Atom Amp+: Closer Examination

The JDS Labs Atom Amp was what started the super popular Atom line, and since the release of the Atom Amp+ in July 2021, there has been the release of the Atom DAC and DAC+ we just saw. This is a testament to the longevity of the Atom Amp, which has been recognized as a good value amplifier. However, there's been competition coming from the likes of Schiit and Topping, so perhaps it was good that the output delivery refinements made when building the Atom DAC+ were substantial enough to both fit into the Atom and make for the new Amp+. Aesthetics are on point with the Atom DAC+, down to the use of the same style, form factor, and material composition.

The front now reads Atom Amp+, of course, and has a 1/4" (6.35 mm) stereo output for headphones. A gain button switches between low gain, which is better-suited for IEMs and low impedance/high sensitivity headphones, and high gain, which is going to match the 2 Vrms output from the Atom DAC+ for more power. The Atom Amp+ supports dual inputs too, and here too is a switch for easily swapping between the two, though these two switches are not marked as clearly as I'd like, especially for the DAC+. In the middle, again taking up the same spot as on the DAC+, is a volume control wheel that also has an LED ring beneath. There is a $5 knurled replacement aluminium knob for those who prefer it.


The Atom Amp+ is an amplifier first and foremost, but it is also a preamp for those wanting to use the volume control, and DAC output if used as a stack, with powered speakers. This is why there is a set of RCA outs on the back too, making this all the more conducive for desktop usage with a set of desktop speakers. Preamp mode is best paired with the amp in low gain for obvious reasons. Plugging in headphones cuts the preamp out to where the volume control and gain work on the 1/4" output itself. Next to the RCA out on the back are the RCA inputs typically connected to a DAC, such as the Atom DAC+ we will be using. There is an optional 3.5 mm input too, which is where that input toggle on the front enters the picture. As with the Atom DAC+, we see the certification logos next, and the power input at the end. The back is identical to the Atom DAC+, including for the four rubber pads, of which the front two are again raised slightly.


Seen above is a closer look at the four Philips screws under those rubber pads holding the Atom Amp+ together, removal of which once again has the top lid come off for a closer look at the meat of the PCB. As indicated, we see a lot in common with the Atom DAC+, including the analog circuitry. Harder to photograph than the hand-matched custom potentiometers were the NJR NJM5532 dual-mode low noise op-amps, which comprise the primary power upgrade in the Atom Amp+ over the previous-generation Atom Amp that used the NJR NJM2068 on the input stage. Between these two main changes, and any associated smaller circuitry ones, the Atom Amp+ boasts an SINAD of 119 dB, up from 113 dB on the Atom Amp. Noise has decreased ever so slightly too, although there is a bigger improvement in crosstalk (rated at 10 kHz) from -86 dB to -92 dB. What is more important, and remains unchanged, is the low output impedance of 0.1 Ω, making this suitable for just about anything plugged into it, certainly everything I have at my disposal here.