JDS Labs Atom 2 Stack Review

On this page we’re checking out the JDS Labs Atom AMP 2. If Google took you here directly, click here to go to the start of the article.

JDS Labs Atom AMP 2

After five successful years with their original Atom Amp and Atom DAC, JDS Labs isn’t waiting on the side lines. They’ve introduced the Atom Amp 2 and Atom DAC 2, boasting refinements and upgrades while maintaining the core transparency and value that made the originals popular. They also emphasize that the standard Atom Amp+ and Atom DAC+ aren’t going away. They remain reliable, affordable options at a slightly lower price as the base MSRP of the AMP increased from $99 USD to $129 USD.

According to JDS, the Atom Amp 2 is the best Atom you can own, built in an all-metal chassis with an easier-to-grip knob, featuring both 4.4mm and 6.35mm SE outputs, DC protection, and stereo octo-buffers delivering 2.5x the power of Atom Amp+. Here’s the data:

• Frequency Response, 20Hz-20kHz: +/- 0.01dB
• SINAD @ 2VRMS, 1kHz: 120 dB
• SINAD @ 50mV, 1kHz: 93 dB
• Output Impedance: 0.7 Ω
• Max Continuous Power @ 600Ω: 143 mW (9.28VRMS)
• Max Continuous Power @ 300Ω: 286 mW (9.27VRMS)
• Max Continuous Power @ 150Ω: 570 mW (9.25VRMS)
• Max Continuous Power @ 32Ω: 2.65 Watts (9.22VRMS = 26Vpp)
• Dual Gain 1.0 & 4.7x

So, What’s New?

According to JDS Labs, the Atom Amp 2 takes the Atom line to new heights, doubling the weight with its all-aluminum build and doubling the power compared to the Atom Amp+. SINAD receives a slight boost (120dB) for even cleaner performance, while the noise floor drops significantly due to the octo-buffer output stage. JDS Labs maintains the original’s high-performing input stage and filter but upgrades the gain stage to the OPA1656 for enhanced results. While output impedance increases slightly due to the paralleled buffers, it stays well within a reasonable range. (0.7 ohm). They recommend using headphones with a minimum impedance of 6 ohms. Importantly, JDS Labs continues to use the same custom, hand-matched potentiometers in both amplifiers, ensuring consistent channel balance across the volume range.

Atom+ AMP was already an excellent unit, one of the best desktop headphone amplifiers out there, offering heaps of clean power for a fraction of the average desktop amplifier price. Doubling the power while maintaining the clarity, transparency, and overall ease of use is a no-brainer for me.

Packaging & Accessories

The Atom Amp 2 offers the same familiar unboxing experience as the Atom DAC 2. You get two no-frills cardboard boxes: one for the amp and one for the hefty 16VAC power supply.

In terms of accessories, it’s a bare-bones affair. You’ll find just the essentials: the unit itself, the adapter and the signature-stamped inspection card. While a few extra goodies might have been nice, the emphasis here is clearly on functionality rather than extravagance, to keep the price as competitive as possible.

Design & Build Quality

The Atom Amp 2 is naturally the best companion to the Atom DAC 2. They share the same all-metal construction and design aesthetics. The dimensions of the AMP are 145 x 131 x 34 mm, so the form factor is more or less the same. The switch from injection-molded plastic to aluminum has increased the weight from 260 grams to 454 grams, and I can’t see any assembly problems or housing imperfections, as you’d expect from JDS Labs.

In terms of layout, the AMP 2 has a slightly smaller volume pot with a white LED light ring around it. It matches the Atom DAC 2’s front panel in this detail, and they look great stacked on top of each other. Looking at the right side of the volume pot, we see two spring-loaded push buttons. These are used to change the gain and the input quickly and effortlessly. 

Looking at the left side of the volume knob, we see a 4.4mm and a 6.35mm headphone output. The 4.4mm is purely for convenience, as both outputs are unbalanced. On the back, we find RCA inputs and outputs, a 3.5mm input, and finally, a barrel-type power socket for the 16VAC adapter. A welcome change is the RCA alignment between the Atom 2 DAC and Atom 2 AMP, allowing the use of ultra-short interconnects. The gold-plated plugs and sockets feel solid and well-made. The Atom Amp 2 ticks all the right boxes with its elegant but simple design.

Features

Atom has been one of the most powerful amplifiers under $200 USD for quite some time now. There are little to no competition when it comes to pure performance to power ratio, and now JDS doubled the power output while maintaining the excellent performance. It has extremely low noise and distortion, no clipping and able to dish out whopping 2.65 watts of power to 32 ohm load. 

These are crazy good numbers and it can be used to drive nearly every headphone out there on the market. It also has a very low output impedance, which means that you can use it with sensitive IEMs without any issues. My unit has perfect channel balance throughout the entire volume range, and a low gain of 1.0x is practical when driving sensitive IEMs.

