ZO3 Headphone Amp Contours

First Look: ZO FS (aka ZO3) Headphone Amp

We’re so excited to announce the upcoming release of our third product, the ZOFS (aka, ZO3) headphone amp (“FS” is for SmartVektor “FullSpec” technology). An obvious succession to our first two products, ZO and ZO2, the ZO3 has been a long time coming. While we aren’t ready to divulge all the specs yet, we can give you an in-depth look into the design of the product.

But first, here’s a quick overview:

  • SmartVektor ‘FullSpec’ technology (low & high end adjustment)
  • SmartVektor on/off
  • Standalone headphone amp turns on when SVT is turned off
  • High voltage output for use with high impedance headphones
  • High current output for use with sensitive IEMs
  • Granular digital volume control with 256 steps (0.5dB increments) plus mute
  • Very low output impedance (< 1.5 ohms)
  • Extremely low noise & distortion-free
  • Easy to use & adjust w/numerical indicators
  • USB-rechargeable
  • Small, portable form factor
  • Custom aluminum enclosure
  • 100% Made in the USA

So let’s take a further look at all the ZO3 goodness…

SmartVektor FullSpec Technology

ZO3 Headphone Amp Frequency Response
Click to Enlarge. Frequency response plot of the ZO3 headphone amp. Note: only 9 of the 32 contours are shown.

The most exciting feature we’ve added to the ZO3 is our FullSpec SmartVektor technology (SVT). What is that you ask? Well, if you’re familiar with the first two versions of the ZO, you’ll know there were 32 levels of bass (i.e., contours) to select from (referred to as SmartVektor ‘LoFreq’ technology). But now, the ‘FullSpec’ technology adds 32 levels of treble adjustment to the mix – giving you a total of 1,024 different bass & treble combinations to choose from! Some other things to mention are that the steps are linear (meaning each increment/decrement provides the same amount of bass/treble change). Also, the max contour on the low end is at the same max dB as ZO2, but has less roll-off (i.e., the bass is deeper).

Standalone Headphone Amplifier

Similar to some of the previous ZOs, the ZO3 gives you the ability to turn SVT on & off – but with one significant difference. When SVT is turned off, all circuitry associated with SVT is bypassed and a secondary amplifier is enabled:

SmartVektor On vs Off
Click to enlarge. When SVT is turned off, all circuitry associated with SVT is bypassed and a secondary amplifier is enabled.
The same type of op-amp, configured to have the same headroom and power, is used in both the SVT circuit and standalone amp. The only difference is the standalone amp is tuned to have a completely flat frequency response. Switching SVT on & off is totally quiet (no pops or clicks), and the volume/gain levels stay the same.

General Audio Performance

  • Single gain level (even with a line-out level input)
  • Extremely low noise (every component was selected to keep noise levels at a minimum)
  • Low output impedance
  • Will drive up to 300 ohm headphones with authority
  • High voltage and current output for driving both demanding headphones and sensitive IEMs.
  • Large headroom
  • High power with ultra low noise & distortion
  • Accepts a 2Vrms input (line-level signals)
  • Charges via micro USB
  • Uses film capacitors & resistors
  • No output capacitors (less noise & distortion, lowers output impedance)

High Performance Components

Digital Volume Control

  • Digitally-controlled analog volume control
  • Designed for professional and high-end audio systems
  • 120dB dynamic range (-90dB to +30dB) with 0.5dB steps
  • 256 total steps
  • Mute (at -90dB)
  • Noise-free level transitions (zero crossing detection)
  • Low noise & distortion (THD+N = 0.0002% @ 1kHz)
  • Low interchannel crosstalk = -130dBFS

Film Capacitors

  • Low distortion (one of the lowest of all capacitor types)
  • Ideal for noise suppression & audio coupling circuits
  • Less noise generation at higher power levels
  • No induced microphonics
  • Study showed better subjective sound quality compared to other capacitor types:

Plastic Film Capacitor Sound Quality Chart

Click to enlarge. Subjective sound quality testing results of audio circuitry using plastic film capacitors. Pulled from the original ECPU datasheet.

Film Resistors

  • Tight tolerances (0.05%)
  • Highly precise & controlled (tight TCR)
  • HIgh performance (low current noise, minimal non-linearity)

So there you have it, your first in-depth look at the ZO3 headphone amplifier. Please tell us in the comments… what are you most excited about?

45 thoughts on “First Look: ZO FS (aka ZO3) Headphone Amp”

  1. How will the ZO3 compare to Creative Labs new amplifiers the Sound Blaster E1 and E3?

    What is the estimated battery life for the ZO3?

