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TouchMyApps host the original full-length review of the z02. For here, I'll get just to the sound portion as I feel that is most important to the majority of Headfi readers. As for how I got mine, I didn't. This is a loaner from Musica Acoustics. I've been shooting some of their product photos for the last while and get to listen to most of what I shoot. The z02 caused a stirring in my audiophile emotions before I even heard it, and afterward, makes me want one badly. Alas, mine was on loan and I've got to bring it back tomorrow.
Bugger.
Onto why I don't want to give it back:
Sound
Here is where the z02 differs from a traditional amp. It DOES have a good amp circuit included. And yes, that amp can drive even very difficult earphones such as the Earsonics SM2 with little to no effort. Yes, it is a powerful machine, even a good standalone amp.
But, if you’re interested in the z02, it’s possibly because you’ve had enough of amps and DAC’s that make your music sound the way the recording artists intended. You just want to have fun and enjoy your music. I understand completely. So do Digizoid.
They reckon that the bright red contour setting is good for movies. I reckon it is good for anything. In fact, the amp is at its best in terms of dynamic range and noise levels when its circuitry is clubbed out. That’s great news for me. I’ve been known to vacillate between earphones on a daily basis, but I always come back to the Audio Technica CK10, an earphone that could do with a bit of clubbing. My recent love affair with the DBA-02 MKII describes a similar outcome. Both earphones are considered by some as stark, boring, and metallic. Of course, fit is of grand importance with these earphones, but even with perfect fit, you won’t get heaps of bass out of either one.
Unless you have the z02.
Subwoofing power
Flick it to yellow, or if you dare, to red, and the z02 will give you club-level bass. Honestly. With a good seal, even bass-neutral earphones will rattle in your ears and you will swear your chest is pounding from 1-meter subs and that Paul van Dyk is on stage. That bass is clean, comparatively artefact free, and detailed. It is the best bass enhancement I’ve ever heard, even trumping Graham Slee’s Voyager headphone amp, a device that costs more than three times the z02.
In terms of raw data, the z02 can push around 15 decibels of difference between low and high frequencies, and focuses on the frequencies between 10Hz and 300Hz. It’s incredible.
Unlike traditional amps that have ‘EQ’ settings, the z02 allows you thirty-two levels of customisation. In other words, you don’t have to succumb to one company’s interpretation of enhanced bass. The power is completely in your hands.
There are no drawbacks to the z02 that aren’t present in other, more expensive audio devices. For instance, noise levels are on par with many amps that cost even give times the z02’s meagre sum. Yes, with sensitive earphones, you will hear white noise in the background, but it could hardly be called stentorian. To be honest, ALO’s wonderful The National headphone amplifier has as much background noise as the z02 does.
It’s a small price to pay for such lovely bass.
Distortion
Then, there is distortion. Quite a bit, to be exact. Driving the SM2, the z02 outputs up to 2dB of averaged noise and intermodulation distortion, mostly, you guessed it, in the bass. That is when the z02’s contour settings are orange or yellow settings, and again, under load. GoVibe’s VestAmp+, a fine-sounding piece of equipment has similar peak levels of IMD and noise under load, though its base levels of distortion in the low frequencies are lower by about 20dB lower than the z02’s are. In the high frequencies, however, that number reverses, and the z02 has the upper hand. Again, the z02 is much cheaper, smaller, and bounces when dropped.
Stereo image
Onto stereo separation. Phenomenal. This tiny piece of plastic, aimed at bass heads, sustains -73 dB (averaged) of stereo separation under load. It handles that separation well in the midrange, loaded or unloaded, but low and high frequency separation gets squashed as soon as the z02 is under load. It comes quite shy of my reference amp, ALO’s Rx, and in well under the GoVibe VestAmp+, but then again, the z02 costs less than a third of the cheapest of those? I will. And it does.
However, higher levels of distortion in the midrange and bass cause the z02 to sound a bit more muffled than a stock iPod. There is slightly less ‘sparkle’ in the stereo image, and of course, the z02 spends no energy in emphasising high frequencies which helps to paint a bright, separated sound picture. This is a subwoofer and emphasised bass tends to dull the perception of high frequencies. The quantitative effect is that even though the z02 sustains great stereo separation, it will sound sound more closed, more intimate than your most audio sources will for headphone use. As a subwoofer, I’d expect nothing less.
Dynamic range
I feel funny even bringing up dynamic range here, but I’ll do it. Why? Well, by nature, a subwoofer overpowers the perception of dynamic range, tipping everything to the floor and beyond. Still, the z02 is probably capable of exceeding the bounds of 16-bit audio, which is 96dB. I say probably because my equipment, while decent, isn’t professional, and introduces a bit of its own distortion into the signal. Still, feeding the Edirol FA-66, the z02 manages to push 94,6dB of dynamic range. Not bad.
But et’s be honest: if you are in the market for a subwoofer for your portable device or your living room, you are probably not worried about dynamic range. You want power, volume, and fun. The z02 delivers all of that, but just in case you need to validate your purchase, take a look at the graph below and remember, the z02 is under load. Incredible.
Charts Disclaimer This review’s RMAA measurements reflect the performance differences between the naked iPod touch 4G and the same iPod when paired with the z02 and Twisted Cables line out dock. Since these measurements are taken with my equipment, they should not directly be compared measurement-to-measurement to other technical data taken with different equipment. The data represent the ability of the amplification circuit to drive headphones and speakers.
Volume
Finally, let’s talk volume. With earphones, you will get more than enough volume for any use, ever. For large headphones such as the Beyerdynamic DT880 600Ω, you will get enough, but won’t be able to pierce your eardrums. Bugger. When hooked up to speaker systems, I suggest using the z02 as a preamp. It won’t give enough juice to smaller powered speakers unless in small rooms. Remember, this is a palm-sized device. It has its limits. But those limits are feeble in comparison to the myriad plusses the z02 has.
Niggles
I have only two niggles with the z02. The first is that in low gain mode, and with sensitive earphones such as the Sleek Audio CT7, even the lowest volume setting nears uncomfortably loud levels. The overall gain should be lowered even further, preferably to near zero levels so that users can comfortably adjust their music for any headphone or speaker. The second is that if you use the z02 near a phone or other radio-toting device, you will get beeps and boops from time to time. Those beeps and boops are radio interference. The z02 could be better shielded.
Sound Conclusion
The z02 is a good headphone amplifier that sustains relatively high quality signals even under difficult loads. In similar price categories there are few amps that can trump it across the board. The iBasso T3D is the only one I can think of off the top of my head that actually does. But that isn’t the only way the z02 defines itself. It is also a portable subwoofer that can be attached directly to headphones, powered speakers, car stereo’s, and powered microphones (yes, but I don’t suggest it). Don’t expect anything like it to hit market at any price until Digizoid’s push out the next z0.
Conclusion: Best portable audio device in years. Thank god for Digizoid. Thank god for the z02.
Again, TouchMyApps host the original full-length review of the z02. If you want the measurements, the pictures, or talk about build quality and features, go there.
As they always say, MORE BASS!!
