Home » Recording Resources » Featured Reviews » SEPTEMBER 2020: SPL Mercury Mastering DA Converter

D/A conversion on 120v rails? Yes!

Review by Justin Perkins


Earlier this year, SPL (Sound Performance Lab) started shipping its new Mercury Mastering DA Converter, a mastering grade digital-
to-analog converter with phenomenal German build quality that’s available in red or black. It’s designed for use as a main monitoring converter, to listen to various sources in your studio or to feed an analog mastering chain—not at the same time of course, but I tried it in both scenarios, and here’s what I found.

A 120v Rail Converter

Mercury is built on the unique 120v DC Audio Rail Technology found in most SPL products, providing the unit with exceptional headroom and dynamic range. Conversion is handled by AKM Velvet-Sound® technology, with sampling rates up to 32-bit / 768 kHz, and Direct Stream Digital up to DSD4. From an audiophile perspective, Mercury is future proofed for many years to come.

Digital Ins

Mercury makes for a high-quality digital monitoring hub, with two AES/EBU inputs (one of which supports AES dual wire for sample rates up to 384 kHz), two S/PDIF connections, two TOSLINK connections, and USB for use as an audio interface.

Big Simple Buttons

One thing I love about Mercury is the big and simple buttons for changing what source is feeding the DAC. There are no confusing menus to scroll through, or special tricks needed to access all the options and features. You can pretty much start using this thing right out of the box without reading the manual (the opposite of another converter/interface I happen to be reviewing right now).

There’s a very thoughtful MUTE button for those who are using this as a monitor controller or guarding against feedback loops when configuring your routing. It also has a big button to change the clock sync source, and unlike a few other converters I own, you can see the sample rate and additional info on the bright, clear, illuminated screen from a distance, to be sure nothing is amiss.

Mercury is very responsive to sample rate and source changes with no significant or bothersome lag. Everything is very instant and smooth, with no fighting or waiting for it to do what you want it to do.

SPL Mercury front

SPL Mercury back


The Backside

The backside features classic SPL jack labeling that can be read right side up or upside down, something I’ve always loved about SPL gear.\

Mercury features two sets of stereo outputs. One set is fixed, and the other is variable, controlled by a pot on the front and perfect for adjusting the speaker level when using Mercury as a monitor controller. All attenuation is done in the analog realm rather than digitally, thus avoiding bit depth discrepancies due to digital attenuation—a very clever and thoughtful design.\Use the fixed full-level outputs if you plan to use Mercury with a monitor controller or mastering desk. At first, I thought having separate jacks for the fixed and variable outputs was a strange choice, but now I see why it makes sense.

In Use

I found Mercury extremely clear sounding, even when playing back very loudly mastered material. Some converters struggle when they are pushed to the extreme top end of the digital loudness scale. However, Mercury always sounded solid and detailed.

Whether streaming hi-resolution music from TIDAL, DSD tracks from J River Media Center, or recent mastering projects I’ve been working on, everything sounded very pleasing. Clear and precise, but not fatiguing or misleading. I also did a few ‘in the box’ mastering sessions from my home setup using the Mercury for monitoring, and I found it very easy and enjoyable to work with. Most of the projects I used it on were approved on version one, so that’s a very good sign.

While I’m used to having a monitor controller with a DAC built right in (Crane Song Avocet IIA, Grace m905), I could certainly get used to the Mercury connected to a high-quality analog monitor controller instead.

In the Main Room

At my main studio, I used Mercury in my analog insert switcher as one of three DAC options to feed my analog mastering chain. Typically, my options are a Crane Song HEDD Quantum, Dangerous Music Convert-2, and a Prism Lyra 2. The Prism is my least used of the three, so I put the SPL in its place to compare with the others.

For setup, Mercury offers very easy calibration at the press of a button, instead of a buried trim pot on the back. Mercury starts at 0 dBFS = 14 dBu, followed by 15, 16, 17, 18, 20, 22 and finally 24dBu.

The reason I have multiple DAC choices
is, I’ve found that even with high-end converters, usually one of them has a slight sonic advantage over the others depending on the source material. For a particular song, some are a little wider, some deeper, some brighter, etc. As I’m dialing in the settings for a project, I can seamlessly change DAC and ADC
options while the music is playing, finding which one works best for a given song.

While I found Mercury to easily be in the same league as my other DAC options, I did find it to be just slightly on the brighter side of things. For songs that were already leaning bright, the Mercury wasn’t my first choice, but for songs that were a little dull or murky, those sounded great coming out of the Mercury converters. Note that I’m speaking in mastering terms, so I’m not talking about a huge tonal swing here. I’m talking very much on the subtle end of the spectrum. If this were my only DAC for feeding my analog chain, I’d be totally happy. I’m just a little neurotic and prefer to have multiple DAC options for this.

Shortly after using Mercury, I noticed an internet forum comment, where a user had the complete opposite observation about the sound of Mercury. They felt it leaned a little dark compared to their usual DAC. Make of that what you will.


Mercury makes for a fantastic DAC/interface for monitoring in mastering rooms and high-end mixing studios. Though it might be overkill with all the input options, it also makes for a fantastic straight-ahead DAC to feed an analog mastering chain as well. Plus, If you’re starting to get requests to master from DSD files, Mercury can play them.

SPL is known for its exceptional build and sound quality, and the Mercury Mastering DA Converter is no exception.


Price: $2999  

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