  2. How will the ZO3 compare to Creative’s newly announced amplifiers the Sound Blaster E1 and E3?

    Any idea on battery life for the ZO3?

    Thank you.

  3. How can I make sure I am able to pre order. I have have he-400, xb-500, JVC xx 77, and westone 3. I need bass.

  4. they say that zo3 is very mobil amp, mobile phones or cd players, but how it works with my denon rcd-m38 and my xb-700 headphones. i am really basshead person and i like digizoid.

  5. Hi,
    Are you able to give the dimensions out yet?
    Because ZO2.3 recently got stolen and I wanted to know whether or not to get another on or just wait for the ZO3. I’d also like to know the size because the ZO2.3 matched up perfectly with my Ipod Nano 7th gen (which also got stolen). So I’d really like to know the dimensions to decide if I should go with that pair again which I REALLLYY enjoyed with my HIFIMAN RE-400. Or whether I should wait. PLEASE

  6. This all sounds awesome and I look forward to the release but honestly I’m more concerned with how this handles line out.

    On the zo2.3 i either had to use another amp in the chain to boost the volume or go without and not be able to adjust volume on the zo2 unit.

    Will we finally be able to control volume levels in line out Lo gain mode?

    1. So the ZO3 will not have a low/high gain mode. It will easily take a line level signal, and you’ll be able to adjust the volume from mute to VERY loud (from -90dB ro +30dB, or 120dB total dynamic range). Since the volume can be adjusted in 0.5dB increments, you will also have a MUCH finer volume control adjustment.

  7. Hi,
    I’ve now just broken my 2nd fiio e6 whilst waiting for the z03. Please give me some positive news on a release date :-)

  8. I need a headphone amp in the near future within a month and for around the 125 price point. Would it be wise to buy the zo2 or will it be wiser to wait for the zo3

  9. I really want a ZO3, but given it’s not out yet I wanted to buy a ZO2, but I can’t find those available anywhere… Does that mean the ZO3 is coming out any day now?

  10. Will You Ship Pre-Orders Internationally ? I Live In Doha – Qatar So..
    Really excited about your product, I was about to buy the ZO2 But My Friend Informed Me That The ZO3 Was Coming Out Soon So I Cancelled My Order :P
    Another query , as you’re aware the XB500’s are the bassiest headphones, so will the ZO amps provide me with a noticeable change to the already super bassy headphones ? |
    Please Give a feed back

  11. I’m always very excited about improvements and I congratulate you folks on making the decision to improve and refine your excellent product.

    Some questions:

    1.) Will you be providing an up to date listing of all your authorized dealers that will sell this product. How soon after you announce the product will your authorized dealers have this product to sell to the public?

    2.) Will you offer spare cables and other parts that one may need to replace if broken or lost or if one wants longer cables than the stock ones that come with the product?

    3.) Will you be providing enough specs or stats so that we can effectively match headphones to the product?


    1. Thank you Rex! We will be providing an up-to-date listing of authorized dealers; however, for U.S. sales, we are focusing sales via Amazon. We have always offered spare cables at basically cost to those who have contacted us. I believe our cables are currently out of stock at the moment, and I’m unsure as to our plan for offering spares in the future. And to your last question, we have always done our best to provide enough information to help people make these decisions, ex: http://www.digizoid.com/?p=zo2#specs
      If there is additional information you would like to see, please let us know. :-)

  12. Hello,

    I’m very interested in learning about the shielding the case will provide.

    Have you considered offering the following things (as purchasable “accessories”):
    1) a very well shielded 3″ 3.5mm male-to-male cable?
    2) a super shielded case?

    I opt for convenience and velcro the ZO2 to the back of my phone. A lot of interference is produced by this (much more on my new HTC One than on my old iPhone 4s). Unfortunately, the interference is so bad on the HTC One that I believe I’ll have to remove it from being stuck to the back. Even then, and I’m sure there are many solutions to this issue, it’s likely the ZOn will wind up right next to my phone in my pocket.

    I figure it would be nice to address some accessories to make sure that people get the most out of your new products!

    What do you think?



    1. Because the new enclosure will be made from anodized aluminum, this will significantly help with shielding. However, I’m concerned that your having problems with interference using your ZO2… that shouldn’t be a problem, as we took great care to prevent that from happening. There’s only been 1 other instance of someone complaining about EMI, and after looking into the situation, found out it had to do with an app he was using on his phone. Out of curiosity, do you know which version of ZO2 you have? We have released 3 versions, and it may have to do with which one you have.

      We also started including shielded 3.5mm stereo cables around June 2012, which was after the release of ZO2.3 (can’t remember the exact date). So that tells me you may have a ZO2.1 or 2.2.

