Digital audio has always been a quest to capture the “magic” of analogue audio. We’ve come a long way since CDs were first released, but along the way there have been attempts to simplify circuits and reduce costs resulting in some amazing leaps in sound quality and potentially some drift away from the smoothness of analogue.

For the purpose of this review I think it’s important to declare myself as a digital realist rather than an analogue purist. I admire those who enjoy the ritual of turntables and vinyl, but it just doesn’t suit my lifestyle given how good digital audio can be. The slight trade-offs have been worth it for me and I enjoy the chase for the ultimate (relatively affordable) digital setup.

All this preamble leads me to the topic of this review, the Schiit Gungnir Multibit DAC (also known as Gumby). When Philips first created a DAC back when they worked with Sony on the first digital audio standards, they used a multibit design. Multibit designs are often considered to sound better than the more modern single-bit (delta-sigma) technologies, but MB DACs are generally considered to be more expensive and more complicated to build in order to reach the same (or better) quality than a modern delta-sigma DAC.

Multibit DACs have remained in the shadows (often the very expensive shadows) of digital audio as the popularity and proliferation of delta-sigma (DS) DACs increased. Recently though, MB DACs have enjoyed a resurgence led in no small part by Schiit, the pun-demanding US-based brand known for their irreverent approach to marketing and bold approach to reasonably priced amps and DACs designed to provide unreasonable levels of performance.

I had listened to Schiit gear before and hadn’t been blown away, but I was so intrigued by the reviews I read of their multibit DACs that I got my hands on a Gumby having never listened to one. Before I tell you all about it, let’s clarify (slightly) the difference between Multibit and Delta-Sigma processing.

Multibit & Delta-Sigma: What’s the difference?

OK, time for a massive disclaimer. What follows here may be the most dumbed-down explanation of DAC technology you’ll ever read. I’m adapting and further simplifying a great article from the MSB website in an attempt to explain the differences in ways that will make sense to others like me who don’t have a mind for binary data and similarly mathematical explanations of digital audio.

In the simplest of terms, a DAC receives an analogue signal (fluctuating voltages), but those fluctuating voltages represent binary on/off pulses. The DAC needs to look at the fluctuations of the incoming signal and translate that from a series of on/off pulses into something resembling the much more graduated (wave-like) voltages of an analogue audio signal.

In the most basic terms, a delta-sigma DAC reproduces each sample in the analogue audio signal by producing a series of “pulses”. This multiple-pulse approach is why delta-sigma DACs are sometimes referred to as oversampling DACs – they break up a single sample into many samples or pulses of voltage. Due to the speed at which music is sampled (44,100 samples per second for CD audio), the available time to produce all these pulses is limited so the initial stage output from a delta-sigma DAC creates a jagged representation of the actual signal (think about trying to make a curved wall using regular rectangular bricks). Because of this, delta-sigma DACs employ heavy filtering to measure the “jaggedness” or error (which is predictable) and reconstruct the “correct” waveform. The better the filter, the better the sound, but it’s always an estimation of the actual waveform and is never actually 100% accurate.

Multibit DACs work differently by using a series of resistors to output a single variable voltage (not multiple pulses of the same voltage). For this reason, multibit DACs are sometimes referred to as non-oversampling (NOS) DACs because they reproduce each sample just once with a variable voltage. The resulting output from a multibit DAC more closely represents the actual waveform rather than the jagged version produced by a DS DAC (think about building a curved wall with clay instead of bricks). Now that might sound like an easy decision that multibit is clearly better, but there’s a problem. If any of the resistors used to produce the variable voltages are slightly out of calibration then the whole signal can be messed up. Add to that the variation in resistor performance depending on factors such as their build quality and even operating temperature and you quickly see that MB DACs introduce some very specific challenges of their own. This is why they are generally more expensive than DS DACs.

What I took from all my research was that a multibit DAC will generally sound more musical and natural than a delta-sigma DAC because there’s no need for heavy filtering* to remove the noise and errors created by the jagged waveform created by a DS DAC. However, I also took from my research that I’d have to cough up significantly more money to enjoy those benefits and coming from my already excellent Matrix X-Sabre (delta-sigma) DAC, I wasn’t in any hurry… until the Gumby came along.

* Schiit still employ filtering in their multibit DACs, but the type and degree of filtering required in a MB DAC is quite different as I understand it

Meet Gumby

The Gungnir is Schiit’s second highest performing DAC and, like all but the top shelf Yggdrasil, it comes in both standard (delta-sigma) and multibit guise. You pay about $700 (AUD) extra for the pleasure of multibit technology in a Gungnir and the right to call it a Gumby. For reference, the Matrix X-Sabre that I’ll compare this to later costs roughly the same as the delta-sigma Gungnir so they’re very comparable until the $700 multibit upgrade is added. The question of course is whether it’s $700 well spent.

