One perhaps good thing, as it goes back together is that it gives me a chance to reconsider how I did some of the assembly and where I located things first time around. Don't know if I can do any better, but I will see if I can think of anything to make better before starting in doing the actual assembly.
Fortunately, there not all that much to do either. Most of the original work was in constructing the boards, whereas attaching them and soldering a few connections is only a small part of the whole.
I have some other stuff going on around here for a couple of days too, so maybe Monday or Tuesday before moving forward again, or maybe sooner just have to see.
Fortunately, there not all that much to do either. Most of the original work was in constructing the boards, whereas attaching them and soldering a few connections is only a small part of the whole.
I have some other stuff going on around here for a couple of days too, so maybe Monday or Tuesday before moving forward again, or maybe sooner just have to see.
Vinny's driver is well worth trying..... I hadn't realised it was out.....must have fallen out of the loop....
@eslei.... pm me again....lost your last one to a crash...
Hello guys,
Would this be a good place to start for me to build my DAC? Is it realistic for someone with very limited knowledge to upgrade this with better parts? I want to start somewhere and the chassis included is a bonus for me as I don't have a lot of access to metal work tools.
ES9038 ES9028PRO ES9018 DAC audio decoder Amanero USB interface Support DSD coaxial optical with Remote Control Shield USB cable-in Digital-to-Analog Converter from Consumer Electronics on Aliexpress.com | Alibaba Group
Would this be a good place to start for me to build my DAC? Is it realistic for someone with very limited knowledge to upgrade this with better parts? I want to start somewhere and the chassis included is a bonus for me as I don't have a lot of access to metal work tools.
ES9038 ES9028PRO ES9018 DAC audio decoder Amanero USB interface Support DSD coaxial optical with Remote Control Shield USB cable-in Digital-to-Analog Converter from Consumer Electronics on Aliexpress.com | Alibaba Group
How long is a piece of string...? How limited is 'very limited knowledge'...?
The Weiliang / Breeze Audio ready-built DAC solution you've chosen has four distinct builds based on a choice of DAC chips and output stage chips:
Bundle 1: ES9018 [FONT=arial, helvetica, sans-serif]+ 2pcs 49720+2pcs49710[/FONT]
Bundle 2: ES9028 [FONT=arial, helvetica, sans-serif]+ 2pcs 49720+2pcs49710[/FONT]
Bundle 3: ES9028 + 2pcs 8920+2pcs797
Bundle 4: ES9038 + 2pcs8920+2pcs797
It is not clear whether the Seller/Manufacturer's choice of DACs is covering the Q2M and PRO DACs over the whole range of bundles (possibly not ES9038 PRO as it is quite pricey...) The voltage regulation is probably based on LM78xx and LT1963 regulators which is JUST fine as it is but can be improved upon (depending on the said skills).
You would need to decide yourself which solution to choose by perusing:
- the current thread
- Sergelisses' thread ES9038Q2M Production
- Mikett's thread Moving from 9038Q2M to a 9028Pro board
...plus a lot of info (documentation and pictures) needs to be obtained from the Seller unless there is somebody else who has already purchased one of the bundles and has initiated some level of modding... and is happy to share his/her experience.
On the other hand there are some quite decent USB DACs out there with a quite reasonable follow-up on the Internet (comparisons. reviews, etc) in the same price range: Topping DA50 / SMSL M8A / HiFiMe UDA38PRO. There is also some level of modding done starting with better power supplies, etc.
A lot of pondering before parting with your cash... Good luck!
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Hi Alex,
The dac board inside the case in the pictures at that link you gave looks very similar to the one Mikett has been working on in his thread: Moving from 9038Q2M to a 9028Pro board
If you read all of Mikett's posts in his thread and in this thread I think you will find he started out with one of the boards in this thread, had some mishap with it and decided to go with a different board.
If I recall correctly, he thought the new board like you are thinking of getting would require fewer modifications to be improved to his satisfaction. So he did some mods and stopped there. More recently I think he may have decided to do a little more on it.
Actually, he will probably see these posts before too long and maybe comment for you as well.
