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ES9038Q2M Board
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Old Today, 06:12 AM   #3901
Markw4 is offline Markw4  United States
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Agreed about bandwidth specification. What I was trying to get at is that the AKM graph showed AKM and ESS noise was about the same up to 50kHz. At that point ESS noise rises and at 200kHz or a little higher AKM noise starts to rise a little. They cut off the graph at 300kHz so we can' see anything after that. Does it matter? I think it might. The concern would be that HF junk that we didn't see when looking A-weighted might cause problems in other equipment such as power amps that may not adequately protected against it.

To try putting the foregoing another way, in regard to graph you linked to of AKM and ESS dacs, the noise was shown different primarily from 50kHz to 300kHz. Still don't know if it works the same way for DSD. Also, don't know if A-weighted measurements can show much in the HF band that AKM says they are proud of. We don't know what AKM DSD may be doing up there if we measure A-weighted, for example. In a similar vein, if we only care about A-weighting, then the fact the ESS gets noisy only starting at 50kHz may be completely irrelevant since it is above where A-weighting cares about.

Sorry, but for some reason I seem to be having trouble organizing what is nagging at me about what we have been discussing. Hopefully, I am starting to get more clear about it.

Last edited by Markw4; Today at 06:17 AM.
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Old Today, 06:32 AM   #3902
IVX is offline IVX  Ukraine
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Markw4, I've no idea what DAC is blue plotted there, probably some ESS, maybe some CS**** or Ti DAC. If you have a DSO with FFT you may check that noise on your own board, it's would be very interesting to know is that bad or ok or even good.
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Old Today, 06:54 AM   #3903
Markw4 is offline Markw4  United States
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Right, I did make an unnecessary assumption about the blue graph, but it is kind of irrelevant to the issue about A-weighting vs at what frequencies is noise actually important. If noise is important well above A-weighted frequencies, then what bandwidth do we consider important and what noise level are we willing to say is okay? If the blue line dac has noise the same as AKM up to 50kHz, who cares above that, nobody could hear anything bad from it (if we are using A-weighting as a standard or proxy for frequency bandwidth that can cause audible problems).

In the meantime, I do take your point re trying to measure the ES9038Q2M dac noise. However, don't think that will be easy at this point. The dac is down in a shielded enclosure, and the dac outputs are held at a fixed voltage by the I/V opamps. Even trying to measure HF/RF at the I/V outputs would probably be too difficult without removing the dac from the enclosure which I am not ready to do.
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Old Today, 07:14 AM   #3904
IVX is offline IVX  Ukraine
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no problem, next couple weeks I'll build my PCBA and test out of band noise for SE9038Q2M, that'll take 5min
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Old Today, 07:45 AM   #3905
eziitis is offline eziitis
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Quote:
Originally Posted by IVX View Post
If someone doesn't mention A-weighting, he has to specify the BW at least. Do you believe if ES9038Q2M has S/N=DR= -129db unweighted with 3.3VDC power and 25C ambient? Single one resistor 330ohm@25C should produce in 20-20k BW -129db(or about -132dbA) S/N regarding 1VRMS, if ES9038Q2M has -129db unweighted I'll be surprised. I saw this morning AKM mobile 3.3V DAC with -125dbA DR but with "Auto-mute gate" i.e. when the input data < threshold, DAC simply off and that state shows -125dbA. Higher class DAC, 4490 as well, has 5V power.
what do you mean with "AKM mobile"? in real life it was quite an effort for TEAC to get SNR down to -110db for their 503 DAC as they say. according to AK specs 4490/4493 figs are -120/-123 dB
one of the best "kind of DIY" implementation of AK4490 Lynx d78 managed to get bellow -115dB within 50kHz for 0dB 24bit PCM with quite a bit filtering.
IMHO there is no question whether LPF or not, it is rather the features of it. perhaps 3rd order Bessel might be sonically the best
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Old Today, 07:59 AM   #3906
IVX is offline IVX  Ukraine
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this one is mobile https://www.akm.com/akm/en/file/data...AK4376AECB.pdf They claim -125dbA but actually, there is 116dbA. TEAC got THD+N at -110 or .0003%, it is probably not too easy for 4490 but S/N -110dbA is a trivial task even for DIYers.
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Last edited by IVX; Today at 08:03 AM.
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Old Today, 08:34 AM   #3907
eziitis is offline eziitis
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indeed, and you are suggesting to get rid of post DAC LPF to make this really trivial?
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Old Today, 09:38 AM   #3908
IVX is offline IVX  Ukraine
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110dbA S/N on 4490 is trivial regardless LPF on/off the board. I keep in mind the opportunity to simplify the DAC board and finally save PCB area(my se9038q2m project is DAC->HPA USB dongle).
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Old Today, 10:21 AM   #3909
eziitis is offline eziitis
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well, I can not really see the purpose of arrea saving efforts and all the attempts to simplify the design, because in this way one will end up with something on par in SQ with a decent computer onboard audio at best (e.g. ALC885), whatever the A-weighted dB number will show up.
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