I won’t go into a lot about the specs of the Gungnir, but here they are:

• DAC chips:  Analog Devices AD5781BRUZ x 4 (2 per channel, hardware balanced configuration)
• Analog stage frequency response: 20Hz-20Khz, +/-0.1dB, 1Hz-200KHz, -1dB
• Maximum output: 4.0V RMS (balanced), 2.0V RMS (single-ended)
• THD: Less than 0.005%, 20Hz-20KHz, at full output
• SNR: > 115dB, referenced to 2V RMS
• Inputs: RCA SPDIF, BNC SPDIF, Optical SPDIF, USB (all up to 24-bit / 192kHz)
• Outputs: One pair XLR balanced, two pairs RCA single-ended
• Power supply: two transformers (one for digital supplies, one for analog supplies) with 8 stages of regulation, including separate local supplies for critical digital and analog sections
• Size: 16″ x 8.75” x 2.25” / 40.6cm x 22.2cm x 5.7cm
• Weight: 11 lbs / 5 kg

Interestingly, the total harmonic distortion produced by the multibit Gungnir is higher than the delta-sigma DAC, but at 0.005% it’s hardly an issue so much as a point of interest. Perhaps the most interesting specification though is the massive attention to detail that has clearly gone towards the power supplies in the Gumby. It’s a big beast – more than twice the size of the X-Sabre, but the extra space has gone to good use by the look of this list with fully balanced operation, multiple power transformers to isolate sensitive circuitry from noise, and plenty of great input and output options for maximum flexibility.

Connections and Compatibility

The Gumby is basically plug and play for all types of connections except USB from a Windows PC (Apple is still plug and play I believe). For Windows users like me, you need to download the drivers first, but my experience is that they install easily and work seamlessly. Other than installing Windows drivers, everything else just works with the Gumby. Connect to SUB, BNC, RCA SPDIF, or optical and deliver any signal up to 192kHz and you’re set. I’ll discuss in the sound quality section how different inputs may vary in terms of sound quality, but there’s no variation in terms of functionality.

There’s a light on the front of the unit at the right hand end that Schiit refer to as the “buy better gear” light. This light will always flash when you first power up the Gumby and I assume it’s to allow the circuits to all initialise because the Gumby won’t create any sound until you hear a little click and the light stops flashing. Given the importance of temperature in multibit DAC operation, this may also be giving the resistors some time to reach an acceptable operating temperature.

In the unlikely event that you have a truly shitty source or cable, the “buy better gear” light (aka the Clock Mode LED) will continue to flash, but the DAC will still work – it’ll just use a different type of reclocking to improve the signal as best it can. The light is more about letting you know that you could be hearing better sound quality if you upgraded the offending gear. Schiit call out the Airport Express as one such culprit that will illuminate the BBG light, but reassure users to rest easy if the gear is not upgrade-able for any reason – just keep on enjoying it, they say.

For outputs, the Gungnir offers one set of XLR outputs for amplifiers with balanced inputs and two sets of RCA outputs for amps with single-ended inputs. All outputs work simultaneously so the Gungnir can happily be a source to multiple amps if you’re like me and have a few different rigs on the go sometimes.

Sample Rates

It’s probably important to address sample rates here because the Schiit DACs don’t do DSD – they only process PCM audio up to 24-bit / 192kHz. Some people will instantly click away at this point and that’s cool. I believe DSD audio can sound really good so I respect people who want DSD-capable DACs. Personally though I have no problems at all letting go of DSD. I have very little DSD audio in my library and can’t honestly say that it is consistently better than well-recorded PCM (WAV / FLAC) audio. Given how beautifully the Gungnir renders PCM audio I have no qualms about it not doing DSD.

To confirm, the Gungnir (Multibit or Delta-Sigma) will handle 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, and 192kHz recordings at either 16-bit or 24-bit. Basically, if it’s a FLAC recording, the Gumby will be fine with it and will sound great!

Sound Quality: This is the Schiit!

When it comes to defining DAC sound quality, the differences in sound tend to come from two places – the ability of the DAC to manage jitter / signal errors and the characteristics of the output stage of the DAC (where it sends the freshly baked analogue signal to the outputs for your amplifier). The sum of the Gumby’s signal conversion and output stage results in a sound that is smooth and perhaps slightly warm. If I use the comparison of the Matrix X-Sabre as a reference point, the Gumby has an almost identical sound signature in that it’s slightly warm and wonderfully musical. Where the Gumby differentiates itself is in the smoothness. Initially, this smoothness was a bit off-putting and had me thinking the Gumby sounded a touch thick and rolled-off, but time and some warm-up soon corrected my initial erroneous impressions and allowed me to hear the Gumby’s true colours.

Sound Impressions

Now that I’m comfortable and used to the Gumby’s sound I can only describe it as the closest thing to true analogue reproduction that I’ve heard to date. The sound is remarkably smooth and nuanced. Details are laid out in a rich landscape of nuance and texture, but there’s none of the glare that many of us are used to in the world of delta-sigma DACs. At first, the lack of glare can be very off-putting if you’re coming from years of DS decoding (like I was), but given a bit of time, the wonders of a well-executed multibit system become abundantly apparent.