I guess my own feeling is that if you start out with a cheap dac board like we mod in this thread, you aren't risking much money and you stand to end up with a very good dac for what you spend. If you start out with a more expensive dac, most of the same things still could use modding to bring them up to the sound quality level we use here with the cheap dacs. Maybe a little less work starting with a more expensive dac board. Don't know how the ultimate sound quality compares since no one every gets them together in the same room to A/B compare.
The dac board inside the case in the pictures at that link you gave looks very similar to the one Mikett has been working on in his thread: Moving from 9038Q2M to a 9028Pro board
If you read all of Mikett's posts in his thread and in this thread I think you will find he started out with one of the boards in this thread, had some mishap with it and decided to go with a different board.
If I recall correctly, he thought the new board like you are thinking of getting would require fewer modifications to be improved to his satisfaction. So he did some mods and stopped there. More recently I think he may have decided to do a little more on it.
Actually, he will probably see these posts before too long and maybe comment for you as well.
I guess my own feeling is that if you start out with a cheap dac board like we mod in this thread, you aren't risking much money and you stand to end up with a very good dac for what you spend. If you start out with a more expensive dac, most of the same things still could use modding to bring them up to the sound quality level we use here with the cheap dacs. Maybe a little less work starting with a more expensive dac board. Don't know how the ultimate sound quality compares since no one every gets them together in the same room to A/B compare.
Hi Alex, Mark is correct. I got my DAC going and truth be told, the stage it is at right now. I would be perfectly happy were it not for the tinkerer streak in me at this point.
I am more convinced I am on the right track after just having come from the concert hall last evening and listening this morning and I am impressed.
The board contained within the DAC link you provided is extremely likely 99% sure is the same DAC board I chose. In my mind this is a good value board, not the best but a good compromise given the cost. I chose to stick with the 9028pro because the current output of the DAC is something that stock op amps can handle comfortably. I stayed away from the 9038PRO for that reason despite the extra performance that is potentially there except how would one handle the AVCC output comfortably.
Depending on your source, your experience might be different but I found that using an XMOS USB input was superior to using Coax and coupling it with the SRC4392 resampler and rate converter so that is where I am at this point.
For the digital sides, I disconnected the LT1963s by not powering up that line but attached two separate LT3042s to the output lines of the LT1963s. These LT3042 are current boosted circuits where the 3042 drive the transistors at unity gain. One ouput directly powers the clock as well as DVCC on the DAC. The other 3042 is powering the AVCC lines. Here, I installed a 470uF OSCON low esr cap and down the line I installed some 47uF tantalums. Both LT3042 have 22uF Cset on board. I have no problems on startup.
For the Analog side, I decided to go with the OPA 1612 op amps for the first IV stage and installed the OPA1611 for the differential amp output. These op amps are better able to sound less constricted and the sense of power and openess is there as compared to the LME49720/LME49710 on this board.
I also installed extra ceramic by passes on the IC power lines for each op amp and this helped smooth out the sound.
I also removed the LM317/337 regs for the analog side and instead led the rectified and smoothed voltage to a higher performance Sulzer regulator I had left over from prior projects.
Changes yet to be made as time permits. All parts in my possession now!
Change the clock to a Crystek. There is supposed to be pads under the tin can osciallator that fit the Crystek clock.
Install high performance hybrid op amp consisting of a LME49710 - LME49600 op amp for the AVCC lines. Here I will remove the LT1963 and solder on the LME49600 in its place only contacting ground and the voltage out.
Power up the LT1963 line but cut the trace leading to the clock.
Power the clock directly from the LT3042.
Try laddering some mid value film caps on AVCC in parallel with the tantalums.
I will also install a LTC6655 as the voltage reference I am considering powering this from a real Jung SuperReg circuit that will also power the AVCC hybrid op amp.
On the Analog side, I will install a set of set of Jung SuperRegulators and reinstall the Lt317/337 as preregulators but reconfiguring the resistor to allow a high voltage output to the SuperRegs.
The output traces will be sut and lead out to the super reg.
The input back to the analog power supplu line will be fed from the SuperRegs on the other side of the cut.
I also plan to raise the output voltage for the OPA1611 and OPA1612 to 17 volt rails.
