On keeping up with Mojo
PUREII and DUOII are the most channel balanced amps I’ve used which don’t make use of digital volume control or an R2R resistor ladder. At minimum volume settings, each favours the right channel by around 5dB. Critical balance is achieved well below comfortable listening volumes for a majority of earphones and headphones. Volume gain settings are interestingly laid out. They go like this: low, high, medium. The benefit of this system is that it is difficult to accidentally trip to high gain on the way to medium, and burst your ears.
Mojo reaches insane volumes. And even when feeding DUOII 118dB of signal, I am able to get a comfortably channel balanced signal through Ultimate Ears’s Reference Remastered early on, with only a minute turn of the pentameter. PUREII/+ balances a little earlier on, which makes me recommend it over DUOII for earphones like Shure’s SE846 and Ultrasone’s IQ.
Some Mojo owners complain that its highs can can harsh or brittle. I get the criticism, but only academically. Mojo’s highs are slightly tripped up, but only just. It’s like 0,2dB, or so, and likely inaudible to all non-bats on the planet. However, high mids remain as free of crosstalk as mids and lows. Only in the extremes do they begin to fall, and even then, it depends on the load. Earphone users may find Mojo to be A-Okay, while headphone users may find it sounds a bit harsh.
Like all Vorzüge amps, DUOII kicks an even-Stephen signal from 20Hz to 20kHz, which means that that slight uptick Mojo feeds goes on through, unedited.
That said, there is a small closing of high-frequency stereo separation. At 118dB, Mojo kicks out around -118dB of crosstalk. DUOII bottoms out at around -60dB from an average of -80dB. After testing dozens of amps and DACs, I have found that closing of crosstalk can yield more natural sound stages that, at least at the ear, sound more 3D, with deeper Z-axis sense of space. Spatial positioning of instruments is also more natural. For these reasons, it is my opinion that through Vorzamp DUOII, Mojo’s highs are tamer, smoother, and they interact more naturally with the midrange and bass, which lie pretty evenly at around -80dB. Your mileage may vary, but my ears tell me that DUOII’s highs are less wild than are Mojo’s.
On all other fronts, Vorzamp DUOII keeps up. Mojo’s incredible speed of attack and decay and low noise floor remain as is. Actually, DUOII kicks out slightly less line noise than Mojo, which is extremely beneficial to sensitive earphones.
On transforming old favourites
The other DAP I love, and probably always will, is Astell&Kern’s original AK100. I love its footprint. I love its battery life. I love its DAC. I love that it swallows dual micro-SD cards (currently I’ve got dual 200GB cards in it). Unfortunately, like the iPod 5G, it hisses too much. And, it has trouble stably driving low-Ω loads. Unlike the iPod 5G, it doesn’t do gapless playback.
But when all its ducks are put in a row, it sounds great. But even with mods like Ryuzoh’s and Red Wine Audio’s, it kicks annoying amounts of hiss into sensitive earphones. The only mod that fixes that is Mezzo Hifi’s. Each one is invasive, though. Adding DUOII or PUREII, isn’t. That Vorzüge’s amps almost perfectly match the AK100’s footprint is icing on the cake.
Measurably, DUOII more than keeps up with the AK100 no matter the modification.
The iPod 5G’s warmer, smoother sound is perfectly stabilised when feeding the Vorzamp DUOII. And to be honest, if there were a high quality modification for the iPod 5G, that both stabilised the signal and removed its hiss and other signal anomalies, I’d be hard pressed to use any portable amp. But there isn’t. And, DUOII is more versatile still.
I use it to adjust volume of my BeoLab 8000 powered speakers as well as an ad-hoc subwoofer.
DUOII’s signature feature is its dual-stage EQ. As I hinted about above, it stands in place a subwoofer behind my BeoLab 8000 speakers. The same is true for the iPod, whose EQ distorts horrendously.
The first stage raises low frequencies from around 10Hz to 30Hz by around 3dB, and progressively less until 100Hz until the signal reaches zero gain. The second stage raises the same frequencies by up to 12dB. Depending on the source material you have to make sure to lower the input signal. With Mojo set to 118dB, Markus Schulz’s Mainstage, which reaches down to 20Hz, causes every headphone I own to distort with any of DUOII’s EQ settings engaged. Lowering Mojo’s volume to 100dB and raising Vorzamp DUOII’s in compensation, fixes that.
My PS1000 is far less sensitive to extreme adjustments to frequency response and distorts less than any of my earphones even at 118dB. Devices that output less voltage also keep Mainstage and other low-voiced bass distortion down when applying the EQ.
Most of my music reaches nowhere near as low as does Mainstage. As a result setting DUOII’s EQ to the second position returns nothing but clean, massive bass and around a 2dB uptick in highs. It’s not so much a v-shaped curve as it is a mellowed, and lop-sided U-curve. Because it doesn’t engage mid or high bass frequencies, it never reverbs, or splashes. Nor does it boom.
It is a careful, assiduously controlled EQ.
Choosing between PUREII and DUOII isn’t as easy as deciding on EQ or not. Although minute, PUREII outputs highs slightly muted against DUOII, EQ on or off. The differences are minimal, but they exist.
PURE II may also be a smidge more stable at extreme volumes – volumes beyond which I comfortably listen through any headphone. Both amps are extremely powerful: able to turn many high end headphones into speakers. As is common with battery powered amps, sensitive, low-Ω headphones are powered less stably at extreme volumes than through a good mains amp. That said, Vorzamp DUOII is more than a match for most high-end integrated DAC/amp solutions, all the way up to and including the Lynx HILO. DUO scales incredibly well.
Loaded, and at volumes approaching high-end DAP maximums, it keeps both THD and IMD distortion under 0,015%, which is far stabler than any modern hi-end DAP. And, DUOII powers hungry headphones very well. More powerful still is MyST’s PortAMP II. Of course, as more of a battery-powered desktop replacement, it is more than treble the size, and it lacks the EQ system.
The VorzAMP DUOII occupies a unique niche in which it has no real competition. There are few battery-powered amps more powerful than it. There are a few that measure better in any area. But no amp I’ve reviewed, and no amp I’ve tested, packages the DUO II’s performance with such a badass EQ system. And no amp company I’ve dealt with is so demonstrably dedicated to a platform.
Now, what to purchase as a high-end amp in a post-amp audio world? Or, is this a post-amp world?
I miss the simplicity of a solid source device with great controls, gapless playback, and a classic DAC. More and more – and despite the fact that I’m not a portable amp guy – I find myself attaching Vorzamp DUOII to my iPod 5G and truly enjoying my music. I understand that the iPod is a huge limiting factor. And yet, the combination rocks. At my desk, I can power DUOII from my iMac, and feed it from my HILO, knowing both academically, and in my heart, that DUOII exceeds the next best device in my audio chain.