I know some folks have been awaiting the results for the Light Harmonic Geek Out V2. As you know, I have already provided a bit of a preview a few weeks back so no need to say much more I think. Generally my feelings about this device have not changes over the weeks... The 3D printed plastic smell has completely dissipated by now. It does sound great and I must say, going into the measurements, the impression was that this is some of the best sound I have heard from these little USB devices! Remember, this is a $235US unit I got as an "early bird" off the Indegogo promotion.
Let's see if the measurements are consistent with some of my early subjective impressions.
Part I: Digital Oscilloscope, Impulse Response, Digital Filters TestOkay, let's start off with the usual 1kHz 0dBFS square wave off the headphone output at the default 100mW (at 16-ohms) setting:
That's encouraging. Excellent channel balance! About 875mV peak output. Clean, voltage-stable square waves. Of course we'll need to press the high-power output toggle button and see how the 1000mW setting looks like:
Voilà. An immediate increase to 3.1V peak (2.2Vrms). Or about an 11dB gain. Again, we're looking at excellent channel balance. One of the best I have ever seen whether USB "stick" type DAC like the AudioEngine D3 (excellent balance) or AQ Dragonfly (not great) and better than the ASUS Essence One from last week and some other desktop self-powered DACs I have come across! Output impedance is spec'ed at 0.47ohms. (I see the spec sheet talks about maximum output of 4Vrms, I imagine this must be using the balanced output with the proper TRRS cables with about a +6dB gain.)
How about impulse response? Remember there are 2 digital filter modes - default "TCM" (Time Coherence) minimum phase and "FRM" (Frequency Response) linear phase... Here they are:
Alright then. TCM is basically a standard sharp minimum phase filter, FRM is a weak anti-aliasing linear phase filter. Absolute polarity maintained.
And here then are the digital filter overlay graphs:
As you can see, the digital filter effects in the frequency domain are quite different between the TCM and FRM settings. TCM basically is a steep minimum phase setting with good suppression of aliasing. It doesn't "overload" even with 0dBFS wideband white noise unlike the ASUS Essence One or Samsung Note 5 shown previously - fantastic. I think this really speaks to the quality of the digital filter in the ESS SABRE in that it can handle the extremes of "intersample over" potential in oversampling digital processing. Furthermore the noise floor is really quite clean. This is essentially ideal behaviour for a sharp anti-aliasing filter for 44kHz signals.
The FRM is a different beast. It has a slow roll-off after 20kHz. Aliasing is evident with the mirror signal pairs at 24 & 25kHz. Noise floor is still excellent. Remember that companies like to show "clean" impulse responses with minimal ringing like the FRM in ads and promotional material. But there is a price to pay - less ringing generally means less aggressive filtering and higher potential for aliasing distortions; there's no free lunch. I think it's wise that Light Harmonic chose the TCM filter as default in this case and the listener is free to try the FRM mode to see if he/she prefers this alternate weaker filter.
Part II: PCM RightMark Tests & ComparisonsSetup:
Microsoft Surface 3 Pro --> LH Geek Out V2 (100 mW default setting) --> 3' shielded RCA --> E-MU 0404USB --> shielded USB --> Measurement Windows 8 computer16/44:
As usual, let me just show you the big numerical summary graph comparing the Geek Out V2 with a bunch of other DACs:
Notice just how close they all are in 16/44. The "least accurate" of the bunch would be the Dragonfly 1.2 but we're generally talking very small differences here. As I have shown in the past, the Dragonfly's stereo crosstalk is typically higher than most DACs I have seen.
Even though the Geek Out V2 TCM and FRM digital filters do function differently, they measure almost identically between 20-20kHz in this test. Remember, the aliasing may cause audible distortion due to non-linearities in a playback system like your speakers even though the effect is not appreciated in the electrical domain here when measured.
|Frequency Response. The Tascam is the one with slightly more low frequency roll-off compared to others.