The extra LT3042 freed up from my current build will be feeding the XMOS circuit via a modified USB cable...or possibly I will feed it directly from inside the DAC.
All the transformers for these circuits will be external in a separate enclosure.
I plan to make low impedance leads to the circuits offboard by using heavy copper foil encased in tough mylar tape . This will allow low inductance leads and if enough foil is available I can sandwich it in between ground planes to minimize noise.
The only circuit building is stuffing the superreg boards from DIYAudio store. The hybrid op amp will be built by bending leads and point to point construction and soldering directly to the board.
Remember that my DAC board started as $137 including a remote. This board provides as well as the rectifying stages for the required voltage lines and you get a PRO series DAC.
Whether or not the PRO sounds better right off the bat, is open to question but someone has reported it does. Another thing to consider is that the PRO series has an autocalibration feature for the AVCC output. I am not sure if the mobile version has that feature. Undeniable is that the potential for superior sound is there however if one can reap it.
One will notice that I have dedicated some effort on the analog side because over decades of listening op amps PSRR to me don't tell the whole story. High performance supplies to op amps do sound different when a system can resolve it. That is my finding since the 80s. Even the IC guru Walter Jung who wrote IC OP amp cookbook will recommend high performance power supplies for Op amps in audio circuits if you want to max out. YMMV.
Building is one thing but having been DIYing since the 70s I am always looking at how this all fits together. I don't like obvious DIY builds. I always want something that ends up looking decent.
With that in mind, I acquired a board and an enclsoure for the DAC separately and then got another enclosure for the power supply. It is surprising how much money the lowest tech items like a case costs. but that is what it is. So all my mods fit into the same enclousre in your link BUT the power supplies are housed in a larger external case.
I am more convinced I am on the right track after just having come from the concert hall last evening and listening this morning and I am impressed.
The board contained within the DAC link you provided is extremely likely 99% sure is the same DAC board I chose. In my mind this is a good value board, not the best but a good compromise given the cost. I chose to stick with the 9028pro because the current output of the DAC is something that stock op amps can handle comfortably. I stayed away from the 9038PRO for that reason despite the extra performance that is potentially there except how would one handle the AVCC output comfortably.
Depending on your source, your experience might be different but I found that using an XMOS USB input was superior to using Coax and coupling it with the SRC4392 resampler and rate converter so that is where I am at this point.
For the digital sides, I disconnected the LT1963s by not powering up that line but attached two separate LT3042s to the output lines of the LT1963s. These LT3042 are current boosted circuits where the 3042 drive the transistors at unity gain. One ouput directly powers the clock as well as DVCC on the DAC. The other 3042 is powering the AVCC lines. Here, I installed a 470uF OSCON low esr cap and down the line I installed some 47uF tantalums. Both LT3042 have 22uF Cset on board. I have no problems on startup.
For the Analog side, I decided to go with the OPA 1612 op amps for the first IV stage and installed the OPA1611 for the differential amp output. These op amps are better able to sound less constricted and the sense of power and openess is there as compared to the LME49720/LME49710 on this board.
I also installed extra ceramic by passes on the IC power lines for each op amp and this helped smooth out the sound.
I also removed the LM317/337 regs for the analog side and instead led the rectified and smoothed voltage to a higher performance Sulzer regulator I had left over from prior projects.
Changes yet to be made as time permits. All parts in my possession now!
Change the clock to a Crystek. There is supposed to be pads under the tin can osciallator that fit the Crystek clock.
Install high performance hybrid op amp consisting of a LME49710 - LME49600 op amp for the AVCC lines. Here I will remove the LT1963 and solder on the LME49600 in its place only contacting ground and the voltage out.
Power up the LT1963 line but cut the trace leading to the clock.
Power the clock directly from the LT3042.
Try laddering some mid value film caps on AVCC in parallel with the tantalums.
I will also install a LTC6655 as the voltage reference I am considering powering this from a real Jung SuperReg circuit that will also power the AVCC hybrid op amp.
On the Analog side, I will install a set of set of Jung SuperRegulators and reinstall the Lt317/337 as preregulators but reconfiguring the resistor to allow a high voltage output to the SuperRegs.
The output traces will be sut and lead out to the super reg.
