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).
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.