Jitterbugs have been permanent fixtures in my chain for almost six years. One sits between the Auralic Aries Femto and the Mytek Manhattan II, the other on a USB input of the Apple TimeMachine. In the meantime, Audioquest has reissued its successful model and equipped it with a metal housing: The Jitterbug Full Metal Jacket, or FMJ for short.

Since in the meantime, the TimeMachine no longer acts as a router but only serves as a backup, and it is isolated from the system via fiber optics and ADOT media converters just like the current router, I should perhaps check whether the Jitterbug still has any effect at this point. However, I wouldn't want to do without the one between the Aries and Manhattan by any means, even though the Aries must output a pretty clean signal, as experimenting with a Mutec Reclocker at this point has shown: At this point, the Mutec did not deliver any clear improvements. One could benevolently say that it made for an even calmer sound, but Roland Dietl and I agreed at the time that, used after the Aries, it made the reproduction seem tedious and unexciting. A Jitterbug, on the other hand, did what it almost always does at this point: it made the imaginary stage appear even more extensive, improved audibility, and presented dynamic contrasts even more impressively. And if I ever need music data directly from the MacBook's USB port for tests, a third Jitterbug is always part of the package.

But now to the new FMJ: Besides the material of the case, the closure of the rear USB socket has also been changed. It is now connected to the case, and carbon fibers are incorporated into the rubber to absorb high-frequency radiation. In the product information, Audioquest also mentions a "discrete dual circuit for noise dissipation" but does not state whether this was also found in the old Jitterbug and how it works exactly. The only way to get more insight into the Jitterbug FMJ is to try it out. While its developers recommend using it in conjunction with the DragonFly Black and Red, they do not make a clear recommendation for use with the Cobalt, which also contains parts of the filters used in the Jitterbug.

For a first encounter, I try out the Cobalt with the old and new Jitterbug. That is with Shostakovich's Symphony No.15 from an external USB hard drive. Audirvana acts as a audio player. Even in combination with the DragonFly Cobalt, the Jitterbug brings clear sonic advantages: You get a more realistic idea of the recording room. Even though I can't experience a depth gradation via headphones - in this case, the Sendy Audio Aiva - the individual instrument groups are now more clearly separated from each other, also spatially. The timbres are warmer, and the high frequencies do not even have a hint of roughness anymore. The reproduction also shows a bit more dynamics now. But you and I already knew that the Jitterbug almost always has a beneficial effect. So, I listen to the first movement of the symphony again with the Jitterbug FMJ. To say it right away, the differences here are not massive. When switching to the new model, the first thing you notice is that the music now flows a bit smoother. The piece also seems a bit more rhythmically exciting – an impression reinforced when the original model is inserted again between the MacBook and the DragonFly. As so often, the change for the better seems less spectacular, but the way back makes the previously achieved improvement ear-catching.