  13. Will the ZO3 effectively be the better option if i want a “subwoofer” headphone amp. I understand the ZO2.3 is perfect if you want that extra in your face bass, will the ZO3 still offer this plus more? I will be using it with my westone 3’s. Thanks.

  14. Just as a reminder, the point of ZO3 was not necessarily to give more bass than the ZO2, but to provide the FullSpec technology (treble adjustment), give more power, eliminate gain modes, and reduce noise.

    1. It’s not crossfeed per se. Because of how the technology works, it inherently enhances the soundstaging like crossfeed does, but it’s definitely not the same thing.

      1. At the moment I use the Zo2.3 in LO mode, after a Headstage Arrow which has cross feed. I really enjoy this combination. I am not unhappy with the top end of the ACS T15’s that I have on the end of this combo. In fact I am pretty happy all round.
        It’s always nice to have more!
        Am I going to benefit from the Zo3?

      2. The way that Zo’s provide the speaker stereo throw headphones like crossfeeds, must allways be to prevent the stereo stress..? I think.

  15. Wow, i am very impressed by this, it really is moving the Zo2 along. SVT looks to be better than ever with treble adjustments and i am also pleased to see you can turn the SVT off so you can use as a nice flat amp as well. Power is excellent and alu enclosure finishes off a great package. Great stuff and happy new year Digizoid, can’t wait to get my hands on this!

  16. I’m excited to pre order the zo3! I’m also excited to hear about all the sonic improvements made over my zo2. I’m excited that you’ve gone ahead and used an aluminum enclosure replacing the plastic and rubber coating that faded over time. One question, Is pre order available for international buyers?

    1. All joking aside, I am genuinely looking forward to getting the new ZO3. I already have the ZO2, and I love it, so if the new ZO3 will boast 10x the power of the previous ZOs and have an even deeper bass boost, then I’m going to combine the ZO2 with the new ZO3 for the ultimate bass experience, and just sit back and enjoy the music.

  17. I especially love the low output impedance having heard what kind of toll it can have on low impedance headphones/IEMs (lack of clarity, muddled bass response etc.), your focus on trying to keep the noise levels to minimum with the choice of components and the what seems like a great pick of Film Capacitors.

    Regarding the bass output having less of a roll-off down deep isn’t necessarily always a plus, that depends on the natural response of the headphone/IEM itself. As an experienced masterer of Hardstyle music with over 300+ tracks mastered, I often cut slightly down deep <25Hz leading to a punchier & more impactful bass response leaving more headroom for the critical range especially 50 – 80Hz. I tend to prefer punchy/impactful/tight bass characteristic over a too rumbly deep bass. I hope ZO3 will deliver that. :)

    Hopefully the ZO3 will also be more balanced sounding at the lowest level treble contour level than ZO2.3 that had a bit of a V-shape response. As a long-time headphone enthusiast I value the midrange highly and don't want it to get pushed behind the treble and it should have reasonable amount of body to it. Whatever is the case, I'm anxious to give the ZO3 a try! =)

  18. I have two ZO2 and I like very much the new treble selector. I hope that this would not be rolled like the previous.
    Also I would know the output power at different HP impedance and if it will drive the orthos like the Hifimam he-500.

    1. If you’re referring to how the bass slightly rolled off on the previous ZOs, then yes, ZO3 won’t have quite the same amount of rolloff (i.e., the bass will be deeper). Some rolloff is required though to keep the smaller-sized speakers found in headphones/IEMs from distorting.

      In regards to the output power… I don’t have exact specs to give you at the moment; however, the output power of the ZO3 is about 10x that of previous ZOs, so rest assured, it will definitely be able to power anything you throw at it!

  19. Wow this has all the improvements I hoped for and more. 2Vrms input… single gain level… lower output impedance… love all of this. Very interested to find out what the full SVT sounds like. MicroUSB is great too, I wish more companies would use it.

    My only concern is the second flat response amp. I know level-0 ZO2 was not flat, but I’ve always had a higher-end transparent amp for that purpose anyway so I didn’t mind. I hope the ZO3’s size isn’t larger, or quality of other parts weren’t lowered to compromise cost, for a part I may not ever use.

    Very excited to get my hands on one — any plans for early access or preorder?

    1. We’re excited to hear you’re excited! LOL!

      The size of the ZO3 is actually going to be the same – if not a little smaller than the previous ZOs! And no, none of the other parts were compromised – as a a matter of fact, everything has been upgraded in the ZO3.

      We will be taking pre-orders as soon as we start production. We don’t have an exact date yet, but will definitely keep everyone updated as the time nears! =)

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