JDS Labs Atom Amp+ Hevi Review

UI & Usage

Everyday Use

Tiny but mighty, the Atom Amp+ Hevi is a breeze to use. All you have to do is plug the power plug, connect your DAC through one of the two line inputs, and turn the volume up to initiate the amp.

Obviously, the best pairing would be with the Atom+ DAC, to create the perfect little stack, but you could virtually pair the Atom Amp+ with every source you own – as long as a line output remains available. I paired that amp with my Hifiman EF400 and the FiiO M17, and I didn’t notice any issue during my test : just plug your headphone, and you’re good.

Where things get interesting though, if when you DON’T plug your headphone in. Like The Element, the Amp comes with a kill switch, muting the headphones out to route all the signals into the RCA output. A simple trick that allows you to listen to your active speakers, or classic amp, when you don’t wear your headphone, and immediately switch to your headphone whenever you plug it.

Apart for that, there’s not much to be said, it’s pure plug&play delight.

Noise and power

Noise: nothing to say here, it’s dead silent, and the 1.0x gain setting is perfectly suited for anything but ultra-demanding headphones. And if the higher the gain, the higher the noise I couldn’t discern any noise here, even with the volume turned on to the max and no music playing. EMI shielding did a great job and I never encountered any parasites or any real buzz during my listening.

Power: The Atom Amp+ Hevi delivers an astounding level of power. Enough to drive even the most demanding headphones, making it a versatile and reliable choice for any audiophile. With just 1W of power available, the amp maintains its exceptional sound quality across a wide range of headphones and IEMs and even tackles SMSL in that regard – even though the HO200 pushes higher, but no the HO100.

Specifications

For the nitpickers and nerdy ones here, I’m giving the specs and technical sheets. For all the others, you can just go to the next page to see how the Atom Amp+ Hevi performs.

Ultra (Hevi) High Power

Yagiz already wrote a lot about the Atom Amp+ enhancements, so I’ll just quote him here:

When we examine the detailed post shared by JDS, we see that JDS has improved the performance of the amp by making minor changes on the amp. They upgraded the input stage ICs from NJM2068 to NJM5532 and did small adjustments to supporting resistors.

They state that they were not satisfied with the 2019 ALPS potentiometers used in the previous Atom Amp, so they switched to custom-made potentiometers which were produced specifically for the Atom Amp+. All the custom-made potentiometers are hand-matched for tighter L/R balance to levels ~20dB lower than the Alps was able to offer. And best of all, none of these upgrades were reflected in the price.

Power wise, the Atom Amp+ can sustain up to a 600 Ohms load, and maintain a solid 9.05VRMS continuously. A very good number taking account of the size of the amp, even more if you think about the price. SNR exceed 122dB, noise is minimal at juste 1.99 microV across the full frequency range and channel imbalance should not exceed 0.6dB – each and every volume knobs are precisely hand-tunes by the team. Marvelous!

Finally, I’ll also quote JDS regarding the differences between the regular and Hevi versions:

• The circuit board is the same whether you choose Standard or Hevi construction, so performance is the same either way. We’ve resisted the urge to alter Atom’s electronics[…]
• Atom Amp+ Hevi feels substantially more rigid, with internal standoffs bolting the new aluminum top surface to the circuit board. Its longer aluminum knob also feels more stable while adjusting volume.

So yeah, same electronics, but stiffer case and longer… knob! For $10 more only, what’s not to like?

Full specs

Physical specs

• Model: JDS Labs Atom Amp+
• Type: desktop headphone amplifier
• Outputs: 6.35mm TRS, RCA out
• Inputs: 3.5mm TRS, RCA in
• Supply : 16VAC (separated supply)
• Size : 12.7 x 14.73 x 3.56 cm
• Weight: 480g (without power supply)
• Price: $114

Output power

• Max Continuous Power @ 600Ω136mW (9.05VRMS)
• Max Continuous Power @ 150Ω545 mW (9.04VRMS)
• Max Continuous Power @ 32Ω1 Watt (5.66 VRMS)
• Dual gain : 1.0x / 4.5x
• Output Impedance< 0.7 Ω

Output specs

• Frequency Response, 20Hz-20kHz+/- 0.01dB
• SINAD @ 2VRMS, 1kHz119 dB
• SINAD @ 50mV, 1kHz90 dB
• SNR (20-20kHz)> 122 dB
• IMD SMPTE-95 dB
• Noise (20-20kHz)1.99 μV
• Crosstalk @ 10kHz 150 Ω-92 dB
• Input Impedance10k Ω
• Channel Balance< 0.6 dB

The article continues on Page three, after the click here.

Page 1: about JDS Labs

Page 2: Usage, Bundle, Specification

Page 3: Sound performance