In the world of high quality music reproduction and audiophile equipment, computer based systems are still in it’s infancy relatively speaking. Turntables  get their roots from the original 1877 Thomas Edison invention the phonograph. Turntables ruled the word of music for well over a century and have since had a resurgence of popularity after almost fading into oblivion less than a decade ago. Let’s not forget the short-lived 8 track. Cassette tapes had a several decade life due to the promise of portability and the ability to record your own music and playlists. Compact discs were supposed to save the world and cure hunger. The reality fell short of those expectations. Especially in the early years of digital music reproduction. However, through the years, the CD’s sound quality as a music media did improve quite a bit.

Apple’s iPod and the mp3 set out to retire the need to have a 100’s or 1000’s of discs to lug around with you with a promise (there’s that word again) of portability. In that aspect they were successful. What happened in the process the mp3 industry destroyed the sound quality of recorded music by compressing the size of music files in order to save storage space. Admittedly hard drive space wasn’t as cost effective as it is today. There was a backlash throughout the audiophile community from listeners that were used to or demanded a higher level of sound. Particularly among the expanding headphone enthusiasts who are appreciating the explosion of headphones that, in many cases today, sound better than expensive speakers.  If computers and digital audio were to become accepted with those that only demand the best sound the products needed to be able to produce higher quality fidelity.

A few years ago, along with less compressed and lossless music file formats, external DACs and  amplifiers dedicated to personal portable music systems and computer-based audio began to emerge. The initial attempts by some manufacturers were little more than a DAC with a UBS port added to them without addressing the pitfalls of extracting that signal coming from the computer and being fed through their components. Jitter(unwanted noise) being one of the culprits. Also, in the beginning, the makers of audio gear didn’t expect or anticipate that listeners would not only plug in a headphone designed for portable use but would want to enjoy their expensive statement headphones on a computer-based or personal audio system.

During the past decade the technology has ventured forth and with each passing product generation not only have the makers of DACs and headphone amps seen the light and sound quality has leaped forward, they’ve integrated the two seamlessly into single systems.

In walks the Companion One by Celsus Sound


On the surface the Celsus Sound company may seem to be just another new endeavor established to cash in on the growing personal audio phenomenon. When, in fact, it is backed by prior wonder-geek  formerly of Nuforce; Jason Lim. I happen to have the uDAC and it is one of the DAC/amps I use as a baseline. Having that lineage is a good foundation for Celsus Sound to build upon.

The $599 Companion One (CO), according to their own website is “an advanced and comprehensive portable High-Res audio companion”. To me it is a portable rechargeable DAC and amplifier combination that is USB and Wi Fi usable; able to stream the latest in 128 and 384 kHz audio formats as well as standard PCM formats. What this means is you can use the Companion One to wireless listen to your current Windows, MAC,  Android or iOS device. One can also go the more traditional route and have your music go through the DAC/amp via USB. Crunching all of those 0s and 1s into useful analog music is the ESS ES9018K2M DAC. A digital Toslink S/PDIF and an analog 3.5mm connect the Celsus to your chosen music device

Upon first glance the CO looks like the iPhone 6. Right down to the Gorilla Glass  adorned on the front and back. Yet it’s not. The Companion One is about twice as thick and has a good deal more heft to it. The unit feels as if it’s been milled from a single piece of metal when, in actuality, it has been from aluminum. It has that quality feel of metal and glass that plastics just cant duplicate. Because of it’s size and heft I’d call it more part of a portable travel kit than one of an active gear accessory you’re likely to carry around with you during a hectic day.

Aesthetically it’s quite austere. Initially, since it does resemble your favorite smartphone device, I expected it to have tons of wiz-bang doodads and a flashy graphics display. There’s a lot of real estate on the front blackened out glass that seems to beg for the latest HD programming to be displayed. None of that happens, however, what you do get is a small LED on the top that acts as a power and mode indicator in a funky wave pattern. On the bottom there are four tiny blue LED lights to display the battery life. Hey it’s portable, it has to have a rechargeable battery!  In the center of the glass is a slightly lightened watermark with the company logo. In the end, that’s all the Companion One needs. Even if you might want it to display the latest Mythbusters episode.

There were a couple of issues I did have while setting  everything up. While the written directions aren’t obvious, you do have to download a driver program off the Celsus website to get the Amp/DAC to work with iTunes. Also, even with calls to the company, I never could configure the wifi to work together with my computer. Perhaps it was because I use Windows XP I’m not sure? I used the amp connected via USB and it worked with few issues during the test period.

  • laptop WinXP
  • iTunes
  • music ripped from CDs into .wav or Apple lossless formats
  • AKG Q701
  • Celsus Sound Gramo One
  • HiFiman HE 560
  • Shure 940
  • Musical Fidelity MF100
  • Beyerdynamic T51p
During the review period I used the Celsus Sound Companion One as my only constant. As it’s been a while since I’ve listened to a wide variety of amplifiers and DACs, I’m going to let the Companion One stand on it’s own merit. It would be unfair to compare or contrast other amps that I’d have to recall from memory. If I can’t listen to two pieces of equipment side-by-side, I won’t use it as a barometer.  Owning  the Nuforce uDAC the Companion One is a better kit and at 5X the price it should be superior.  As nice is the Companion One’s distant cousin (the Nuforce) doesn’t compare fairly

I have used several headphones during the time I’ve spent with this portable DAC/amp. The one that I’ve spent the most time with is the Q701. Partially because I happen to like the headphone, partially because I’m quite familiar with it’s tonal characteristics and because I believe the AKG happens to be priced on the Celsus’ level. The CO performed almost equally across the board with whatever headphone was being used.

