Audiophilepure

https://pt.audio/2025/06/08/atma-sphere-gem-integrated-headphone-amplifier-review/

What I have here is a really tiny amplifier. Actually, it’s way more than that; this gem really does duty as an integrated amplifier that can handle both efficient speakers and a bevy of headphones, ranging from the efficient to the not-so efficient. I’m not really much of a headphone guy, so I employed this Gem as an amplifier for my really efficient Charney Audio Maestro-X single-driver speakers.

A bit of history about Atma-Sphere first. Ralph is best known in the industry for pioneering two things: output transformer-less (OTL) vacuum tube amps and use of fully balanced circuitry and connections in his amp and preamp products, and these design elements are highlighted in his mainline designs to this day. Interestingly, the Gem (on the surface… see below) sports neither. Right on top are exposed output transformers, and a quick look at the rear panel indicates the presence of (only) single-ended RCA input jacks. Was Mr. Karsten perhaps being a bit contrarian here with this design?

The following sound impressions were made after 100 hours of burn-in for the stock tubes. I used the FiiO JM21 and HiBy R4 as DAPs, the Oppo BDP-83 as a CD transport, my MacBook Pro as an alternative, and the Soundcraft Absolute 4P powered speakers for XLR-balanced out.

Listening devices included the SJY Horizon, Kennerton Rognir, AKG 240DF headphones, Campfire Audio Supermoon, Solaris 2020, and Drop x Campfire Audio Dark Star IEMs. The 4Ps were used for balanced output, and my McIntosh MA6100 as a power amplifier (aux-in), and pre-amp in.

One of the most important updates with Element IV is full integration with JDS Labs Core™, their new web-based control platform. There’s no desktop software to install, no bloat or anything. You connect the device via USB, open a supported browser (Chrome, Edge, or Firefox), and voilà.

You now have access to the fully customizable 12-band EQ and the rest of the device settings. PMEQ’s each band is fully adjustable in frequency, gain, and Q factor, with all changes saved directly to the device’s hardware. The UI is responsive and easy to use. Once EQ is set, it persists across reboots, input changes, and even when switching from USB to optical.

Like many more affordable options, the TA-84 doesn’t have a power button on the front, and you have to reach behind it to power it on and off. Take care not to accidentally press your hand on the hot tubes that can reach over +70C. They won’t immediately burn you like hotter-running large power tubes, but you can hurt yourself by pulling your hand back instinctively.

The back also houses switches for gain toggling and switching between the DAC and AUX RCA inputs. DROP specifies the gain of the TA-84 as 16dB, but my own measurements show that the voltage gain is around +18dB on low and +20dB on high gain. With a Sennheiser HD6XX, this meant that I was around midnight on the volume control for most of my listening.

https://pt.audio/2025/05/04/lta-velo-headphone-amplifier-review/#google_vignette

While there is no dearth of choices in the $2-3,000 price point, equivalents to the $2,100 Velo are rather scarce. There’s plenty of solid state choices, but just a few more standard OTL tube amps and only a handful of the most affordable transformer-coupled designs. In general, a pure OTL design will tend to sound a bit thinner and more upper-midrange focused than the ZOTL technology from LTA, whereas a transformer-coupled amplifier will often be thicker, and darker. This leaves us in the company of quite clean sounding tube amps which generally cost more or hybrid or solid state amps that sound particularly smooth. 

All of this is to say that I think the LTA Velo stacks up quite nicely at its price point. Given the design considerations and how much good sound is on offer, the Velo to my ears and eyes is a welcome exception to the “products must always get more expensive” mantra. While you won’t necessarily be pairing the absolute hungriest planar magnetic headphones with it, it pairs very well with most dynamic and planar headphones, from Audeze to Focal, and plays all of them with that signature LTA balance of good tone, pleasantly warm-of-neutral frequency balance and dense harmonic structure. Definitely worth a listen if you’re in the market for a tube headamp in this price range.