The input back to the analog power supplu line will be fed from the SuperRegs on the other side of the cut.
I also plan to raise the output voltage for the OPA1611 and OPA1612 to 17 volt rails.
The extra LT3042 freed up from my current build will be feeding the XMOS circuit via a modified USB cable...or possibly I will feed it directly from inside the DAC.
All the transformers for these circuits will be external in a separate enclosure.
I plan to make low impedance leads to the circuits offboard by using heavy copper foil encased in tough mylar tape . This will allow low inductance leads and if enough foil is available I can sandwich it in between ground planes to minimize noise.
The only circuit building is stuffing the superreg boards from DIYAudio store. The hybrid op amp will be built by bending leads and point to point construction and soldering directly to the board.
Remember that my DAC board started as $137 including a remote. This board provides as well as the rectifying stages for the required voltage lines and you get a PRO series DAC.
Whether or not the PRO sounds better right off the bat, is open to question but someone has reported it does. Another thing to consider is that the PRO series has an autocalibration feature for the AVCC output. I am not sure if the mobile version has that feature. Undeniable is that the potential for superior sound is there however if one can reap it.
One will notice that I have dedicated some effort on the analog side because over decades of listening op amps PSRR to me don't tell the whole story. High performance supplies to op amps do sound different when a system can resolve it. That is my finding since the 80s. Even the IC guru Walter Jung who wrote IC OP amp cookbook will recommend high performance power supplies for Op amps in audio circuits if you want to max out. YMMV.
Building is one thing but having been DIYing since the 70s I am always looking at how this all fits together. I don't like obvious DIY builds. I always want something that ends up looking decent.
With that in mind, I acquired a board and an enclsoure for the DAC separately and then got another enclosure for the power supply. It is surprising how much money the lowest tech items like a case costs. but that is what it is. So all my mods fit into the same enclousre in your link BUT the power supplies are housed in a larger external case.
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Oh, recently I discovered this power supply that people building these DACs could be interested in.
These are supposed to be superior to the LT1963. These could feed the op amps as well as AVCC circuits...not the AVCC 3.3V.
Don't know the circuit but it is using a 5534 ( New???? Come On!) possibly driving a FET with some transistors.
You'd need a twin coils and not a center tap transformer however. Most toroids are twin coils nowadays.
All three circuits seem to be the same. With just an adjustment trimmer.
I ordered one for curiosity and will power "something" around.
HIFI DAC Power Board Fever DAC Power Supply Board +- 12V 5V replace LT1963AEQ | eBay
Edit: OK, I figured this out. I will take my Dremel and cut off the third channel and use it to feed the AVCC hybrid op amp as well as the LTC6655. You can probably have as much voltage coming in as the 5534 can take about 36V DC. This could power up my upcoming Hybrid FET Tube Preamp running on 30-32V rails plus heaters.
These are supposed to be superior to the LT1963. These could feed the op amps as well as AVCC circuits...not the AVCC 3.3V.
Don't know the circuit but it is using a 5534 ( New???? Come On!) possibly driving a FET with some transistors.
You'd need a twin coils and not a center tap transformer however. Most toroids are twin coils nowadays.
All three circuits seem to be the same. With just an adjustment trimmer.
I ordered one for curiosity and will power "something" around.
HIFI DAC Power Board Fever DAC Power Supply Board +- 12V 5V replace LT1963AEQ | eBay
Edit: OK, I figured this out. I will take my Dremel and cut off the third channel and use it to feed the AVCC hybrid op amp as well as the LTC6655. You can probably have as much voltage coming in as the 5534 can take about 36V DC. This could power up my upcoming Hybrid FET Tube Preamp running on 30-32V rails plus heaters.
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Well we know you never what you'll get from the far east suppliers on ebay. In looking at the pics on the listings, two layouts are shown in listing for the same power supply. However what is interesting is that even the far east suppliers are now supplying relatively high end type power supplies using op amps. In the circuits shown, they appear to be generating the reference from the input voltage or is it from the output which is trickier but better. Also what are they using for the reference voltage? Can a higher performance op amp like the LME49710 be used instead of the NE5534? This board might have serious potential especially for the price asked, of course depending on how it performs...but this is the first time I have seen a real effort into making a more complex power supply rather than a packaged LDO on Ebay.