Now we get a little more challenging... 96kHz is of course the peak samplerate for other small USB-powered DACs like the AudioEngine D3 and Dragonfly:
Again, no real numerical difference between the TCM and FRM settings. On the whole, we see that the noise level for these USB-powered DACs are a little higher than their larger desktop counterparts. Remember that I'm measuring the Geek Out V2 in 100mW mode... I bet the 1000mW mode would score even better in terms of dynamic range and noise level (unfortunately the high voltage level at 100% overloads my ADC).
|I zoomed into the top end a bit... Nothing much to see in the low bass. At most the DACs roll off -0.5dB at 20kHz so no big deal.
|Noise level. Notice the low level 60Hz hum with the Transporter.
Okay. Doubling the samplerate once more to 192kHz and we see this:
PonoPlayer in here as well - Pono's showing a bit more distortion and slightly higher noise floor but generally comparable. As above, the non-USB-powered desktop DACs have an advantage in the department of noise floor. I also included the Oppo BDP-105 here... This jack-of-all-trades Blu-ray player/DAC measures very well! Impressive!
|Frequency response. Again at 20kHz we're looking at most -0.5dB attenuation.
|Noise floor. The Pono and USB-powered Geek Out V2 appear to have higher noise level.
|IMD+N chart. Notice PonoPlayer's higher 2nd harmonic peak.
Part III: DSD64 & DSD128 Tests & ComparisonsEven though the Geek Out V2 goes up to 384kHz PCM, my ADC maxes out at 192kHz; I have yet to buy or download any music beyond 192kHz anyhow so the only value I see to this high samplerate is with software upsampling using one's own computer and disengaging the internal digital filter. But like last week, I can explore the DSD performance based on converting a 192kHz test signal to DSD64/128 and running it through the analyser to assess accuracy.
Like I did with the ASUS Essence One last week, this is with the KORG AudioGate software. Here's how it looks with DSD64:
Part IV: JitterHere are the Dunn J-Test spectra with both TCM (default) and FRM modes:
What can I say... Modern asynchronous DACs are generally immune to jitter issues as typically tested back in the day when the J-Test was constructed (and timing had to be extracted from SPDIF signals). This has been the situation for years with well engineered equipment.
Part V: ConclusionsNo need to belabour the point here guys... The Geek Out V2 is a well engineered and excellent measuring audio product. It is to date the best measuring "USB stick" type DAC I have had the opportunity to examine. As far as I can tell, there are no glaring flaws or issues from an objective perspective! In fact, I believe the measurements would be even better if I could measure the 1000mW high power mode if my ADC didn't overload at the high voltage. I think that's as good a praise as I can give for a device like this, not to even mention the reasonable price. Good job LH for making this and clearly putting energies into the design; particularly I suspect the choice of the new "flagship" ESS SABRE9018AQ2M DAC chip played a huge amount in the technical performance we see. As a perfectionist, I can quibble about the choice of digital filters (ie. no traditional sharp linear phase or slow roll-off linear phase with strong antialiasing). As per results shown previously, I do not believe that filter settings make a huge difference that would change one's enjoyment unless you start eating into the audible spectrum <20kHz like with the PonoPlayer at 44kHz samplerate. Besides, as a USB DAC that can handle up to 384kHz, you can "roll your own" filter setting with computer based upsampling using software like HQPlayer with the Geek Out V2; that could be fun.
Now as for subjective impressions, the 3D printed casing could be more refined (eg. more polished, less rough at places). However, as I said in my preview, the plastic resin material does keep the device cool to the touch even running in the high power 1000mW mode for hours - warm but not hot. Heat was noticeable with the metal construction of the AudioEngine D3 and I suspect the Geek Out V1 might have been similar. Also, I'm glad they put the red cap on the TRRS balanced connector to prevent potential equipment damage. I'll have a look at the balanced output performance if I have access to the proper cables one day.
