they dime it. But yes, if you’re performing in front a large modern amp on the burn channel, you could get ugly shrieks, especially if you have a lot of guitar signal pouring from your onstage wedges as well as your amp. If that’s your style, you should definitely play potted!