Review: Stoner Acoustics Ruby – The Miniature Amp

Disclaimer:The Stoner Acoustics Ruby was delivered to me free of charge directly from Malaysia.

Stoner Acoustics

I first read about Stoner Acoustics and the UD100 mini DAC a few years ago on Head-fi. A few weeks later I happened to be at a meet in the Netherlands where one of my friends had already received his UD100. After I listened to that UD100, I ordered one right away. A few years later the UD110 and UD120 DACs arrived and now Stoner has launched their Ruby: a portable miniature amplifier. Stoner so far has only released miniature units but they’re also working on two brand new non miniature devices, the EGD and EGA, and they look very promising!

Ruby Ruby Ruby Ruby

Everyone knows what a ruby is and there are lots of songs about Ruby as well, but what is this Ruby? According to Stoner Acoustics the Ruby is “a cube sized miniature high fidelity headphone/IEM amplifier based on the high DNR Sabre9601, armed with a high precision stepped attenuator, linear battery charger and ultra-low noise LDO, simply for the serious audiophiles”.

Ruby’s specs are:

Attenuator : 21 High Precision Logarithmic Steps
Gain : 3dB
Output Impedance : <2.5ohm
Max Output Rating :

Input 1.60Vrms : Continuous Stereo Output 2.20Vrms into 10kohm
Input 1.25Vrms : Continuous Stereo Output 1.75Vrms into 100ohm (30mW/Ch)
Input 1.05Vrms : Continuous Stereo Output 1.45Vrms into 50ohm (40mW/Ch)
Input 0.88Vrms : Continuous Stereo Output 1.20Vrms into 33ohm (40mW/Ch)
Input 0.78Vrms : Continuous Stereo Output 1.00Vrms into 25ohm (40mW/Ch)

Size : 51mm(D) x 32mm(W) x 32mm(H)

Weight : 50g

Battery life : >12 hours at normal listening level
Charge : Standard Micro-USB 5V

Warranty : 1 year (no warranty for accessories)

Package Includes: 1 x Ruby, 1 x Bag, 1 x Micro USB, 1 x mini-jack 3.5mm to 3.5mm  cable.

Price : USD99 / RM330

Ruby’s build quality is pretty good. The aluminum is well finished and it looks like it can take a beating, I’ve been carrying it around in my bag for weeks now and it still looks and works like on day one. Ruby looks simple, Ruby looks cute, Ruby looks impressive. The big/huge knob on the front is the absolute eye catcher of the amp. It’s got a good grip and with its 21 steps it really allows to set the volume right where you want, even with sensitive monitors. Right underneath the plastic knob are the 3.5mm in- and outputs and while they are all very close together I, once they’re plugged in, find them very easy to use. I often complain about the positioning of the in- and outputs on devices x times the size of the Ruby and yet Ruby’s design with the huge volume dial just simply works. It’s very user-friendly, except when using a cheap 6.3 to 3.5mm adapter for the HD650. When doing that the volume knob touches the adapter and turning it isn’t too easy, it also scratches both the adapter and the knob.

On the back of the device you’ll find the on/off switch and the micro USB port for charging the battery (white LED lights up). I actually have not tested battery life as I always kept Ruby plugged in on my desk. Ruby charges pretty quick and that’s a good thing as I keep forgetting to turn it off after I’ve used it. I think it’s because of the on/off switch is located on the back of the device. That or I’m getting old.

Anyway, the Ruby is tiny and very easy to take along with you on a trip. Ruby is smaller than the volume knob of my V281 but Ruby is also very light. That means the mini amp will be moving around your desk as soon as you move the cables connected to the amp. Because of the rectangular shape of the amp it isn’t the typical portable amplifier you can strap on your DAP or phone using those elastic bands. Well you could but it would look weird. Or you could use Velcro, that would be cool.

All kidding aside, the Ruby is incredibly small. Combine it with one of Stoner’s DAC’s and you’ll have an incredibly portable and complete system for on the go for about $150USD in total.


Ruby was used mostly in combination with my Hugo (I know…) or with the Astell&Kern AK120ii DAP which is really beginning to become my daily DAP. Ruby sounds better than you’d expect, Ruby sounds good. Tuning is more to the neutral side with a slightly more forward sound in some parts but with good body in the bass and lower mids. Don’t mistake forward for bright because it isn’t bright at all. It’s got more smoothness than brightness actually and mostly in the mids section.

Detail level is good, sound stage width is ok, it’s basically what you can expect for an amp of this level. Depth is lacking most in the Ruby but if you compare it to similar priced amps it will be up there with the best. Ruby gives you a more compact or concentrated sound. That’s especially noticeable when comparing it to the high end Picollo and RX. It’s also under the level of the E12A Fiio which to me still holds the best price/quality as a pure IEM amp. Micro details like on the higher end gear are missing in the Ruby, but you get a good smooth sound that is easy to like. Ruby seems slightly thinner in upper mids and treble. Speed and tightness are average compared to the Rx in example (and its most noticeable in the lower area).

Sound continues after the click here or below

3.5/5 - (17 votes)

Lieven is living in Europe and he's the leader of the gang. He's running Headfonia as a side project next to his full time day job in Digital Marketing & Consultancy. He's a big fan of tube amps and custom inear monitors and has published hundreds of product reviews over the years.


  • Reply July 14, 2015

    Dreamriser Kit

    Nice review as always. However I wonder how to attach this little box-shape amp with a DAP like DX90 lol

  • Reply July 15, 2015

    George Lai

    This thing is so small Stoner should have made it with a key ring attached. Then it’ll always be with me.

    • Reply July 15, 2015


      Where ever Hugo right? lol.

  • Reply July 15, 2015


    Looks really funny to me somehow 🙂
    How did you connect to the Hugo? RCA to 3.5mm cable? or 3.5 to 3.5 cable out of the headphone out?

  • Reply July 26, 2015


    would this work to amplify an iPhone into the car stereo? also, are they selling it yet? can’t seem to find it.

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