When I switch back and forth between the X-Sabre and the Gumby now I am struck by two things:

1. The X-Sabre is still an outstanding DAC and sounds almost identical to the Gumby in all ways (signature, soundstage size, quality of imaging and spatial cues) but one…
2. The Gumby puts the cherry and cream on top by stripping away the final sense of digital haze and letting all of the glorious nuances of every recording shine through

Compared to the slightly digital (by comparison) X-Sabre sound, the Gumby leaves space between each sound by virtue of the lack of digital haze filling the gaps. Each sound is more precisely rendered – probably because the multibit decoding process is getting it more accurate from the get-go and doesn’t require a filter to fill in the blanks. Treble-focussed sounds like cymbal hits have a smoothness that’s beguiling, but isn’t a case of viewing through rose-coloured glasses so much as viewing with no glasses at all. There’s the sense that nothing is getting between the music and your enjoyment when you listen to a Gumby with a nice amplifier and your favourite pair of cans. It’s safe to say that it’s the closest thing I’ve heard to my memories of a nice turntable setup – smooth, detailed and rich, just like a live performance.

Incremental Gains

There are two incremental gains I want to mention here because I think it’s very important to understand them before you dig too deep into your wallet.

Is This Schiit Better?

While I believe you will hear a difference between a DAC like the X-Sabre (i.e. DACs performing in the $1,000-$1,400 range), you shouldn’t upgrade to a Gumby expecting it to transform your entire listening experience. There’s no doubt that I am completely happy with the upgrade from the X-Sabre to the Gumby, but it’s hard to measure the economic value of sound quality improvements and I would hate to lead anyone down the path towards expecting a life-changing upgrade. If this were the Olympic Games, the Gumby would be the gold medal favourite despite being matched up against the best of the best. Other DACs like the X-Sabre are deservedly in the field of contenders, but the Gumby is like Michael Phelps – not always blowing away the competition, but always better.

Maximising the Value of a Gumby

I’ve already covered the fact that there are many input options on the Gumby: USB, optical SPDIF, RCA SPDIF, and BNC. I’m currently writing 2 articles about the pros and cons of the various digital audio interconnect formats and the results have been illuminating. When it comes to the Gumby, it will sound great from a good USB setup, but there is no doubt that different inputs can produce better sound quality. I’m not a technical expert and therefore won’t presume to know how much of the difference is better input circuitry on behalf of the Gumby and how much is a reflection of the pros / cons of each transmission method, but I will detail what I hear on each input:

• The USB input is clearly the least spectacular of the 4 inputs available. It still sounds great, but you’ll hear gains if you can use alternate methods. What holds the USB input back is a degree of jitter / noise that, while not exactly audible, definitely creates a sense of compression in the music. The soundstage seems a bit smaller, there is less sense of space around individual sounds, and the background is less “black”. I can’t stress enough that USB audio with the Gumby still sounds great – it’s just that other inputs sound even better.
• The optical and RCA SPDIF inputs should both be quite similar in performance, but I don’t have a high quality optical cable to properly compare the two so I will tackle this from the angle of the RCA SPDIF. As an aside though, the optical SPDIF with a cheap, old cable was still very slightly preferable to the USB connection even when using AudioQuest JitterBugs and the top-of-the-line AudioQuest Diamond USB cable. Connecting via RCA SPDIF improved on the already excellent USB sound by removing the sense of compression and creating a greater sense of space in the sound overall. There’s also the benefit of slightly smoother treble.
• The top of the tree for input options on the Gumby is definitely the BNC input which takes everything good about the SPDIF sound and further improves on it. All remaining sense of jitter and noise is stripped away and the sound reaches peak levels of smoothness, cleanness, richness of tone, sense of space around sounds and overall size of soundstage. Everything becomes almost holographic in nature to the point that I am now constantly removing my headphones to check if sounds I’m hearing are in the music or in my house. (That’s slightly annoying at times, but so worth it!)

The point I hope I’ve made here is that the Schiit Gungnir Multibit is worth buying regardless of whether you’re going to use USB, SPDIF, or BNC, but if you can find a way to get BNC input you should absolutely go for it. If you’re like me and only have a USB source like a laptop computer, check out my post about upgrading your computer audio without breaking your budget.

Conclusion

This is a tricky conclusion to write because flicking between the X-Sabre and the Gumby tells me that they are in the same league, but there’s no way I’d ever go back to the X-Sabre now that I’ve owned the Gumby for a while (and connected it using BNC). This could be one of those cases where the Gumby perfectly suits my listening preferences thanks to its smooth, fatigue-free and highly musical sound, but don’t equate that with it being overly lush or thick sounding. From my experience, the Gumby is a creator of perfect renditions of life-like auditory experiences. It’s sound is nuanced and detailed with a sense of ambience and soul. It will reveal crappy recordings and will reward great recordings, but either way it will present the best possible rendition of any recording in a manner that’s astoundingly reminiscent of a great vinyl setup.