Sound
So as not to change styles too much, let’s first talk about hiss. There’s almost nothing to talk about. Whistle hisses about as much as a high-end DAP, which is basically not at all. This is a saving grace when pairing with sensitive high-end earphones (with which Whistle sounds great) such as Campfire’s crazily sensitive Andromeda, Noble’s K10, Ocharaku FLAT4, and more. It also keeps IMD and jitter to inaudible levels through every earphones and headphone I’ve tested. Its drive sweet spot is high-impedance earphones and headphones, but because it won’t get that much voltage into your big Beyers, it’s best paired with headphones of less than 300Ω whose sensitivity ratings are around 100dB. Portable earphones and headphones of any stripe will get loud and at every volume level be driven full and free of IMD and jitter.
As you’ll notice in the attached graph, irrespective the load, Whistle’s frequency response neither tips nor peaks. Where it takes steep and predictable hits are in stereo cross-talk and IMD. Driving the Earsonics SM2, IMD jumps 142x from 0,0043% to 0,486%; even at such extreme volumes, and despite the jump, IMD peaks are inaudible. Whistle’s weakest genre is portable headphones like Audio Technica’s ES7, which, at maximum volume creams its noise levels, THD, and stereo cross-talk. At test volumes, both the first and the last could be audible at the machine level, but at typical listening volumes, the effect will be much less pronounced.
Whilst playing back DSD files, Whistle heats up and drains more battery, but retains the same equitable stereo depth and excellent transients from top to bottom. It’s hard to fault Audirect. Whistle is just warmer than neutral, produces a signal several decibels louder than the loudest iPhone (and which approaches levels seen only in high-end DAPs), and it keeps hiss noise as low as possible. Its flat-field stereo image is amazing, giving good z-axis room in any frequency, though because highs don’t particularly stick up, doesn’t sound as wide as some DACs, REI for example.
Apart from dropping volume several decibels from maximum when driving certain multi-armature earphones, it’s surprising is how well Whistle drives high-end earphones, remaining stable, keeping a strong signal, and maintaining its straightforward signature. In some ways it is obscene. In my amateur tests, the only similar dongle to beat it across the board is REI. REI is also the most powerful and expensive of every such dongle I’ve tested. TAKT makes a great show except for in stereo separation, and Spectra’s dynamic range takes a dive.
Whistle is solid.
Full measurements and comparisons here: RMAA Audirect Whistle 24-bit
End words
It’s frustrating that so well performing a device is so quietly and awkwardly marketed. Whistle performs where it counts, sounds good, looks okay, and at its price point dominates the competition landscape that these ears have heard. It lacks external controls, but has great plug-and-play branding. There’s glue here and there, and its machine works is just okay. It’s a great buy, but you’ll be damned if you can find one to try out. Anywhere.
With Whistle, the age of mature Lightning and Android audio dongles is here. 99$ today outperforms 1000$ DAC/amp stacks that dominated the market just a few years ago, and it does so in a tiny package. While I’ve yet to try a Dragonfly, I’ve tried REI, TAKT, Spectra, Whistle and a few others. REI, of course, is flawless, nearly replacing for a high-end DAP. And Whistle, which goes for 99$, nips at its heals.
Well done.
