Parasound Zdac V.2 and Headphone Amp
Roughly two years ago, I spent some time with Parasound's overachieving Zdac. I really enjoyed its warm, inviting tone, not to mention its striking appearanceit reminded me of something from Parasound's upscale Halo line, yet came in at a relatively affordable $475. It was easy to recommend. I've since noticed quite a few positive reviews crop up at various other sites, and although I don't have numbers to prove this theory, I'm fairly certain the Zdac was a big seller for Parasound. So, why mess with a good thing? Alas, the Zdac was recently discontinued. The good news? A refreshed second edition, dubbed Zdac v.2, takes its place. At $549, the new version is exactly $74 more expensive than the outgoing model.
Richard Schram of Parasound tells me the original was so well received that they really didn't dare mess with the core design. Therefore the majority of the guts in this new version remain identical. To recap: we get the same Analog Devices AD1853 DAC chip supported by an AD1895 ASRC, with all inputs being upsampled to 422kHz. The power supply remains a linear design using a relatively large toroidal transformer. Coaxial and optical SPDIF inputs come in through an AKM AK4113 receiver while USB is handled by a Texas Instruments TAS1020B running custom code from Holm Acoustics. It should be noted that this solution is NOT asynchronous, unlike most everything else these days. It relies instead on Holm's custom jitter-scrubbing system which supposedly levels the playing field. Nor does it support the latest whiz-bang features like DSD and 384kHz PCM. In fact, USB tops out at a relatively old-school 24-bit/96kHz, which is a limitation of the USB chipset and could well be a deal breaker for some. The two SPDIF inputs go up to 24/192kHz which may help matters a bit. Then again, most people I've spoken with say CD quality material still makes up 95% of their music library (or more), so perhaps this is no big issue in the grand scheme of things.
While the main DAC itself remains unchanged, Parasound did go to work addressing the various minor complaints leveled at the original model. This includes minor aspects which could have easily been left alonedemonstrating Parasound's dedication to refining this little device to perfection. For example, when the original was purchased in black, it came with unavoidable rack mount holes in the faceplate. The silver version did not, and was more attractive for it. Parasound discovered that most folks were using Zdac in a desktop setup, so now both color options offer the same clean look sans mounting holes. An add-on is in the works which will allow rack placement for those who still desire such a configuration.
The largest change (and of most interest to the InnerFidelity reader) is clearly the headphone amp. Honestly I think Parasound somewhat underestimated the demand for such a thing the first time around. Thus the headphone section was never really the main focus. That approach has changed on this second iteration. Proof of this attitude adjustment can be seen on the front panel of each devicethe first model described itself as "Zdac Digital to Analog Converter" while the refreshed unit says "Zdac v.2 DAC & Headphone Amp". That pretty much tells the story as far as I'm concerned.
Externally, we get a choice of 1/4" or 1/8" jacks this time, instead of being limited to just 1/8" like the first version. On the inside we get a more complex designstill based around the TPA6120A2 driver, but now bolstered by a pair of LM49720 opamps and a larger capacitor array to deliver more current and somewhat higher gain. There's also now a relay in the mix to alleviate the pops I complained about. Output impedance remains at 10 ohms which again is not ideal but not terrible either. This is commonly seen, as the datasheet calls for a series output resistor of at least 10 ohms to increase stability with low impedance loads. Workarounds do exist to bring output impedance closer to an ideal 1 ohm without causing troubleI know of at least 2 other affordable devices having done just that, to their benefit. So, a small opportunity missed, but overall the headphone section is definitely improved. It's actually the exact same circuit which makes an appearance in Parasound's new $2,495 Halo Integrated. How's that for pedigree?
Another key improvement brings us preamp capabilities via analog volume control. In this day and age it's far more typical to see a simple (and lossy) digital volume scheme implemented through the DAC chip. I'm not particularly biased in either direction, and I recognize both types have their drawbacks, but I do think more people tend to appreciate analog solutions when possible. The result is the Zdac v.2 can be a legit source driving an amplifier directly. Or, use it with active monitors for a compact all-in-one desktop solution. Volume control can also be disabled for those who prefer straight DAC functionalityoutputs are very close to the redbook standard at 2.1Vrms for RCA and double that for XLR.