Between some personal obligations I’ve had and my love for motorcycles I’d taken a short hiatus from audio gear and headphones. I was in a specific situation where I needed to have ambient situational awareness at all times and was incapable of using headphones for even short periods of time. Fortunately I now have to opportunity to listen to head gear and music. Please bare with me if my terminology isn’t perfect. I will do my best to describe to you what I am hearing  and what Celsus’ Companion One sounds like to me. Enjoy the following…

Noise Floor

I’ve always felt that the predominant foundation of an amp’s quality was how quiet it is. A high or low noise floor sets the stage for a good deal of an amp’s personality. A totally black backdrop seems to make the music flow effortlessly into space. Micro details pop out and additional textures can be heard. Also, a quieter amp seems more powerful allowing the music to not have to muscle it’s way to the top of a musical listening experience.

Although I didn’t find the Celsus to be as quiet as other separate solid state amps with large, meaty power supplies, it does more than a credible job at keeping noise at bay. During quiet passages there is a slightly elevated floor that falls a little short of a stark black backdrop. That said, unless your are listening in a critical manner, it’s not an issue.


If dynamics and dynamic range is defined by the differences or perceived differences between the quietest passages and the loudest passages within a song or music then we’re on the same wavelength. If you’re using a different definition then I don’t know what to tell you. I take a great deal of time going over dynamics with any equipment I evaluate because if the dynamic range of a particular amp is tight it has a way of sounding muffled and one dimensional. If the range is nice and wide it adds to the dimensionality and overall clarity of an amp or piece of equipment. Don’t, however, mistake dynamic range with soundstage or overall clarity. The DR can only highlight those qualities and not define them.

I find the Companion One to be a relatively dynamic amp. Especially for a portable product and one at a modest price point. It certainly expands the louder and soft passages beyond anything your iPhone, iPod or smartphone device can attempt. Tchaikovsky’s “1812 Overture” is probably the quintessential piece to measure dynamic range. You get a good sense of the disparity between quiet passages and more explosive ones. I find the CO handled this difficult music without strain when using the AKG Q701. Unfortunately I didn’t get to try it with the Hifiman HE560 planar while listening to 1812, however, all the other headphones had no struggles. Even at high volumes.

Soundstage and Imaging

In my experience it usually takes quite a bit of power to have an expansive soundstage with solid state amplifiers. Under-powered portable amps usually collapse the staging to either keep the music within one’s head or not expanding much beyond it. Although the Companion One doesn’t let you forget you’re, in fact, wearing headphones, it does a darn good job of enlarging the scope of the music. When listening to Pink Floyd’s “On the Run” off of the 2011 remaster of DSotM you can get a sense of the footsteps’ distances coming and going.  “The Afternoon: Forever Afternoon (Tuesday?): Time to Get Away” [Tuesday Afternoon] from the Moody Blues’ Days of Future Passed has an ethereal quality that the Celsus is able to finely capture.

Because the CO is able to convey larger than expected staging, the imaging is also surprisingly good.  The instruments suggest a proper placement within their scope. The Celsus never sounds congested.


This DAC/Amp reveals surprisingly satisfying details. It’s not hyper-resolving that would make the Celsus etched. It just goes about it’s business letting the music expose what’s recorded.


I tend to like fully extended high frequencies over gear that might have  a tendency to roll off the highs to give it a warmer sound. The Companion One extends all the way up the frequency scale without any brassy or tinny sound that many lesser amps might have. Especially portable music players like a smartphone might inflict .My two favorite songs to test how natural the treble will be reproduced is Boston’s Foreplay/Longtime off their  eponymous album and the glass tinkles during the intro of Pink Floyd’s Wish You Were Here from the album of the same name,  The Clelsus shines during these passages and makes the upper frequencies a pleasure to listen to with little evidence of piercing.


Most of the music we listen to lives right here within the center of the frequency scale. The Celsus Companion One doesn’t stand out… And that’s a good thing. I’m not really the biggest fan of mid-centric equipment of any type. To my ears it seems to make the music sound synthetic and can tend to congest the sound. This Celsus does none of those. There’s an even hand that this amp deals. This means that from the top of the midrange to the lower portions it all flows naturally.


It’s my belief that bass (or the level of bass) is a hot topic. More so than, say, the midrange. There re those that like bass-heavy music and equipment that accentuates that. Then there are those, such as myself, that prefers a much more balanced approach. A flat bass that extends low and has solid impact and plenty of detail is what this CO does admirably. Listening to “One of These Days”  From Pink Floyd’s Meddle, the amp delineates the dueling bassline  easily. Pucifer’s “DoZo (Version 2)” has strong depth during it’s bass-heavy song.


I am fond of the texture the Companion One can draw out of singing. You can hear the timbral and vibrato changes in a singer’s voice. This adds more realism that not all amp/DACs can accomplish. One of my favorite female vocals comes from Janis Joplin’s heart-felt song “A Woman Left Lonely“. It’s one that could possibly make you understand why she is so beloved. Play it with the Celsus and you’ll be swept away.


The Celsus 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. Particularly thr HE560 which can be a bit demanding compared to a more typical portable headset.I do wish it had more features and were a bit easier to use. Those are minor quibbles for an amp/DAC you can travel with and have a high quality music experience. Overall I am pleased with the Companion One. It’s a piece of gear that combines everything someone could need. Is the Companion One from Celsus Sound truly a companion for everyone? I don’t see why it shouldn’t be. It gets my recommendation.

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Ross Feinberg

  • RockStar2005
  • 2015-07-27 03:04:00
  • Great and very detailed review Ross! You really covered every single aspect of the CO quite well. I just ordered the CO a couple of days ago and CAN'T WAIT to try it out!
  • Reply

  • Peter
  • 2015-03-25 21:22:04
  • Awesome write up Ross! Really enjoyed the read and this looks like a great portable option!
  • Reply

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