HeadAmp Pico & AMB Gamma2 (with other comparisons)

On one side of the ring is the long time favorite DAC from HeadAmp, the Pico DAC. On the other side of the ring is the latest DAC from AMB Labs, the Gamma2. When you put them side by side, it becomes clear that physically, they should belong to different weight class. The Pico is small and very utilitarian. It’s only slightly larger than the Dr. DAC Nano, and it’s very much plug and play. You have a USB input on the back, and two pairs of analog out on the front: RCAs or a 3.5mm jack.

The Gamma2, while remain small enough for desktop use, is actually more than twice the size of the Pico. It comes with an abundance of interface, USB and S/PDIF inputs, both RCA and 3.5mm analog outs, an S/PDIF digital out, external power supply input, an input selector, an anti-clipping and digital filter switches. Though the Gamma2 runs fine out of USB power, the use of an external power supply is recommended, hence there is an additional bulk from the Sigma25 power supply unit (the Sigma25, according to measurements done by Ti Kan, it contributes to a lower noise level).

The Pico in all its simplicity.


USB input on the back. Notice that the paint job is not as smooth on the back (around the HeadAmp logo).


The Gamma2 with Toslink and Coaxial digital out. Anti clipping, digital filter and input selector switch out front, as well as the analog output from the Gamma1.


Left to right: 5V 300mA DC input (optional), Toslink and Coaxial digital inputs, RCA and 3.5mm analog outputs, USB digital input.


Why put them against each other? Well, many reasons. We’re talking about the Pico DAC here, which doesn’t come with an amplifier, and sells for $349 directly from HeadAmp. The Gamma2 is also purely a DAC unit without an amplifier. It is a DIY design, and the parts will cost you roughly $200+ including the case, and close to $300 if you decide to build the Sigma25 power supply unit. So I thought, close enough in terms of price, and it should give an advantage to the Gamma2, since DIY builds can often compete with commercial builds 2-3 times the price.

What’s more, both DACs are also similar in the sense that they take a 16/48 signal from the USB, and upsample it to 24/96 with an asynchronous sample rate converter (ASRC) chip. They are so similar, in fact, that they use the same chips: PCM2707 USB controller, Wolfson WM8740 (8741 and 8742 also an option in the Gamma2), and an AD1896 ASRC chip (Burr Brown/TI’s SRC4192 chip also an option in the Gamma2). This particular Gamma2 comes with the WM8741 which provides three different digital filters (see details later) and an anti-clipping mode, as well as the SRC4192 ASRC chip. Well, I don’t know if it’s the WM8741 that sounds different from the WM8740, or the AD1896 to the SRC4192, because as similar as the two DACs are, the Gamma2 and the HeadAmp Pico is totally different in terms of sound output.

The comparison is done with a MacPro as the transport, Itunes, playing WAV files from redbook CDs. I don’t use any 24bit files, since the DACs only support 16bit from the USB controller, meaning that if I use 24bit files, it’ll be converted down to 16bit, before later being upsampled back to 24bit. As usual, I’m using the same TPA6120 that I’ve been using for all my recent DAC reviews, balanced output to the HD800.

3.2/5 - (4 votes)


  • Reply April 29, 2010


    Nice review!

    I wanted to point out a review/discussion on Head-fi forums on Hud-MX1.

    The reviewer "audiofil" has done some op-amp rolling, from his findings for AD797BRZ x 2 (SOIC pckg. on BD) – I am guessing may be the sound signature is simillar to the coloration of PICO you are referring to.

    • Reply April 29, 2010


      Thanks for the link!
      Reading the author's comments, he seems to really like the AD797BRZ, but he didn't say enough about the sound that I really can't deduce if it's indeed the "Pico" sound.

      I was surprised to hear his comments about the Gamma2, which he found to be more refined, warmer, and fuller sounding. I do agree that the Gamma2 is more engaging and that it has better PRaT than the Audinst HUD-MX1.

  • Reply April 29, 2010


    Hi Mike, sorry to hijack this but I don't know your personal contact. Anyway, an audiophile shop near me has stocked up on Styleaudio Carat-Ruby MkII unit for 340USD. I'm going to audition it this weekend. In case I like it and decide to get it, I might have to push the purchase to next month as someone is going to get annoying if I am to buy it this month. Some comment on specs:

    The Topaz is the 2009 version of the original Ruby and in turn Ruby MkII is the 2010 version, what has changed from the Topaz:

    – Bigger DC to DC converter unit, leading to bigger depth of the entire unit itself (13cm instead of 12.5cm).

