JDS Labs Atom Stack 2 Review: Small Desktop, Big Sound

Building a clean, capable desktop audio rig without spending a fortune has always been JDS Labs‘ calling card, and the Atom Amp 2 paired with its matching Atom DAC 2 continues that tradition. Together they form the JDS Labs Atom Stack 2, a two-box combo that converts digital audio and then drives headphones or powered speakers with a level of polish that punches well above its modest footprint. This review looks at both units as a system, since that is how most buyers will actually use them.

JDS Labs has spent years refining a formula built on measured performance and straightforward design, rather than chasing trends or gimmicks. The original Atom+ series earned a loyal following among headphone enthusiasts for its transparency and value, and the second-generation Atom Amp 2 and Atom DAC 2 build directly on that reputation with sturdier construction and a handful of genuinely useful upgrades.

What follows is a detailed look at how the Atom Stack 2 is built, what it offers on paper, and how it behaves in day-to-day listening. Readers considering a first proper desktop amp and DAC, or an upgrade from an ageing all-in-one solution, will find plenty here to help make that decision.

Design and Functionality

Both units in the Atom Stack 2 share a compact footprint that keeps desk clutter to a minimum. The Atom DAC 2 measures roughly 131 by 130 by 34 millimetres and tips the scales at around 425 grams, noticeably heavier than the plastic-shelled units that came before it thanks to its new aluminium chassis.

That shift to metal is one of the most welcome changes in this second generation. The anodised aluminium enclosure gives both the amp and DAC a reassuring density and rigidity, and it immediately feels like a step up from the original Atom+ range in terms of perceived quality.

On the Atom Amp 2, the front panel houses a chunkier, easier to grip volume knob along with both 6.35mm and 4.4mm headphone outputs. Having both a standard quarter-inch jack and a balanced 4.4mm connector on the same unit is a genuinely practical touch, since it means listeners are not locked into a single cable standard as their headphone collection grows.

That volume knob is paired with hand matched potentiometers, which JDS Labs uses to keep channel balance tight even at low listening volumes. It is a small detail, but anyone who has dealt with an amp that favours one ear slightly at quiet levels will appreciate the attention paid here.

Around the back of the Atom Amp 2 sit dual inputs, covering both 3.5mm and RCA connections, with a front-accessible switch to flick between sources. This effectively lets the amp double as a small switcher, useful for anyone running both a phone or portable player and a desktop source into the same rig.

The Atom Amp 2 also includes RCA preamp outputs, so unplugging headphones from the front jack redirects the volume knob’s control to a connected pair of powered speakers. It is a feature that turns the amp into a compact preamp for a desktop monitor setup, adding real flexibility without extra cost.

A dual gain switch on the Atom Amp 2 lets listeners choose between a low gain setting of 1.0x, tuned for sensitive in-ear monitors, and a higher gain setting suited to power-hungry full-size headphones. This kind of flexibility matters for anyone who owns both efficient IEMs and demanding planar magnetic headphones.

Internally, the amp relies on a four-layer, star grounded circuit board layout paired with octo-buffer output stages, a combination JDS Labs credits for the lowest noise floor of any Atom amplifier to date. Failsafe DC protection is also built in, guarding connected headphones against damage in the event of a fault.

The Atom DAC 2 follows a similar design language, with a front panel input switch for toggling between USB and optical sources and the brand’s now familiar illuminated ring around the volume area, which glows softly and evenly rather than distractingly.

Around the back of the DAC sit RCA line outputs, a USB-C input, an optical digital input, a 15VAC barrel power socket, and a discreetly placed power switch. Moving to USB-C from the previous USB-B connector is a sensible modernisation that brings the DAC in line with current cables and accessories.

One particularly thoughtful design choice is the alignment of the RCA connections between the Atom DAC 2 and Atom Amp 2, which lets the two units sit side by side and be joined with genuinely short interconnects. It sounds minor, but it keeps cable clutter down and reinforces the sense that these two products were designed to live together.

Packaging remains refreshingly no-nonsense, arriving in simple cardboard boxes rather than anything overly elaborate. Inside, buyers get a new USB Type A to Type C cable fitted with a ferrite core to help suppress noise and jitter, along with the usual stamped inspection card that JDS Labs includes as a small but reassuring quality control signature.