If it is decent enough it could be well worth powering up preamps etc. with this at a modest cost.
I'll wait for mine to see what this is all about.
If it is decent enough it could be well worth powering up preamps etc. with this at a modest cost.
I'll wait for mine to see what this is all about.
Hi again Alex,
So, there you have it from Mikett. As you can see you would be looking at improving the same areas as if you started with the board in this thread. You would be more on your own for AVCC (a super critical power supply), unless maybe Mikett beats you to it and can offer tips. Then there would be the other power supplies, the clock, and fixes of some extent or other to the output stage. Then, I would also recommend trying AK4137 whether or not Mikett decides to. Very different beast from the SRC4392 Mikett tried and decided not to use. I would also hook up an Arduino to control dac registers as there are some settings that can help there too. Regarding Arduino, if going with this thread, if you chose one of the green boards, probably v1.07, nothing difficult with doing that particular mod.
The total cost should be much less with the dac board in this thread, and sound quality can be virtually the same. It depends more on whether or not you do *all* the mods and some choices about exactly how you do them. All up to you.
So, there you have it from Mikett. As you can see you would be looking at improving the same areas as if you started with the board in this thread. You would be more on your own for AVCC (a super critical power supply), unless maybe Mikett beats you to it and can offer tips. Then there would be the other power supplies, the clock, and fixes of some extent or other to the output stage. Then, I would also recommend trying AK4137 whether or not Mikett decides to. Very different beast from the SRC4392 Mikett tried and decided not to use. I would also hook up an Arduino to control dac registers as there are some settings that can help there too. Regarding Arduino, if going with this thread, if you chose one of the green boards, probably v1.07, nothing difficult with doing that particular mod.
The total cost should be much less with the dac board in this thread, and sound quality can be virtually the same. It depends more on whether or not you do *all* the mods and some choices about exactly how you do them. All up to you.
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Turning attention back towards the through hole component project, it will probably still be a few days or later in the week before I am far enough caught up and ready to look at HD compensation with the new output stage. As long as I am putting things back together I think I want to do it just once if possible. Before I had in mind to make some changes in incremental steps to see how much SQ difference each change makes, but its too hard to do that here given the steel box I have to put the dac into for testing to keep local EMI/RFI at a low enough level. The way things are stacked up in the box it is tedious to put the dac in and take it out frequently. That's part of what got me in trouble recently, not the only thing, but a significant issue. Therefore when the dac board goes back in it will have a dedicated clock regulator and separate dedicated VCCA regulator (both pins!). In addition, it will have 22uf or 33uf film caps to try for the AVCC opamp output filters instead of 47uf aluminum polymer caps.
While we are talking about the through hole project, I know bih has not finalized the BOM he was working on for that yet. Also, don't know if anyone has started ordering parts yet anyway.
We did talk here briefly about a possibility of using Surfboards (or equivalent) and SMD resistors and caps instead of some of the leaded resistors and caps. If there are people who think that kind of SMD construction might be doable and of interest, I would encourage anyone to give it a try.
If enough people think they might want to go that way if given an option, maybe the BOM could be expanded to include parts for an SMD-on-adapter version.
If there is any interest for something like that, please raise your hand (figuratively) so we can see how many. Otherwise, we will stick with what we have already for the parts list, and only make a few corrections/updates.
While we are talking about the through hole project, I know bih has not finalized the BOM he was working on for that yet. Also, don't know if anyone has started ordering parts yet anyway.
We did talk here briefly about a possibility of using Surfboards (or equivalent) and SMD resistors and caps instead of some of the leaded resistors and caps. If there are people who think that kind of SMD construction might be doable and of interest, I would encourage anyone to give it a try.
If enough people think they might want to go that way if given an option, maybe the BOM could be expanded to include parts for an SMD-on-adapter version.
If there is any interest for something like that, please raise your hand (figuratively) so we can see how many. Otherwise, we will stick with what we have already for the parts list, and only make a few corrections/updates.
