In the first of this four-part series of articles we set the scene. Clean power matters in audio, and is something you might want to consider. Put simply, if your mains supply is dirty can your system perform to the best of its abilities? I’ve long been an advocate of external power supplies for example, finding they elevate the performance of equipment quite notably. Got a Raspberry Pi-based streamer? Treat yourself to a £60 iFi iPower 2 power supply and see what difference it makes.

But what about mains cables, conditioners and the like, are they worthwhile too? That’s something we’ll explore in the next two articles. Here we’re focusing on a device colloquially known as a ‘decrapifier’ (love that word!) Something you plug into your system that filters out electrical pollutants. Rather than act on the mains, Audioquest’s Jitterbug FMJ works on the delicate 5V USB signal from your noisy phone or computer though. Clean up the signal and you’ll reap the benefits downstream.

Well that’s the theory, and with a UK street price of around £40 the Jitterbug is very affordable. Does it make a difference? And if so, is it worth the hassle of adding yet another (little) box of tricks into your system? Let’s see……….

Jitterbug FMJ

The latest ‘Full Metal Jacket’ version of the Jitterbug was launched 3 years ago. It looks like a dongle-DAC and sits between a USB socket and the downstream DAC. The body is made of metal, with a rubber & carbon-fibre door at one end. Open the door to plug a DAC in. Keep it closed to use a second Jitterbug in an adjacent USB socket (which supposedly ‘sinks’ more electromagnetic radiation). 

I tried the Jitterbug FMJ in three scenarios; with my phone into headphones, with my laptop through headphones, and with the same laptop playing into a full system.  


First up was my Pixel 7 phone with an Audioquest Dragonfly Red (£169) plugged directly into the Jitterbug, which connected to the phone with a standard OTG (On The Go) cable. 

Playing into Grado SR80X headphones, Taylor Swift’s ‘Fortnight’ (from The Tortured Poet’s Department) sounded really good; as always the Grados retrieved oodles of detail. The upbeat nature of the track also suited the Grado’s forthright presentation, which favours rhythm and drive over refinement. 

The difference the Jitterbug made frankly surprised me though. The synths were bouncier than before, there was more meat to the sound and more detail on display. Towards the end of the track when things get really busy the Jitterbug also controlled the cacophony better.

Switching down a gear to Gregoire Maret’s new album, Ennio, the benefits were again obvious. The beautiful playing, coupled to sensitive arrangements, made for an enthralling listen. With the Jitterbug in situ the sound was more measured, the silence between notes quieter (if not totally quiet). The instruments were also better delineated, you could hear the contribution of each better. Overall the sound was cleaner.

On both tracks the differences weren’t night and day. They were enough to sell me personally on the Jitterbug though given that a ‘phone plus dongle-DAC’ is my go-to solution for portable audio. Note that I tend to listen when stationary, for which it’s worth the faff of hanging a Jitterbug off my phone. If you listen on the move you may find otherwise.

Computer / headphone amplifier

Next up was my laptop running Audirvana software, playing into iFi ZEN DAC V2 (£200) and Schiit Jotunheim V1 (£400) headphone amps. Both have internal DACs that I fed from the USB socket of the laptop. Headphones were Audioquest Nighthawk Carbons (£699). 

The ZEN DAC went first with the Gregoire Maret track, and I concede the improvements wrought by the Jitterbug were smaller. But, they were there. The piano had a little more body to it, its sound more stable. The background electronic drone was also more audible, better defined with the Jitterbug in use. Overall the sound had a little more presence too.

It was the same with Taylor Swift’s ‘Fortnight’, where the low-level detail of a more complex mix was easier to hear. Background vocals, supporting synths and a host of other subtle effects came across better. And the prominent synth line that underpins the track was, again, bouncier. Not huge differences but well worth £40 for a slightly cleaner sound. 

Switching to the Jotunheim gave a distinct upturn in sound quality overall compared to the ZEN DAC V2. Which I expected; I know the Schiit and Nighthawk Carbons work well together. Much listening ensued, switching between the Taylor Swift and Gregoire Maret tracks, swapping the Jitterbug in and out of circuit. Ultimately I concluded it made no discernible difference. It seems Schiit has done a good job in excluding noise from the Jotunheim. 

Full system

A trend seemed to be emerging; the better the partnering equipment the less difference the Jitterbug was making. Would that negate its use in a good Hifi system, where the electronics are designed to reject noise anyway? Or might a more revealing speaker allow the Jitterbug’s impact to be heard? 

Firing up Audirvana on the laptop, I fed it into a Mytek Liberty 2 DAC (£1,295) and from there to a Musical Fidelity A1 amplifier (£1,500). That drove Mobile Fidelity Sourcepoint 8 speakers (£3,000 – Darko review here). Same tracks, with and without the Jitterbug between laptop and DAC. 

With the quieter Ennio album from Maret I was pushed to tell any difference.

Initially it was the same with Taylor Swift, but switching back and forth, differences emerged. With the Jitterbug in circuit the sound was more confident. Transients were sharper, giving the lead synth yet more bounce factor. Subtle variations in tone and texture were also more apparent, as were the different elements of the complex mix. The track sounded more upfront. 

Which, I confess, surprised me. So I went back to listen some more. This time to Maya de Vitry’s ‘Stacy, In Her Wedding Gown’ from the album Infinite, a lovely singer-songwriter track with subtle accompaniment. Again, the Jitterbug managed to wring improvements. A slightly firmer (acoustic) bass. Leading edges were better defined, the acoustic guitar had a tad more bite for example. And de Vitry herself came across as slightly more poised. The improvements were certainly marginal but the Jitterbug proved effective, its £40 cost irrelevant in the context of a £6,000 system.


The Jitterbug is probably not a universal solution, its efficacy dependent on where you use it. Plug it into a dedicated streamer, one where the designer has minimised noise anyway, and it’s unlikely to have much effect. 

It fitted several of my scenarios though; consider it part of my portable setup now for example. And even where its improvements were marginal the cost/benefit equation was off the scale. I mean, £40? That’s prime impulse-purchase territory, where you buy one and then work out where to use it. A Best Buy Award is therefore a no-brainer. 

Which makes for a good start. In the next article we’ll look at the Isotek EVO3 IsoPlug that does the same as the Jitterbug, but for mains. Plus three mains cables at differing prices. Will we hear similar benefits to those brought by the Jitterbug?