To see what we finally have from the statistical point of view, I tested the first production panel with 10pcs 9039S PCBA. Each DAC was tested with a Windows PC USB3 port + 2m good fully featured USB2 cable for close to real-life conditions. 16ohm loaded(Cosmos Load-board has 16.1ohm yet) results would be better with a shorter cable + powerbank and so on(see Archimago's review). Cosmos APU LNA 34db for the DR test, Cosmos APU notch +6db for the THD+N tests, and THD test used APU notch 0db.
Averaged results for 10 samples of the table above: 32/96 DR AVG = 130.32db(A), No load 32/96 0dbfs THD+N AVG -125.66db, 32ohm loaded 32/96 0dbfs AVG THD+N -124.77db, 16ohm loaded 32/96 -.5dbfs AVG THD+N -122.935db.

 Interestingly, for the kind of Sine_gen mode(MCLK = 24MHz 1db higher noise but less harmonics, you can set that with Tweak_9039.exe CLK_GEAR=1) THD compensation coefficients are nearly zero(between 0 and 4), and all samples have at least one channel with all harmonics <-150db! This is a great opportunity for DIYers with Cosmos APU to measure their poweramps with 9039S as a balanced sine source(unbalanced is also not bad THD+N down to -121db) with no wasting $30000 for a noisy analyzer. 

 10kHz performance is remarkable too: 0dbfs H3 -135db, -3dbfs H3 -140db(probably limited by Cosmos APU performance!), BW90kHz THD = -132db, THD+N -116.3db.

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 9039S is mainly DIYer2DIYers product but isn't totally, unlike Cosmos APU or Scaler. Let's then talk about why 9039S is a remarkable leap for the portable DACs "industry". A portable DAC is intended to work with headphones, without it that device has no any sense. This is the same as a truck supposed to be loaded 24/7, hence, there is no sense in testing that with no load. That's crazy, but I didn't see any review based on measurements where a DAC+HPA or even a dedicated HPamp was rated by the THD+N(aka sinad) under loaded conditions. Thanks to our curiosity which may bring us to the end of such a review and we can see how -125db of sinad degrades to -115db at 16-32ohm of load even with standalone AC-powered HPamps, in the best case! I didn't see the result <-115db@16-32ohm ASR or L7 reviews, did you? Much worse for portable DACs, you can find there -80db(like 14bits) or so, and I should consider that as a technology state for 2024 because of 4.4mm jack? Simplified DAC tests let manufacturers "optimize" the product cost dramatically. If nobody cares about the real load testing why they'll add a heavy steady power supply in a portable DAC? Just 10uF ceramic SMD is Ok for that i.e. hundreds of times cheaper than 4500uF in 9039S. No reason for tens of PCB polishing iterations as well. 

 As you can see in the table above, 9039S no load(10 samples AVG 125.66db) vs 32ohm loaded has less than 1db of sinad difference, and 1.6db vs 16ohm loaded(about 700mW per channel). BTW, the full-scale modulation of ES9039Q2M noise is 2db only, "no hidden catch, no strings attached" just true DA conversion.
In fact, only one chip CS431**  dominates in portable chi-fi DACs within $13..299 range, with very fishy DR specs. I'll not claim that they implemented a tricky DR test deceiving algorithm(like DRE of ESS) or just CS431** has abnormally high modulation noise but for both cases, I wouldn't consider that DAC as a Hi-Fi at all, not mention of funky 384k "support". An experienced DIYer will recollect the Cirrus's hit from 2000 CS4398 DR 120db(A) and Fs <216k ;) I would like to try AKM DACs but they are about a decade in standby, so, vive la ESS. ES9039Q2M is a really gorgeous beast for reasonable money!

 Alright, it is clear that the performance is awesome as supposed to be but what about the drawbacks? Oh yeah, 9039S has it more than I wish.

 The first is a relatively high current draw 145-150mA and the DAC runs a bit warmer than 9038D6K, for example. The reason is serious opamps and 6.25V rail for them with low-noise 3.6MHz SMPS.

 Next, the pop noise is slightly louder than 9038D6K, the reason is composite opamps and parts tolerance. It's hard to explain that simply but a composite is two opamps in serial to obtain a huge loop gain(which is a factor of reducing the distortions), any charge of caps difference multiplied by hundreds of millions of times turning a fraction of uV to a volt.

 One more limitation caused by composite opamp usage is a max cable capacitance <6800pF. If you take a cable (DAC2HP) 5-10m the composite amp could start oscillating by losing loop stability. For that reason please avoid plugging/unplugging the cable with the powered DAC.

 Another "weakness" is 2.5mm output jack. As I read in ASR forum - "chi-fi industry" switched from 2.5 to 4.4mm or even XLR but I have no idea why, 9039S got THD+N -123db@16ohm(from 3 to 50x times better than any portable DAC with 4.4mm) with 2.5mm jack and it wasn't a bottleneck, by the way. Anyhow, for believers, we prepared a good quality adapter 2.5/4.4mm.

 As usual, we prepared for the DAC some control SW. Tweak_9039.exe app for Windows can control the type of 8 interpolation filters(for 9039S DAC1 only is active), volume, H2/H3 harmonics compensation(you can calibrate your DAC with Cosmos APU), and a few registers of ES9039 directly. IDAC_NUM default value = 0, the description you can find in the ES9039Q2M.PDF datasheet, I keep that reg controllable because some of the numbers(for instance 11) turn the DAC in NoOS mode or something like that. The mod isn't documented in the datasheet but investigated in the Archimago's review. CLK_GEAR reg switching the MCLK frequency, default value = 0 i.e. "49MHz", set it to 1 to get "24MHz" MCLK to minimize harmonics but 1db increasing the noise performance. DPLL_BW is the Digital PLL Bandwidth, active only for asynchronous FW like 9039S_v05.hex, less value = less jitter. Synchronous FW like zatoichi_v02.hex ignores that reg, and provides the best jitter performance, however, USB audio bridge CT7601 doesn't support native DSD in a sync mode, DoP64-128 only. 

 Tweak_9039.exe uses the USB HID interface which isn't supported by ios, moreover, ios17 ignores our USB devices if they use the HID. For this reason, I have to prepare 2 extra FW for ios17: 9039S_v05_noHID.hex and zatoichi_v02_noHID.hex. All Tweak_9039 parameters will be memorized independently and 9039S will keep them after FW reflashing. 

Please remember, the reflashing process is critical for interruption, a DAC could be bricked. Please use a good-condition USB cable and do not touch-shake it during reflashing.

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 Thanks Archimago for the comprehensive review 

 

 The Windows driver is here  Isn't necessary for W10/11 but for FW reflashing.

 

 Tweak_9039 windows app

 

 FW tool for Windows
 

 9039S FirmWare files

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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