Sorry to hear that your DAC panel was destroyed. It seems, the VCCA pins are connected internally. We measured approx. 5 ohm in between of the two VCCA pins. The power both of the pins is a wrong idea, you need power only one of them. My green boards powered in this way and works just fine. To provide a separated power line to VCCA improves the overall presentation of the DAC too.
i have been using this for a while. it is a series reg with tl431 ref. and there is a number of other discrete low noise regs on ebay, like studer900 type etc.
if one is concerned about the noise of this ref, just add 2x RC and the noise in the audio range will be well below 140dB.
regarding other mods described i think that the clock deserves own reg as close as possible. also AVCC reg seems to be pretty far from the pins, and more filtering of Vref may be required.
Hi Janos_904,
Have to say I am curious about what you mean by improving the overall presentation? I am not familiar with the terminology. Thanks!
Mark,
In terms of pure measurement, can you quantify based on an order of magnitude improvement in THD based on your mods? For discussion purposes, if we use a starting point of .3 THD for the SMPcb ES9038Q2M stock board, do your mods progressively improve that to say, .03 or even further to say, .003? Is there a 10-fold level of improvement to be had? To be honest, I'm not sure I can even hear a difference between .03 and .003 THD!
I take it from some of your earlier comments, you are more inclined to rely on empirical measurements/evidence first, and then a subjective evaluation of a particular change, in terms of sonic characteristics - hopefully an improvement. I know there are many other factors in play, so I'm not asking you to be precise, just a general level of improvement that can be measured, and would be expected if implemented following your mods.
Knowing this information may help myself and others decide whether these are mods worth implementing. Discounting of course the pure pleasure and enjoyment of DIY projects, and how far some may be willing to go in their quest for sonic nervana.
In terms of pure measurement, can you quantify based on an order of magnitude improvement in THD based on your mods? For discussion purposes, if we use a starting point of .3 THD for the SMPcb ES9038Q2M stock board, do your mods progressively improve that to say, .03 or even further to say, .003? Is there a 10-fold level of improvement to be had? To be honest, I'm not sure I can even hear a difference between .03 and .003 THD!
I take it from some of your earlier comments, you are more inclined to rely on empirical measurements/evidence first, and then a subjective evaluation of a particular change, in terms of sonic characteristics - hopefully an improvement. I know there are many other factors in play, so I'm not asking you to be precise, just a general level of improvement that can be measured, and would be expected if implemented following your mods.
Knowing this information may help myself and others decide whether these are mods worth implementing. Discounting of course the pure pleasure and enjoyment of DIY projects, and how far some may be willing to go in their quest for sonic nervana.
measured approx. 5 ohm in between of the two vcca pins is correct. we need more information about power only one of them is ok. can you pls post a photo of your green board.
i experience that to provide a separated power line to vcca impoves the sq too.
redjr,
THD is a terrible way to measure anything, particularly a dac. There is lot more to them that can affect sound quality than just simple stationary HD. I did take my 1st modded dac board to Richard Marsh's who has some measuring equipment. He said all the harmonics are below -120dB, most of the down at -130dB or lower. Of course, if using DSD for playback, noise is probably going to be higher than for PCM. We didn't have time to do more as we spent a lot of time investigating some odd spurs down at -130dB. They mostly went away when I put my finger on the clock. Don't know what was going on there. I'm not seeing them now when I look at harmonics for HD compensation adjustment. Thing about measuring here is I can do it now if the dac is the steel file server case, which shields the EMI/RFI around here. Although the calibration is not perfect on that, it looked looked like the harmonics were still down around where Richard measured them. Of course, there are a number of other tests that really ought to be done for a dac.
EDIT: Also, when I did HD compensation in the dac registers for H2 and H3, I could only reduce them maybe a couple of dB each. One, H2, required a tweak of 5 out +-32,000 and H3 was lowest with a setting of -6. That distortion was minimized with almost no compensation is consistent with the distortion being down about as low as it can get with one of these ES9038Q2M dacs. It should be too, I have done pretty near everything I know how to do to make it as low distortion as possible.