    – 24K gold plating PCB.

    – Lineout stage output opamp: changed from AD817 to OPA604.

    – Accept 24bit/96Khz through USB instead of 16bit/48Khz thanks to Tenor chip.

    – Uses PCM1796 instead of PCM1792A, a downgrade in spec but who knows.

    – Free voltage adapter with detachable power cord for different standards. IOW you can use the ruby mkII anywhere as long as you have the right power cable.

  • Reply May 2, 2010


    Nice review, it's something I've been wondering about a while.

    Like you note, a lot of the ICs used in the two DACs are the same, but interesting that you found a significant difference between the y2 and the Pico DAC. It might be useful to specify which op-amp was used in your y2's output filter stage (the OPA2365 option is said to be the same used in the Pico DAC section, vs the AD8656) as that could contribute to the sound signature.

    Personally one of the reasons I chose the y2 over the Pico was for the additional digital inputs to run off CD players.

    • Reply May 3, 2010


      Hi Jeremy,
      Sorry for the slow reply as I have to talk to the builder to get that information. This particular Gamma2 uses the AD8656.

      Yes, it is a pity that the Pico doesn't come with S/PDIF inputs for hooking up to CD Players. 🙁

  • Reply May 19, 2010


    Wow this is a really profound comparison between those DACs. I never thought Pico would be that good! Coz I've always assumed that DIY will always rule over branded stuffs twice as its price or even more and on the other side Pico would easily get beaten by a DIY half its price.

    Thanks for the great comparison!

    Now it's in between Pico and Audinst for me. 😀

  • Reply May 26, 2010


    Interesting results Mike. My y2 has the OPA2365, but is otherwise identical to yours (SRC4192, WM8471, external Linear Reg PSU).

    I had a chance to compare the y2 and Pico side by side and found little difference (as did others in the setting). I used my HD800 with the M^3/Sigma-11 for the comparison. The subtle differences that I did find favoured the y2 and, surprisingly, some things were actually the opposite of what you've said. For instance, there was more bass weight/punch with the y2, a little smoother upper-midrange/treble and a wider soundstage (depth was about equal). Other than that, there was a striking similarity in sound signatures of both DACs.

    Perhaps opamps make a noticeable difference in the y2…who knows.

    Oh BTW, I found a noticeable improvement from using the coaxial input instead of USB…but I won't get into that now. I haven't tried optical yet.

    • Reply May 26, 2010


      Thanks for sharing your findings Shahrose. Some contradictions in audio can be very puzzling to me. Everything that I heard is what I wrote on the review, and clearly we found different things. Maybe you have build a lemon Gamma2, Shahrose. Just kidding. 😀

      • Reply May 26, 2010


        Tell that to MisterX, who built it for me. :p

        • Reply May 26, 2010


          MisterX? Sshhhh, don't tell him I said that. 😛

  • Reply July 3, 2010


    It's pretty obvious which one of you two has a lemon Y2 build. 😉

  • Reply October 12, 2010


    Hi Mike,

    Have you tried connecting the PICO DAC

    to an amp using RCA male to male couplers?

    If so, are there any particular brands

    you'd recommend or will any coupler be fine?

    I'm sorry if I missed it in the review.

    • Reply October 12, 2010


      Hi JJ, a local audio guy has been supplying my needs of interconnects. It's pretty high quality, but since its his own build, I don't think it'd be easy for you to get one as he doesn't even have an email. Branded cables, you know these RCA to RCA cables run anywhere from $1 to $1,000 right? 🙂 Just buy a nice looking one at a decent price and enjoy the system for now. 🙂

  • Reply March 9, 2011



    the problem is with the ASRC chip. The AD1896 ASRC chip has a better jitter rejection than the SRC4192; its internal filtering also makes a difference. Getting the AD1896 will make this a fairer comparison.

    Internal filters make a lot of differences in DACs.

    • Reply March 10, 2011


      Thanks for chiming in, KK.

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