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Review and Measurements of Cyrus soundKey DAC

amirm

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#1
This is a review and detailed measurements of the Cyrus soundKey portable USB DAC and headphone amplifier. It is on kind loan from a member. It costs USD $98.99 from Amazon with prime shipping. It comes in a few colors.

I like the flat form factor with detachable USB cord:

Cryus Soundkey Audio Review.jpg

I received two short USB cables, one of which you see in the picture above. I don't know if that is how Cyrus ships it or the owner sent it me as such.

There are no volume controls so you would be relying on your software player for that.

One of the differentiators for the soundKey is low power consumption according to the company. I will be measuring and reporting on that later in the testing. For now, there was no rise in the temperature that I could feel on the unit.

Audio Measurements
As usual, we start with our dashboard view of 1 kHz tone:

Cryus Soundkey Audio Measurements.png


Typical of these small dongles, there output is too low to use the soundKey as a proper DAC at 1.7 volts (like to see 2 volts).

Distortion numbers are disappointing with a SINAD (signal over noise and distortion) of only 76 dB. This is due to high second harmonic distortion. This puts the soundkey at the bottom tier of our rankings of all DACs regardless of type and price:

Best Audio DACs 2019.png


For a high-end company, I would have liked to see this distortion much more under control.

Turning down the input level a few notches did not improve the situation much.

Another down note was the roll off in low frequencies:

Cryus Soundkey Frequency Response Audio Measurements.png


I don't expect to see this in DACs/headphone amps.

Jitter spectrum was very clean but partially due to high noise floor:
Cryus Soundkey Jitter Audio Measurements.png


Linearity shows the soundKey to be fine for 16 bit audio (96 dB) but after that, there is a lot of deviation/lack of accuracy:
Cryus Soundkey Linearity Audio Measurements.png


Dynamic range likewise was "OK" for CD but not much more:
Cryus Soundkey Dynamic Range Audio Measurements.png


On the right we see the dynamic range when outputting just 50 millivolts into 600 ohm load. This is how it ranks against a few recently measured devices:

Cryus Soundkey Dynamic Range 50 mv Audio Measurements.png


Most important parameters for a headphone amplifier are power ratings versus distortion. Here it is at 300 and 33 ohms respectively:
Cryus Soundkey Power at 300 ohm Audio Measurements.png


Cryus Soundkey Power at 33 ohm Audio Measurements.png


The 300 ohm measurement shows a bit less power than Topping DX3 Pro in low gain. There is no clipping which is nice. Clipping comes our way though with 33 ohm load.

Putting these in perspective, we get:
Portable DAC Output Power at 300 ohm.png


Portable DAC Output Power at 33 ohm.png


Finally, here is the power consumption while idle and not:
Cryus Soundkey Power Consumption Efficiency Measurements.png


The soundKey is almost as efficient as Dragonfly Red.

Listening Tests
I started with my usual Sennheiser HD-650 headphones. Here, I was surprised that there was enough volume if you had recordings that were close enough to 0 dBFS. The sound overall was good and I could not detect much distortion even at max volume which is probably where the volume control will live.

Switching to Hifiman HE-400i was less satisfying. Bass performance was not there. And at high volumes I thought the highs got a bit distorted.

Conclusions
The Cyrus soundKey jumps into the crowded market of probable headphone dongles with good looks, form factor and functionality a volume control would have been nice though). On the down side, distortion metrics are poor. Better efficiency compensates for that if you use it on battery operated phones and such (you would need the Apple camera dongle for iOS support).

Listening test results were good with Sennheiser and not so good with Hifiman. The later probably suffered from rolled off frequency response and clipping distortion.

Overall, I am ambivalent about the soundKey. I see it a step up from $9 dongles but the $99 price is hard to swallow. I let you guys decide if it should, or should not be recommended.

------------
As always, questions, comments, recommendations, etc. are welcome.