Australian buyers can select the appropriate power adapter for the Atom DAC 2 at checkout, with a 220 to 240 volt, Type I option built specifically for local power outlets, so there is no need to hunt down a separate adapter or converter after purchase.

Both the Atom Amp 2 and Atom DAC 2 are eligible for free custom engraving on their anodised surfaces, letting owners add personal text or artwork through the ordering process. It is a nice touch for anyone who wants their desktop gear to feel a little more personalised without paying extra.

Every element of the design, from the shared footprint to the matched RCA spacing and the consistent aluminium finish, points to a stack that was clearly engineered to be used as a pair. Backing all of this is a two-year transferable warranty on both units, giving buyers confidence that JDS Labs stands behind the build quality it has invested in.

Key Features

The headline feature of the Atom Amp 2 is its power delivery. Its octo-buffer output stage produces more than 2600 milliwatts, or 2.6 watts, per channel, which is a substantial amount of clean headroom for an amp in this class and comfortably exceeds what most headphones will ever need.

That power is delivered without the distortion or grain that can creep in when cheaper amplifiers are pushed hard. Even demanding planar magnetic headphones, which typically need more current to sound their best, are well within the Atom Amp 2’s comfort zone.

The dual gain system is worth highlighting again here as a genuine feature rather than a footnote. Low gain sits at a precise 1.0x multiplication, ideal for sensitive in-ear monitors where noise and channel imbalance are easy to hear, while high gain is tailored to work with the Atom DAC 2’s 2VRMS output to properly drive full-size headphones.

Dual inputs and dual outputs mean the Atom Amp 2 effectively replaces what would otherwise require a separate amplifier and preamp. Two sources can be connected simultaneously, selected at the press of a button, while the front panel offers both a standard 6.35mm jack and a 4.4mm balanced output for headphones.

The RCA preamp output doubles as a volume-controlled feed for active speakers, extending the amp’s usefulness beyond headphone listening into a broader desktop audio setup. This kind of dual-purpose design is unusual at this level and adds genuine long-term value.

On the digital side, the Atom DAC 2 is built around a well proven ESS 9018K2M DAC chip supported by a trans-impedance stage using OPA1692 operational amplifiers, a combination JDS Labs has refined across several product generations to squeeze out excellent measured performance.

Frequency response across the audible 20Hz to 20kHz range sits within plus or minus 0.12dB, essentially ruler flat, while total harmonic distortion plus noise stays below 0.0004 percent across the same range, numbers that put the Atom DAC 2 firmly in audiophile territory.

Signal to noise ratio comes in at 117dB and dynamic range, measured to the AES17 standard with A-weighting, reaches 119dB. SINAD at 1kHz measures 113dB, a figure that reflects just how little the DAC adds or subtracts from the original recording.

USB jitter components at 12kHz are suppressed to 129dB, aided by the ferrite core fitted to the included USB cable, which helps keep digital noise from bleeding into the analogue output stage.

The Atom DAC 2 supports upgradeable firmware through its XMOS USB controller, along with UAC1 and UAC2 modes, optical input, RCA output, and a USB-C connection capable of handling PCM audio up to 32-bit, 384kHz. A UAC1 fallback cable is available separately for anyone wanting to use the DAC with consoles like a PlayStation 5 or Nintendo Switch.

An auto-standby feature automatically powers down the DAC’s light ring and digital-to-analogue circuitry after 15 minutes of inactivity, then wakes it again within milliseconds once audio resumes, a sensible touch for anyone leaving the stack connected around the clock.

The table below summarises the core specifications of both units for quick reference.

Bundling the two units together as a stack makes practical sense given the matched RCA spacing, the shared aluminium finish, and the deliberate pairing of the DAC’s 2VRMS output with the amp’s high gain setting. Buying them as a matched pair, rather than mixing brands, removes a lot of the guesswork that comes with building a desktop system piece by piece.