About the 4.4mm headphone output, JDS Labs anticipates a common question: “Does the 4.4mm jack offer balanced output or extra power?” They explain that this notion stems from differential bridged mode circuits, which come with trade-offs like increased noise and distortion. Rest assured, both headphone jacks on the Atom Amp 2 deliver a powerful 26Vpp single-ended output with an impressively low noise floor. However, JDS Labs leaves the door open for a potential differential output amp in the future, saying, “If you want to see a differential output amp, let us know!”

Well, I, for one, would like to see that happening as JDS has been acing anything they put their hands on for a long time. Why not expand the product range?

JDS Labs prioritizes user safety with the inclusion of DC protection in the Atom Amp 2. Standard protection circuits designed for speakers are unsuitable for headphones due to their higher sensitivity. These circuits typically tolerate a voltage threshold much higher than what could damage delicate headphone drivers. The Atom Amp 2 employs a custom-designed solution that detects DC voltage at significantly lower levels without interrupting normal audio playback. This involved extensive testing and refinement, as initial prototypes proved overly sensitive. The final circuit utilizes a precision rectifier built with a zero-drift operational amplifier, ensuring reliable protection and seamless operation.

Taking a tech dive here, let’s talk about JDS’s Octo-Buffers design. The original Atom Amp+ relied on a single LME49600 buffer per channel. While effective, this approach limited power output. JDS Labs explored paralleling multiple buffers to achieve a proportional power increase. However, space constraints necessitated a more compact solution. The answer came in the form of replacing the single, large buffer with numerous, smaller, lower-power buffers. This configuration delivers the desired power increase while maintaining a space-efficient design. An additional benefit of this approach is the reduction of common-mode noise, further lowering the overall noise floor.

JDS Labs evaluated several variations of paralleled output buffers during development. The initial design incorporated four OPA1692 op-amps per channel due to their low quiescent current, resulting in cooler operation. However, this configuration yielded lower power output compared to the Atom Amp+. Doubling the number of buffers to eight was considered to address this issue. However, due to a stock shortage of OPA1692s during the prototyping phase, OPA1656s were substituted. Interestingly, this change proved advantageous, as OPA1656s deliver 75% more power than OPA1692s.

The Atom Amp 2 boasts exceptional THD performance and remarkable power output. Even at maximum volume with 32Ω headphones, the amp delivers pristine audio at 9.22VRMS (26Vpp) for a total of 2.65W of power. With power delivery now limited by voltage swing, JDS Labs acknowledges that a significant increase in power output within a solid-state design would necessitate a transition to a differential output topology. However, such designs introduce their own trade-offs, including increased noise and higher THD. 

I enjoy reading up on manufacturers’ engineering notes very much; they provide priceless insight into the story behind the product. It is fascinating how they maximized the efficiencies of their platform to get these remarkable results. For those who also enjoy reading these, I definitely recommend checking out JDS’ blog.

AMP Performance

Three words sum up the nature of the Atom Amp 2: transparent, clean and powerful. This amp offers incredible value for money. With 2.6 watts of power, exemplary measurements, a compact footprint, and an affordable price, it truly leaves nothing to be desired.

Like the Atom+, the Atom Amp 2 delivers a neutral, linear, and transparent sonic signature. JDS Labs has once again refined an already outstanding product. Doubling the power of the original whilst improving the same resolving, revealing, and pristine SQ is a remarkable feat. The Atom Amp 2 faithfully reproduces your source and tracks without coloration, with a quiet background and extremely low levels of distortion, even near max volume. At $129 USD, this amplifier is an undeniable bargain. JDS Labs are to be applauded for defying the industry-wide trend of price markups and demonstrating a truly customer-centric approach, especially given that this product is manufactured on US soil.

Just like the Atom+, the Amp 2 does not feel particularly bright or warm; it is linear, and it reflects the source as-is. If I pair it with K9 Pro ESS, I get a neutral-warm signature with my VE7s. If I switch to the K9 AKM, I hear a slightly less detailed but more musical, slightly more articulate, and slightly warmer reproduction. The amp is useful for evaluating DACs due to its as-is approach and linear response. It makes it easy to distinguish the signature differences between the implementations. There’s really not much to tell you about it; it’s an amplifier and does a wonderful job of amplifying. I honestly think that every audiophile should have a no-frills Atom 2 Amp on their desk. It’s simply that good.

The review continues on Page Three, after the click HERE or by using the jump below.

Page 1: JDS Labs, Atom DAC 2, What’s New?, Packaging & Accessories, Design & Build Quality, Features, DAC Performance

Page 3: JDS Labs Atom 2 DAC & AMP Stack Performance, Pairings & Comparison, Last Words