There are plenty of thoughtful touches to be found here. I like the independent knobs for line-out and headphone volume, and I like that the device remembers which input I was using even after a power cycle. It automatically mutes the line-out when a headphone is inserted, which is a somewhat rare feature on a lot of devices I've tried lately...not sure why, as it seems to me that would always be the desired behavior. I also dig having the option to connect my iPad Air to the USB input using a Lightning to USB adapter. I don't recall this being possible with the original model but I could be wrong. At the time it would have been connecting to older Apple products with the 30-pin connector instead of Lightning, but honestly I just never thought to try it. Now that I have, I actually use it surprisingly often.
As Richard Schram mentioned, Parasound didn't want to mess with success, so the DAC portion remains unchanged from the first model. I sent that review unit back long ago but from memory I'd say the new version sounds pretty much identicalwhich I consider a good thing. This is a smooth, fatigue-free device which places listening pleasure ahead of micro-detail overindulgence. It feels right at home whether acting as preamp for my Adam Audio active monitors, as a straight DAC feeding my electrostatic setup, or just driving headphones directly as a compact all-in-one. It's not the most resolving thing I've ever heard but I wouldn't call it overly dull eitherit just places more emphasis on musicality rather than top-down detail retrieval. I could go on and on about how much I enjoy it, but I won't... you can read all about it in my coverage of the original model, as everything I said there still stands.
The thing I want to focus on more is the revised headphone stage. This time around we get beefier output and slightly higher gain which makes it more capableespecially when paired with power-hungry planar magnetic cans. The original Zdac paired best with Sennheiser's HD600, and that classic workhorse still does well on the new version. Same for HD650, K702, and various easy to drive dynamic cans from Sony, AKG, Ultrasone, and Grado. But this time around I had a far better time with planar magnetic models such as the Audeze LCD-2, HiFiMAN HE-500, and Alpha Dogs. There's more grunt involved, more immediacy and full-bodied enthusiasm, while still keeping the slightly laid-back character from the DAC. It's a sound that's easy to love, making all my music sound perhaps subtly better than it normally would. This is an integrated device that I could happily recommend even for those folks who never plan on grabbing an external amp.
Obviously that 10-ohm output impedance won't be ideal in some situationsespecially for IEMs. I tried a few balanced-armature designs and got generally decent results as far as quiet background noise with no hum or hiss. But the frequency interactions were noticeable in most cases, to varying degrees, making each IEM sound different enough to be somewhat bothersome. Casual IEM users may not object to this so much. Unfortunately they likely will notice the bass boost/looseness which tends to accompany a less-than-ideal output impedance. Switching to the HiFiMAN IEMs with their dynamic drivers brought substantially better results. The RE-400 was very enjoyable if slightly warmer than normal, and the old RE-262thanks to its 140+ ohm impedancesounded about as good as I've ever heard it. I would love to see HiFiMAN revisit the idea of higher impedance IEMs now that portable amps and powerful DAPs are more prevalent.
With a design like this, it's difficult to separate the amp section from the DAC which feeds it. If forced to pick traits, I'd say this revised amp is generally neutral, so the final output flavor ends up reflecting the DAC more than the amp itself. Parasound knew what they were doingbeefing up the amp section made for less stumbling with difficult loads, and therefore less unintended coloration. As surprising as it may seem from looking at this little device, it really does sound quite good with something like an HE-500 or even the new HE-560 based on my limited exposure to that model. I'd say HiFiMAN's somewhat brighter presentation plays favorably with the sonic character of the Zdac v.2, as opposed to the darker, richer Audeze house sound. But again, the LCD-2 still sounds quite good overall. Aside from potential impedance mismatching, there is very little to complain about with this built-in amp section.
The Parasound Zdac was already a very enjoyable device. It offered a very "analog" sound in an attractive, relatively affordable package, from a well known and respected brand. The few complaints I had were all minor in scope, yet Parasound saw fit to revamp the designfixing all those issues in the process. Where the original model was a nice DAC with a decent headphone output as a sort of bonus feature, Zdac v.2 is now a very competent all-in-one DAC/preamp/headphone amp solutionfor a mere $74 extra. It may not satisfy those looking for all the latest DSD support, but for "real world" listening it doesn't get much better in this price range.