Both products are backed by the same two-year transferable warranty, which is a meaningful reassurance at this end of the market and reflects the confidence JDS Labs has in its own build quality, engineering and internal quality inspection process referenced by the stamped card included in the box.

Experience Using the Product and Performance

Setting up the Atom Stack 2 is refreshingly simple. Connecting the Atom DAC 2 to a computer via the included USB-C cable and then linking it to the Atom Amp 2 with a pair of short RCA interconnects takes only a few minutes, and the aligned RCA sockets on both units make cable routing tidy from the outset.

Powering on both units for the first time, the build quality is immediately obvious. The aluminium chassis feels dense and cool to the touch, and the front panel controls on the Atom Amp 2 move with a satisfying, precise action rather than the looser feel sometimes found on cheaper amplifiers.

Starting with a pair of efficient in-ear monitors on the low gain setting reveals just how quiet the Atom Amp 2’s noise floor really is. There is no audible hiss even at higher volume positions, which matters a great deal for anyone using sensitive IEMs where background noise is usually the first thing to give away a lesser amplifier.

Switching to a set of full-size, power-hungry planar magnetic headphones and flicking the gain switch to high shows off the other side of the Atom Amp 2’s character. There is a genuine sense of ease and headroom, with dynamic swings in orchestral or electronic tracks handled without strain or compression.

The tonal signature across both units leans transparent rather than warm or coloured. Vocals sit forward and clear, cymbals and high frequency detail are rendered without harshness, and bass extension feels tight and controlled rather than bloated, a sign that the amp is simply getting out of the way of the source material.

Testing the DAC on its own, feeding a pair of active studio monitors directly, confirms that same transparent character. It reproduces whatever is fed into it with minimal added colouration, making it an easy DAC to recommend regardless of which amplifier or powered speakers a listener eventually pairs it with.Streaming lossless FLAC files from a laptop over USB-C produces a noticeably cleaner, more detailed presentation than most onboard laptop audio, with a wider sense of stereo separation and more texture in busier mixes. This is exactly the kind of upgrade a first-time buyer moving away from built-in audio should expect.

Connecting the Atom DAC 2 via its optical input to a television opens up another practical use case, letting the stack double as a clean audio path for movies and games without needing to route everything through a computer. Switching between USB and optical sources with the front panel button is quick and reliable.

Gaming sessions benefit from the amp’s low noise floor and ample power reserve, particularly with headsets that demand a bit more current to sound their best. Positional cues in competitive titles come through with good clarity, and there is no audible strain even when volume is pushed higher during intense moments.

The preamp output on the Atom Amp 2 was tested by connecting it to a pair of powered desktop speakers, and the volume knob’s control over speaker level feels smooth and linear across its entire range. This effectively turns the amp into a compact preamp when headphones are unplugged, adding genuine flexibility to a desk setup.

The auto-standby feature on the Atom DAC 2 works exactly as described in daily use, dimming its light ring and dropping into standby after roughly 15 minutes without playback, then springing back to life almost instantly once audio resumes. It is a subtle feature but a welcome one for anyone leaving the stack powered on for long stretches.

Switching between the dual inputs on the Atom Amp 2, using both a phone connected via 3.5mm and a desktop source via RCA, works exactly as advertised, with the front switch cleanly toggling between the two without any audible pop or delay.

Long listening sessions across several hours reveal no heat concerns from either unit, with both chassis staying comfortably cool despite the Atom Amp 2’s relatively high power output on tap. This speaks well of the efficiency of the octo-buffer design.

Comparing the Atom DAC 2 side by side with the earlier Atom+ generation DAC, run through the same active monitors, reveals essentially no perceptible difference in core sound signature. What has changed is the build quality, the USB-C connector, and small refinements to power efficiency, rather than a dramatic sonic overhaul, which suggests JDS Labs was already very close to its target performance with the previous generation.

Pairing the Atom DAC 2 with third-party amplifiers rather than its matching Atom Amp 2 also works cleanly, confirming the DAC’s transparent, source-neutral character makes it a flexible foundation for listeners who already own an amplifier they are happy with.

The custom engraving option adds a personal touch that is easy to overlook until it arrives. Having a name, short phrase or simple piece of artwork etched into the aluminium top plate makes the unit feel less like an off-the-shelf commodity and more like a piece of desk gear worth showing off.