As far as how I judge as I go with mods, whether they are taking it in the right direction, the wrong direction, or I can't really tell, I do that mostly by quick (or slow) A/B comparisons with DAC-3. Of course, DAC-3 always sounds better and more accurate. More like real instruments and voices, as well as more detailed. However, that is in near field listening at a very specific volume level. Walk to the other side of the room out of the near field and turn up the volume a little and it can be much more difficult or impossible for me to tell a difference. That's mostly because they are both very good Sabre implementations (with DAC-3 clearly better up close).
As far as whether or not you could hear the differences yourself, Earl Geddes, a hearing researcher and speaker designer who hangs out at diyaudio sometimes says that he can show an example of .01% distortion nobody can hear and another example of .01% distortion anyone can hear. Depends on the nature of the distortion.
That being said, I think there is some pretty good evidence that hearing little subtleties of sound is an ability that is some mixture of innate and learned. People who train as recording and mastering engineers traditionally go through years of training. I have also found that as people get experience mixing they get better a noticing such things.
Where you might be in that spectrum I have no idea, but I think given the opportunity to listen to a really good system or to compare systems at low-ish volume levels in the near field that you might be able to hear a lot more than you expect.
Unfortunately, you may never get a chance to find out unless you know someone with a good system, or you decide to diy your own. There are no more stereo stores where people can go listen to upscale systems.
THD is a terrible way to measure anything, particularly a dac. There is lot more to them that can affect sound quality than just simple stationary HD. I did take my 1st modded dac board to Richard Marsh's who has some measuring equipment. He said all the harmonics are below -120dB, most of the down at -130dB or lower. Of course, if using DSD for playback, noise is probably going to be higher than for PCM. We didn't have time to do more as we spent a lot of time investigating some odd spurs down at -130dB. They mostly went away when I put my finger on the clock. Don't know what was going on there. I'm not seeing them now when I look at harmonics for HD compensation adjustment. Thing about measuring here is I can do it now if the dac is the steel file server case, which shields the EMI/RFI around here. Although the calibration is not perfect on that, it looked looked like the harmonics were still down around where Richard measured them. Of course, there are a number of other tests that really ought to be done for a dac.
EDIT: Also, when I did HD compensation in the dac registers for H2 and H3, I could only reduce them maybe a couple of dB each. One, H2, required a tweak of 5 out +-32,000 and H3 was lowest with a setting of -6. That distortion was minimized with almost no compensation is consistent with the distortion being down about as low as it can get with one of these ES9038Q2M dacs. It should be too, I have done pretty near everything I know how to do to make it as low distortion as possible.
As far as how I judge as I go with mods, whether they are taking it in the right direction, the wrong direction, or I can't really tell, I do that mostly by quick (or slow) A/B comparisons with DAC-3. Of course, DAC-3 always sounds better and more accurate. More like real instruments and voices, as well as more detailed. However, that is in near field listening at a very specific volume level. Walk to the other side of the room out of the near field and turn up the volume a little and it can be much more difficult or impossible for me to tell a difference. That's mostly because they are both very good Sabre implementations (with DAC-3 clearly better up close).
As far as whether or not you could hear the differences yourself, Earl Geddes, a hearing researcher and speaker designer who hangs out at diyaudio sometimes says that he can show an example of .01% distortion nobody can hear and another example of .01% distortion anyone can hear. Depends on the nature of the distortion.
That being said, I think there is some pretty good evidence that hearing little subtleties of sound is an ability that is some mixture of innate and learned. People who train as recording and mastering engineers traditionally go through years of training. I have also found that as people get experience mixing they get better a noticing such things.
Where you might be in that spectrum I have no idea, but I think given the opportunity to listen to a really good system or to compare systems at low-ish volume levels in the near field that you might be able to hear a lot more than you expect.
Unfortunately, you may never get a chance to find out unless you know someone with a good system, or you decide to diy your own. There are no more stereo stores where people can go listen to upscale systems.
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In terms of pure measurement, can you quantify based on an order of magnitude improvement in THD based on your mods? For discussion purposes, if we use a starting point of .3 THD for the SMPcb ES9038Q2M stock board, do your mods progressively improve that to say, .03 or even further to say, .003? Is there a 10-fold level of improvement to be had? To be honest, I'm not sure I can even hear a difference between .03 and .003 THD!
i agree, the room acoustics could easily cancel that thd improvement.