Stoner Acoustics Ruby Review

Headfonics 2015

Cracking name, Larry Miller would be proud, “Yeah but I don’t know anyone called Ruby” – yeah you do now and it is the size of a postage stamp with a knob on the end of it.

Few amps come in this size, perhaps the FiiO E6 or the Creative E1 and the in-line tiny amp/DAC modules from the likes of AudioQuest and their Jitterbug line but this is all analog, all cube and just the cutest thing you laid your eyes on in the audio world today. It is not a toy, it is fully functional and sells for just $99 from Stoner Acoustics who are based in Malaysia.

If memory serves me right the Ruby has been on the market for six months but it is only now yours truly managed to get my hands on one. Their new website does not seem to be pushing it sadly so here is hoping you can still get one because I think it’s actually a good value little amp and a nice alternative to similar digital amps in the same bracket.

If you hang around E1 in Singapore Or Kuala Lumpur then chances are you might be still able to get one as they are the official sellers as of now of all things Stoner Acoustics. This product line is 100% boutique.

What Is It?

The Ruby is a portable amp measuring around 5cm from end to tip of the volume pot and 3cm wide and tall. This is battery powered so you can class this one as portable depending on how you want to use the DAC function either with a laptop or desktop. It most certainly is pocketable and then some given the size.

It is also an analog design packing a SABRE9601 headphone amplifier that delivers up to 122 dB DNR and -117 dB THD+N which should make it very suitable for IEM users out there.

By picking this rather new amp chip, Stoner Acoustics have managed to bypass large capacitor designs, lower the power supply to lengthen the battery time to a very nice 12 hours as well as in theory produce a noise-free experience all in that miniature cube.


It’s solid, black, its a cube form factor and I dare say pretty hard to do some damage to it. It feels very robust. That being said the gain pot is about one third of the overall length and as such you could classify it as a bit big given the main body size where the amp is housed.

Thankfully its reasonably weighted so it neither tips or angles when a USB charging cable is inserted at the back or when you fiddle with the pot. It feels comfortably balanced despite its 50g weight on paper.

It’s got an industrial or traditional build design with screws on the back and front and the name ‘Ruby’ and ‘Amplifier’ plastered on the top in case you don’t who she is and what she does. Designed and assembled in Malaysia is proudly printed on Ruby’s ass.



On the front, apart from the huge gain pot, you also have 2 jack sockets for line in and headphone out. The output impedance is 2.3 ohms which is not too bad actually for a wide range of headphones but it lags behind more expensive portable amps such as the new RX from ALO Audio which is rated at 0.5 ohms and highly sensitive to boot.

Even the cheaper amps such as the FiiO E06k is rated at 0.3 ohms and the E11K, also from FiiO is rated at less than 0.3 ohms also. It will be interesting to see how it performs with IEMs overall though the high DNR and THD+N rating should help. As such you cannot term this primarily as an IEM amp though I think given the size a lot of IEM users would want to give it a shot.

The pot is a stepped attenuated gain control with 21 steps and with decent physical resistance also. 21 steps is more than enough control given that the Ruby doesn’t have huge dollops of power so I would consider that suitably accurate for subtle volume changes.

It is also one of the better ones for balance control with very little left or right emphasis at very low volume levels which is usually a challenge for analog designs, particularly with IEMs.



The back keeps things simple with a micro USB charging port (not to be confused with any DAC functionality which it does not have) on the far left and in the middle you have a charging light that comes on during charging and turns off when the charge is complete.

To the far right, you have the on/off switch though I was hoping the LED light would come on when turned on but it seems not to in this case. The switch is low profile and stiff enough to prevent accidentally turning it on and off when out and about.

Stacking Problems

Despite the miniature size stacking of the Ruby will provide a Tetris-like challenge. Spatially it is a cube and as such lacks the slim dimensions of say an Oppo HA-2 or a FiiO E12 to stack smoothly with a DAP or phone.

Straps will not work that well either given the small surface dimensions of the top and bottom. The volume knob is also rather large and tight against the input and output jacks meaning slim profile jacks are mandatory to fit and even then they nestle in tight against the pot making everything a touch too cramped.

Most of the time I had it beside the X7 for instance rather than under or on top. I suggest grabbing a little bit of Velcro and sticking it under your DAP of choice and on top of the Ruby and place her right where you want it for cable connecting for the best solution.

The Package

Small amp, small package and nothing spectacular but what comes with it is good enough for $99 with a small hard case, USB cable and 3.5mm analog IC. Technically you could probably fit the Ruby in an IEM case of choice and still have room for the IEM and some tips and the IC.

The case itself is reminiscent of a decent IEM case anyhow so it doesn’t take a leap of imagination on how to get your ‘on the go kit’ packed up and ready to go. The USB cable supplies a standard 5v USB charge to the Ruby and it charges relatively quickly to max within 2-3 hours and that gives you a 12 hour playback time max. Tests had that relatively close in real-world usage.