Volume control precision stands out during quieter listening sessions late at night, where the hand matched potentiometers keep both channels balanced even a few degrees off the zero position, avoiding the lopsided imaging that can plague cheaper volume pots at low levels.

Running a mix of genres, from densely layered electronic production to sparse acoustic recordings, highlights how consistently neutral the stack remains. Nothing is exaggerated or smoothed over, which makes it easier to hear the actual character of different headphones connected to it.

Swapping headphones between a bright, detail-forward pair and a warmer, bass-heavy pair demonstrates the amp’s ability to simply pass through each headphone’s natural tuning rather than imposing its own signature on top, a hallmark of a well-executed transparent design.

Using the stack with a turntable connected through a phono preamp into the Atom Amp 2’s RCA input works smoothly as well, giving vinyl listeners another practical way to bring their turntable into a modern desktop chain without adding extra boxes.

The dual 6.35mm and 4.4mm headphone outputs mean switching between a standard cabled headphone and a balanced cable equipped pair takes seconds, without needing an adaptor cluttering the front panel.

Day to day reliability across an extended testing period shows no dropouts, no unexpected resets, and no issues with the DC protection circuit falsely triggering, all of which suggests a mature, well engineered product rather than a rushed refresh.

The weight and density of both units mean neither one slides around on the desk when cables are plugged or unplugged, a small but appreciated practical benefit of the move to an aluminium chassis.

Feedback from other Atom Stack 2 owners echoes much of this experience, with frequent mentions of the stack bringing power-hungry headphones to life and running reliably for months at a time without any performance issues.

Some owners have noted that the DAC’s light ring is quite bright, particularly in darkened rooms during late-night gaming or movie sessions, which is worth flagging for anyone sensitive to ambient light near their monitor.

JDS Labs’ customer support has also been highlighted positively by buyers dealing with minor fulfilment issues, such as a missing cable, with quick response times and fair resolutions offered without hassle.

Running the Atom Amp 2 on its high gain setting with the Atom DAC 2’s 2VRMS output shows the two units were clearly tuned to complement one another, with the amp receiving just enough signal to reach its full power potential without overdriving the input stage.

For anyone stepping up from a basic USB dongle DAC or a laptop’s built-in headphone jack, the improvement in clarity, dynamic range and outright power is immediately audible, even on a first listen with familiar tracks.

Enthusiasts who already own more expensive separates may find the improvement less dramatic, but the Atom Stack 2 still holds its own as a reference-quality baseline against which pricier gear can be judged.

Across every test scenario, from gaming and movies to critical music listening and use as a speaker preamp, the stack behaves consistently and predictably, which is precisely what a desktop audio setup should deliver.

Living with the Atom Stack 2 for an extended period reinforces the sense that this is gear built to simply work, day after day, without drawing attention to itself beyond the occasional compliment on its understated looks.

Conclusion

The JDS Labs Atom Stack 2 succeeds by refining an already well regarded formula rather than reinventing it. The move to aluminium chassis on both the Atom Amp 2 and Atom DAC 2, combined with genuinely useful additions like dual gain, dual inputs, preamp outputs and a modern USB-C connection, makes this a meaningfully better package than the generation it replaces.

Sound quality remains the star of the show, with a transparent, low noise presentation that lets connected headphones and speakers show their true character rather than being coloured by the source gear. Whether driving efficient IEMs on low gain or demanding planar headphones on high gain, the stack has power and composure to spare.

Buyers who value flexibility will appreciate the dual inputs, RCA preamp output, optical connectivity and custom engraving option, all of which extend the stack’s usefulness well beyond a simple headphone amp and DAC combo. The two-year transferable warranty adds further peace of mind for what is intended to be a long-term desktop companion.

For anyone building a first proper desktop audio setup, or looking to replace an ageing all-in-one solution, the Atom Stack 2 is an easy recommendation. It brings serious measured performance, thoughtful design touches and genuine everyday flexibility together in a compact, well built package that should satisfy casual listeners and dedicated audiophiles alike.