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bakker_be

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#2
The cables you received are part of the retail package. I actually sent you everything but the package itself and its accompanying leaflet.
Subjectively speaking I like the SoundKey with my decidedly bargain-priced AKG K72's for late-night Netflix in bed and stuff like that, where it seems to be an upgrade for the built-in headphone out of my HP Elite X2 tablet. Various in-ears don't seem to suit it as well ...
It was the first dedicate headphone amp/dac device I bought, and it's from the Kickstarter campaign Cyrus used to launch it. I'm unsure however if it's really a Cyrus developed product, as I've since discovered the Ultrasone Naos as well (https://www.thomann.de/be/ultrasone_naos.htm?ref=search_prv_4), which at the very least looks identical, but boasts high-res capabilities. I haven't bought that one, so can't comment any further on it.
 

Veri

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#3
Possibly any measurement of output impedance? :)
 

confucius_zero

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#5
Isn't smsl idea better than this?
 
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#9
Funny enough I got an Email from these guys today to visit the private Showroom at AXPONA, had my eye's on the portable... after these measurements I can't say I'm surprised. Their website has a few lazy copy & paste's errors. Still to have low frequency roll off, low output and distortion that high... ugh no thanks!
 

Jimster480

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#10
Just seems way too overpriced for really poor performance.
I would say that most phones with headphone jacks will blow this out of the water already.... I mean the HTC dongle tested like 90db sinad and its like $10?
 

amirm

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#13
I'm not sure if that would actually affect the performance.
Correct. This is just a noise test, not distortion. I wanted to load the output down so it is not floating.
 
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#15
I see. If the output impedance is very low then the noise test between 600 ohm and 33 ohm won't make much difference. A few ohm at the amp output would change the noise level to make it lower with 32 ohm earphone.
 

bravomail

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#16
Speaka USB is not very good. 15 bits of linearity. I bought it, since it's cheap. It is strong, but distorts a lot. SMSL Idea is too weak, cannot drive my AKG K7xx properly, or maybe its SINAD of 90dB showed itself that way - didn't sound good to me. From all the dongles I had only one with positive results - Hifime Sabre 9018, strong, no noise, sweet sounding. From non-dongles, which I used as a dongle, SMSL M3 is very powerful, but has some distortion issues (muddy), also due to its power maybe it sounds harsh.
 

Roen

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#17
I feel like a Thumbdrive DAC / Amp Combo Thread needs to be started with a collection of all available units and their associated performance plotted on common axes.
 
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#18
Amir, I work as a designer with caraudio and pro-audio customers 12 years, and this industry uses another approach to measure Amps.
In my opinion, if a speaker/headphone amplifier under test it is a good idea to measure its SINAD at -3db(1/2 max power, where max power is the power where THD+N reached 1%), it's common practice if not a standard.
Yes, a DAC with the line outputs has to produce the best performances at 0dbfs level but an Amp has to amplify DACs signal up to clipping and more. I believe, every Amp on the market intentionally has some extra gain for that, perhaps excluding FDA/PowerDACs.
One more point, the DUT is powered by USB "5V" rail which actually seldom more than 4.2VDC under 100-300mA of the load, hence, 0dfs THD+N will strongly depend on USB port rail current limiter IC(like TPS2061C) setting.
Look, If that test will consider max power as the power where THD+N = 1% and SINAD will be measured at half of max power the soundkey will not look so shameful: [email protected] .006%, Power 80mW. I'm sure that approach is much more informative, and gives more clues to readers regarding the DUT.
BTW, I measured with AP2702 my old $300 chinese android Nubia Z11 3.5mm output with 1kHz 16/44.1THD+N .0015%(16b theoretical limit!) SNR -118dbA but actually there is AK4376 which is always On automute at -100db or about(good idea to test for that cheating is on or off, can it pass undetected under your radar?). The output power I guess is comparable with soundkey i.e useless for typical planar like my HFM HE400i.
 
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