Companion One

MSRP $595 $199 (USD, EUR)

Portable USB DAC (PCM384, DSD128) & Headphone Amp • WiFi Audio Streaming 24-Bit/192kHz • Supports Windows, Mac, Android (*OTG) and iOS devices
(Companion One has been discontinued. Companion 2 is under development that includes a free player app to decode high resolutoin music files).

The Celsus Companion One, an advanced and comprehensive portable High-Res audio companion, features a high-performance headphone amp with better than 115dB signal-noise ratio. The USB DAC, utilizing ESS’s class-leading ES9018K2M DAC, decodes up to DSD128 and 384 kHz PCM audio formats. A built-in Wi Fi network allows Companion One to be used as a media streamer capable of PCM 24bit/192kHz streaming. A digital Toslink S/PDIF and one 3.5mm analog output connect Companion One to a wide array of devices.



Unique Market Position

The Celsus Companion One is the world’s first high-performance DAC that supports both USB cable and wireless connections to Windows, Mac, Android (*OTG) and iOS devices. Another world’s first is the Companion One’s ability to decode and stream 24bit/192kHz music files. Thus the user enjoys the highest quality desktop USB audio playback available and, with the push of a button, streams music from connected devices with better than CD-level resolution.


Low Distortion and Jitter

With asynchronous USB audio clocking via two internal high-accuracy low-jitter clocks for 44.1kHz (88.2/176.4/352.8) and 48kHz (96/192/384) sampling, the Celsus Companion One optimizes USB digital data transmission for ultra-low-jitter performance with better than 115dB signal-noise ratio.


Powerful Headphone Amp

The Companion employs an OPA1612 for I/V conversion and an AD8397 for voltage gain and current buffering sufficient for driving the marketplace's most problematical headphones.


Build and Sound Quality

The Celsus Companion One’s curved frame, machined from a single block of aluminum, is a pleasure to hold. With its top and bottom gorilla-glass covers, the Companion One’s build quality surpasses that of any portable DAC on the market today. The unit’s signal path and headphone amplifier circuit have been painstakingly optimized for maximal headphone performance.  Discerning audiophiles are bound to appreciate the Companion One’s dynamic and richly detailed music presentation. 



USB Audio:

  • Supports PCM and DSD audio formats
  • PCM audio: 16/24/32-bit audio data, 44.1/48/88.2/96/176.4/192/352.8/384 kHz native sample rate.
  • DSD audio: DSD64 and DSD128 native decode.
  • Asynchronous USB audio clocking with two internal low-jitter clocks separately for 44.1kHz (88.2/176.4/352.8) and 48kHz (96/192/384) sampling.
  • Switches between USB High Speed (480Mbps) and Full Speed (12Mbps)
  • Extremely low latency
  • Supports ASIO
  • Supports Windows, Mac, Android (*OTG) and iOS devices
  • * Most Android 4.x devices do not directly support USB Audio. Users have to use "USB Audio Player PRO" app on Google Play store to play hi-res music through USB OTG output. USB Audio is supported on Android 5.0 and later version.


Wi-Fi Streaming:

  • Supports PCM format: 16/24-bit, 44.1 / 48 / 88.2 / 96 / 176.4 / 192KHz
  • Supports uPNP network media streaming and Airplay
  • * We recommend BubbleUpnP UpnP DLNA Player for Android devices.



  • Digital: Toslink S/PDIF
  • Analog: 3.5mm
  • Volume Control: 100 steps
  • Gain Control: 2 levels, for earphone impedance of 16 to 300 Ohm


Included Accessories:

  • Genuine leather carrying case
  • Micro USB to Apple Lightning cable
  • Micro USB to Apple 30-pin cable
  • Micro USB to PC USB cable
  • Micro USB to Android OTG USB cable
  • Protective film cover and microfiber cloth



  • THD+N:0.001%at 0dB, 10 kOhm load
  • Frequency Response:20Hz – 22kHz (+0, - 0.5dB)
  • Output voltage (0dB):High Gain 3Vrms; Low Gain 1.5Vrms
  • S/N ratio:> 115dB (at 2Vrms)
  • Crosstalk:< -110dB
  • Dynamic range:> 115dB
  • Output power:160mW @ 32 Ohm, 28mW @ 300 Ohm
  • Weight:0.6lb

