<i>Cloud Nine Portable Amplifier</i>
<i>Cloud Nine Portable Amplifier</i>

Cloud Nine Portable Amplifier

Estimated processing time for new orders
1-3 days
Last updated on Jul 19

Cloud Nine Features

Reference Grade

Cloud Nine is an 18V (2x 9V) battery-powered portable amplifier capable of driving not only sensitive in-ear monitors, but will drive even the most power hungry, high impedance headphones - which also means all the IEMs and headphones we build custom cables for will work with this amplifier.


With a precision amplifier followed with dual mono operational amplifier integrated circuits in the output stage, Cloud Nine will provide superior sound quality, excellent channel separation for improved imaging and clarity, unity gain stability, rail-to-rail output, while maintaining ultra low noise and distortion numbers.

9V Powered

All 9 volt batteries (Alkanine, NiMH, Lithium) will work with this amplifier and can run from 20 hours to 80 hours. Expect long battery life. [Based on battery type, mAh, gain, volume levels]

Gain Switch

Multi gain switch is added for the best performance (Low for IEMs, Mid for headphones, and High for high impedance headphones)

Battery Switching

Amplifier features back panel with thumbscrews for easy battery switching that should take no more than one minute.

Safety Feature

If you happen to put one or both batteries the wrong way, Cloud Nine has an added reverse battery protection feature to prevent any damage to your batteries and amplifier.

Portable Sized

The power of a full-size desktop amplifier in the size of a small portable amplifier, measuring at approximately 2.3" x 4.5" x 0.95".

Aluminum Enclosure

Thick anodized aluminum protects components while keeping it lightweight.

High Quality Components

Only the highest quality components are used, including military grade printed circuit board, Panasonic capacitors, Vishay/Dale precision resistors, and Texas Instruments ICs.

Cryo Treated

The entire amplifier goes through cryogenic treatment to improve durability and sound quality.

One Year Warranty

All amplifiers come with a one year warranty. Should you experience an issue, contact us so we can resolve it as fast as possible in order for you to get back to listening.

Made in USA

Cloud Nine amplifiers are assembled in Los Angeles, California, USA.

Technical Specifications

Device Type: Solid State
Battery Type: 9V (x2)
Frequency response: 20hz - 20khz +/-0.1dB
Gain: 1x/0dB, 5x/10dB, 10x/20dB
Input impedance: 50K
Output impedance: <1 ohm
Maximum output: 200mA
Power rating: 1.28W into 32 ohm, 1W into 50 ohm, 250mW into 300 ohm, 120mW into 600 ohm
Noise floor: ~-150dB
Protection: Reverse battery
Input/Output: 3.5mm Switchcraft / 3.5mm Switchcraft
Dimensions: 2.3" x 4.5" x 0.95"
Weight: 3.2 oz (without batteries)


"The sound of [Cloud Nine and HM-700] is simply amazing, very detailed and everything is balanced, I actually love this setup even more than my desktop setup at the moment..." - Shiorisekine, Head-fi.org

As for performance-by-numbers, Cloud Nine is impressive on almost all fronts… it provides plenty of current into low impedance loads to keep distortion to a minimum while managing pristine frequency responses. It is an excellent earphone amplifier.” - Nathan, Headfonia

“Overall, we’d use the words like “crunchy” or “chewy” with only a little softening of the most extreme tracks, and tons of headroom and space around vocals. Instrumentals feel fast and precise, vocals and bass have a bit of an old-school vibe, with crisp and crystal clean harmonics and percussion. Tons of detail ensure you hear everything, and it’s fairly neutral, flat-response.” - Greg,

“The Cloud Nine doesn’t sound like any of my other portable amps and I’ve had the opportunity to listen to a lot of different amps. It’s also one of the few amps that does everything from IEMs to Orthodynamics without any effort. Switch the gain, set the volume and enjoy the music. That’s how it works.” - Lieven,

“… Cloud Nine is a very liquid smooth flowing amplifier with a big soundstage… [Starting] at $349.99, the plusSound Cloud Nine really does more than what could be expected… - Cholo Isungga, WhenInManila

“Overall then, the plusSound Cloud nine represents a powerful portable amp that can be used to drive virtually any IEM and the majority of headphones to sufficient auditory levels. Not many portable amps can boast that and is one of the reasons the Cloud nine is a popular tool for on the go. I am particularly impressed with its ability to convey a musical tonality that is devoid of any harsh or sharp leading edges. In addition, the expansive properties of the Cloud Nine make it a force to be reckoned with in the arena of mid to hi-fi amps” - Smit Patel,


Headfonia Best of 2015 - Portable Amplifier category
Headfonics Top Gear of 2015 - Portable Amp



"This amp sounds really good!"

"Very impressed. It can drive the LCD-2s with ease."
"So far, so impressed. Very well done noise signature and great way of getting into and out of the amp."
"With Cloud Nine, the PR opens up and becomes extremely detailed and revealing."
"Wow! This was exactly what I was looking! Portable. Lot of power. and incredible sound! Amazing product!"
"Very happy with the amp. They can drive my HD800s at only mid gain!"
"Cloud Nine is great. It has the best volume control I have ever experienced on a portable... "
"I have purchased some of your cables in the past, but the Cloud Nine amp is by far my favorite product!!!"
"Everything sounds cleaner, detailed, and balanced. Thanks again for producing such a great product and your exceptional service."
“One word: Amazing!!! It is a significant improvement over other portable amps I own.”
“Top notch sound quality and build. Very impressed, thank you again for the great service.”
“Amaaazing control and power for earphones and most headphones. Stupendous sound.”