FMJ. Full Metal Jacket. A naming appendage lent by AudioQuest to a new version of its Jitterbug USB decrapifier that – you guessed it – comes wrapped in metal instead of the original’s plastic.

Whether used in series (in-line) or in parallel, JitterBug significantly reduces contamination from RF generated by a computer, car, or other device. JitterBug FMJ also thoroughly addresses environmental RF Noise taking advantage of this vulnerable interface.”

A hinged “rubber” door covers the JitterBug FMJ’s output. this “little black “door” is RF-proof thanks to the material being substantially RF-absorbing Carbon.”

“Either in series between any computer, smartphone, NAS, streamer, or car audio system and a USB input. For an additional sonic improvement, use a second JitterBug in another unoccupied USB port—in parallel to the first—except with JitterBug FMJ’s front door closed.”

a 2nd JitterBug in parallel is always a delightful improvement as it pulls more RF Noise off the USB power bus—which is why and how a JitterBug makes just as big an improvement even when plugged into service-only or update-only USB ports on many devices.”

The Jitterbug FMJ will likely bring audible improvements to the sound of its DragonFly Black and Red USB DACs, the DragonFly Cobalt already houses Jitterbug technology and adding an external Jitterbug in series will cause mileage to vary.