I was impressed by the sound quality already in the preview article. This is "technically accurate", "high fidelity" sound, folks. The highs are high, lows are low, details intact, tonally neutral, dynamics powerful, jitter-free, channel separation and balance excellent. As a headphone amp, there's enough power to keep the volume up even with demanding inefficient headphones. The Geek Out V2 will not "euphonize" your music but present it as is; warts, "digititis" and all (I can recommend the AQ Dragonfly if you prefer a more mellow sound). Harsh sounding pop (like my copy of Duran Duran's Greatest - still fun of course!) will be fatiguing. But well recorded and produced albums - currently listening to tenor Jonas Kaufmann's recent operatic collection The Age of Puccini or earlier today Dave Matthews Band's Crash from 1999 (though dynamically compressed, have a listen to "Say Goodbye") - will be presented in full glory. Assuming the rest of one's equipment is up to the task, this is the kind of DAC that just "gets out of the way" in terms of objective transparency, exactly the kind of result which from an objective perspective I would like to see in all my high-fidelity gear.
My feeling is that if Light Harmonic even just took the base internal circuitry used here, put it into a nice enclosure, quiet power supply, provide RCA & XLR outputs, add a few more buttons, and indicators/display up on the front, we could see a technically unbeatable desktop DAC at an excellent price point (can we get this done <$500 with 2 big volume knobs up front like the ASUS Essence One?)!
I've never had a chance to listen/measure the Geek Out V1 but I can certainly say that the "second coming" has demonstrated just how fantastic sounding (and measuring!) inexpensive DACs can be these days.
Looking back on this past summer, it has been a bit of a measurement whirlwind! And gauging from the hits I'm seeing to the blog from all around the world through Google and Blogspot affiliates, I believe there's a huge amount of interest in objective analysis and a desire to actually understand and at least try to "know" how things work and what level of accuracy we can expect from devices like these DACs.
I found the recent "clock" incident involving the 14-year old kid Ahmed Mohamed interesting. Beyond the social concerns brought out in a case like this (ie. racial assumptions, culture of fear, educator incompetence?), it's good to see that "tinkering" and the joy of science (even something as "simple" as a digital clock these days) can still be found (especially encouraging when it's in our young people). Understanding the science behind all that we easily take for granted I believe is a basic foundation of living in a technologically sophisticated age; science is not magic, audio technology is not magic. The laws of nature help us differentiate the likely from the improbable or illogical. IMO anyone who in 2015 markets an audio high fidelity product without clear scientific justification and evidence (and I'm obviously not talking scientific-sounding "truthy" gibberish [Comedy Central classic video]) is sadly participating in promoting mysticism. As expressed previously, just having testimony isn't generally good evidence. Some people seem to find this kind of stance "close minded". I personally do not think that discounting magical thinking when it comes to engineered products is at all unreasonable, or obdurate.
I do hope that in time the mainstream "audiophile press" can find it in themselves to transform more into a medium of education (perhaps back into a medium of scientific education since I have found many articles from years past providing so much more substance). Of course I can accept a commercial component but it really is not a good sign when not infrequently substantial portions of "reviews" are simply comments lifted from company claims or interviews with company representatives with no evidence that the reviewer has any ability to question, or perhaps even understand such claims. It would be nice to see a day when the term "audiophile" regains respectability and represents a hobby interested in "high-fidelity" as it might apply to the hardware gear and assessment of recording quality; a hobby able to anticipate and promote advancement rather than appearing to be a cohort of consumers being marketed to (as demonstrated by Sony's ridiculous "premium sound" SD memory earlier this year).
Change is in the air. Welcome to the fall... Which for me also means work demands and upcoming overseas trips. Posts will get a little spotty over the next few months as a result.
Hope you're all enjoying the music :-).
Addendum: (January 30, 2016)
I can confirm that the output impedance is <0.5-ohms measured with a 1kHz signal and 20-ohm test load. Impressive!