Companion One Reviews


Sound & Vision's Top Picks

"…I auditioned the Companion One with a pretty wide range of headphones, including the Sennheiser HD-650 (later version), Ultimate Ears UE-10 IEMs, HiFiMAN RE-600S, and the fairly tough load of the HiFiMAN HE-5s. Even with the HE-5s I never felt that the Companion One was about to run out of steam, and the sound remained clear and dynamic. So despite looking a bit limited on paper, in practice the amp could drive real world loads to satisfying volume with ease…

…What immediately struck me was how the basically neutral tonality of the Companion One allowed the true character of the recording and connected headphones to shine through…With record after record, and through all kinds of headphones I soon came to the conclusion that the Companion One was really more like a tool that allowed me to audition recordings and headphones, than a device with a sound of its own. It always remained neutral and simply let me hear the best of whatever it was connected to…", Michael Trei, Sound & Vision


read more


"...It is the only one right now I can think of that is capable of doing so much and as such the value for money in todays 'do it all' fussy media market is actually rather good at $595. The fact you can run it out of a Mac, PC, iOS or Android wired is already a big advantage but to throw in wireless at a high resolution capability is a definite edge for now... The direct wireless mode sounds superior to any aptX or Kleer device that I have heard to date and is half the price of the admittedly awesome Flow...", - MARCUSD,

 read more


"…the Companion One feels less like a portable audio product and more like an extra-thick iPhone (or some other ergonomically-pleasing Apple-built device). What’s difficult to convey in words is the polished and refined look and feel of the Companion One (it really is so well designed that it seems as if it’s missing an Apple logo), not to mention the reassuring heft of the unit in hand, which provides a constant tactile reminder that this is a serious piece of kit and not…",- Chris Martens, Editor-in-Chief/HiFi Plus

 read more


"... Companion One is a damn good portable amp belying it’s modest price. It doesn’t have any point in the music that glaringly stands out. Music through this unit has a nice flow to it and the amp stays out of it’s own way. It works with a wide variety of headphones and, even though it’s touted s a portable unit, it shouldn’t be limited to IEMs, buds or portable cans. I primarily listened with the AKG Q701 along with time with the Hifiman HE560. plugged into the Celsus. Neither of which are exactly easy to amp...", - Ross Feinberg, Senior editor/HEADPHONE.GURU

read more


"...Companion one is not just a WiFi amp. My primary intention was WiFi capability rather than USB function. I first thought the USB function is an extra but actually it is not just an extra to the WiFi capability. Companion one is damn good as an USB DAC/amp. Sounded nice as a companion of Smartphone plus the accessories are great to start-up Smartphone audio setups whichever you are using iPhone or Androids...

...Speaking of sound quality, I have to confess I had not take much care about sound quality. I thought this is the first WiFi amp I had been waiting for, so my focus was only on WiFi usability. But to my good surprise, Companion one sounded remarkably nice. Even if I forget the WiFi capability, Companion one could be one of the best sounding portable DAC/amp to date...", Sasaki, contributor/


"…One micro USB is for power and one is for audio. One output is for headphones and there is an S/PDIF out and a line out. There’s also a cable to connect my iPhone direct and apparently it’s wireless too. It’s designed to do quite a bit in one solid, well-designed little package. It’s also battery powered, so not only can I take it with me, I can use it while moving from place to place…I plug the desktop computer into the Companion One and the Audeze headphones into the other end and turn it on. I wasn’t really prepared for what I heard - the sound was amazing and I was instantly impressed…", Rick Hopkins, founder/Sonic Unity


"...Companion One plays exactly as you expect from a high performance device. The Sabre 9018K2M - good detail, fast speed delivers fine nuances...the only real noise is heard during the pauses between tracks, listening to music and it does not interfere...the wireless functionality is pretty new and unprecedented, and only very high-end home audio units have thus far provided high-resolution wi-fi streaming…The Companion One is a sure sign of things to come in the future...", - PAVEL DMITRIEV, editor/


"…When you want to stream on a serious level, the Companion One is one -if not the best portable USB/DAC/AMP at the moment. It is, taking in account the Wifi and Line out possibilities, a unique product. The Companion can be, using the line-output, applied as a DA converter for a hifi system. The Companion One, is, as far as I'm concerned, a companion here to stay and capable to interest people for quality in music…", Ernst Neve, editor/Hifi Video Test (Netherlands)