Sound Impressions

Tonality & Bass

Tonally the Ruby has a warm to neutral presentation with a full sounding and forward mid-bass and decent punch but lacking in any huge sub-bass extension. Detail and resolution are pretty decent but it is not an overly analytical signature erring more to a musical quality than anything sterile or flat. Lower mids are relatively beefy also and in line with the mid-bass response. IEM’s with good low-end kick like the Shure SE846’s bass response do rather well with Ruby’s bass qualities.

Mids and Treble

The Ruby’s upper mid and lower treble range is not as convincing as the low-end performance with a slightly brittle and thinner signature and a little 5-7k peak which gives off a touch of glare on percussion and high synth work. Vocal presence is also back in the mix a touch and doesn’t stand out as much as the low end so whilst it is certainly not lost or recessed vocals do feel they are competing with everything else giving off a slightly congested feel.


The soundstage is more wide than deep with roll-off on Ruby’s upper treble extension and sub-bass reach and a strong focus on the lower mid-range. Imaging is ok with good left-right separation but there is a slightly more closed-in feel to the Ruby so it doesn’t have the most spacious or airy signature – think mosh pit rather than an arena.


Overall the Ruby feels like a good little musical analog amp that will suit modern genres with a bit of bass work and mid-range crunch. Those looking for something a bit flatter, more analytical with bit more space might do better to try out Ibasso’s D-Zero MK1 for a similar price and tends to be a bit brighter and more ethereal sounding.

The Ruby is more at home with mid-tempo rock, thrash guitar workouts like Megadeth’s Symphony of Destruction, beat-heavy work from LMFAO and Rancid’s guttural punk tones than Max Richter orchestral works or Sting fragile acoustical musings.



Noise and Lack Thereof

Despite its 2.5 ohm rating, the Ruby did very well indeed with sensitive IEM’s using line outs from the FiiO X7 and the DX90 from Ibasso. No discernible noise levels and hiss even from the notoriously fickle SE846 was kept to a very low level indeed.

Left/right channel balance was very minimal on the analog pot with both the SE846 and the Westone W4 at low listening levels which I think is something Stoner Acoustics can beat their chest about as some of the higher-priced analog amps out there have a bit more imbalance than this one.

Comparing the Ruby directly with the FiiO Q1 and E12 the background far nosier on the two FiiO amps when used in analog mode, especially with the SE846.

Double Amping

I would not recommend double amping the Ruby through headphone jacks as there was a discernible loss of power and quality compared to dedicated line outs even with sensitive IEMs. The Ruby can and will perform at a higher level through sources with dedicated line outs.

Plugging into the FiiO M3, for instance, required a huge jack-up in volume and the Ruby pot was very quickly past noon. Better to just stick with the M3’s only highly fun and smooth sounding internal amp. Double amping fared somewhat better with my BB Passport but the dynamics and clarity felt a bit muted compared to the FiiO DAP line outs (which should be a surprise really).


The Ruby has reasonable power to drive the more efficient planars such as the HE400s and the Oppo PM-3 but there is a loss of dynamics and resolution as a result. If you have to pick one, I would go with the PM-3 just for that nice sense of balance.

The HE400s mid-range still sounded smooth and flowing but the thinner top end of the Ruby made everything slightly brittle and off timbre wise with the HE400S. The Ruby fared much better with dynamic headphones such as the Nad HP50 and the Sony MA900 which are pretty easy to drive and in the case of the MA900 reasonably forgiving.

Our Verdict

The Ruby by Stoner Acoustics is one of the stranger yet undeniably cute audio offerings out there and though it is basically a portable analog amp it’s size and shape is very eye-catching. Throw in a quality if rather large pot, superbly low noise levels, and excellent efficiency and you have a nice little budget IEM analog amp with good, if not groundbreaking musical sound quality.

It is a difficult one to stack though and don’t even bother throwing your LCD-2 into it on the go it just doesn’t have the raw power. FiiO and iBasso though have some excellent, if a bit more mundane and conventional, budget digital amp/DAC’s such as the E07k and the newer Q1 but the noise on these amps are higher and less suitable for IEM’s.

You do get a DAC thrown in with FiiO amps and a lower profile stacking option but if you throw the Ruby on a desk beside the FiiO the FiiO is going to be largely ignored in a rush to see what this little cube can do. Perhaps this is the calling card, the big strength and what will provide ample queuing to try it out in the stores.

$99 is a reasonable price for the uniqueness of it all and it’s just, and only just, in the confines of budget amping. I do hope there is a second version to come out with a bit more tuning in the top end and maybe a smaller pot. Go all JH on me and give it a name like the Sonya or the Carrie and go silver also, the mind does wander a bit.

Technical Specifications

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

Size : 51(D) x 32(W) x 32(H)
Weight : 50g
Battery life : >12 hours at normal listening level
Charge : Standard Micro-USB 5V
Warranty : 1 year (no warranty for accessories)
Package Included : 1 x Ruby, 1 x Bag, 1 x Micro USB, 1 x mini-jack 3.5mm to 3.5mm cable.
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