OSHW audio design for critique - Page 1
Forum section: electronics / general

author: blueskull
author_rank: Unknown
timestamp: October 01, 2015, 05:55:09 am
content: !!!WARNING LARGE DESIGN!!! Project Plethora high performance audio DACHi all,There is my audio DAC design for review. This is only the digital receiver, interpolation, delta sigma modulation, power and output connector board.The actual thermometer DAC and low noise LDO daughter board hasn't been finished yet.This is only 1/4 of the entire design. The rest 3/4 are:a. DAC daughter board,b. DSP firmware,c. FPGA firmware,d. The most important part, the DAC ASIC. I now have a chance to do an affordable MPW run on CSMC 0.5um mixed signal process.Detailed documentation can be found in the attached zip file (7z format with zip extension name).+1.1, 1.2, 3.3V power plane and ground plane are left blank for better visibility.Thanks,BoAdded final gerber and pcb files. Check out here.

author: Dago
author_rank: Frequent Contributor
timestamp: October 01, 2015, 10:30:29 am
content: Tried to have a look but schematic seems to be unreadable.

author: Andy Watson
author_rank: Super Contributor
timestamp: October 01, 2015, 11:17:58 am
content: Quote from: blueskull on October 01, 2015, 10:58:32 amHmmm! Let's see if I have this right. You are providing a file in a format (7z) that would require me to jump through several hoops in order to undo it on a Linux platform. Then, if I jump through those hoops, the schematic is essentially unreadable to anybody who doesn't already have the insider-knowledge of its creator.

author: Monkeh
author_rank: Super Contributor
timestamp: October 01, 2015, 11:33:05 am
content: Quote from: Andy Watson on October 01, 2015, 11:17:58 amEr, it's just a 7z, there's not a lot of hoop jumping there.As far as reading it goes, however.. gah.

author: Monkeh
author_rank: Super Contributor
timestamp: October 01, 2015, 11:37:31 am
content: Quote from: blueskull on October 01, 2015, 11:36:17 am.. And that's the whole purpose of a schematic, to convey this information.Which yours fails to do.You may as well post in Chinese, because it's much the same thing.

author: Andy Watson
author_rank: Super Contributor
timestamp: October 01, 2015, 11:48:28 am
content: Quote from: Monkeh on October 01, 2015, 11:33:05 amIt is not a format that I can readily open. The limited research that I have put into opening these files is suggesting that I will have to cobbled-together some software to undo a format that is centred on M$ technology. May it's not much of a hoop if you already have that unzipper, but it is further than I am prepared to jump.

author: Monkeh
author_rank: Super Contributor
timestamp: October 01, 2015, 11:57:24 am
content: Quote from: Andy Watson on October 01, 2015, 11:48:28 am${PACKAGE_MANGLER_OF_CHOICE} p7zip7z x ${FILE}done.I am immensely puzzled where you get the idea it's in any way tied to Microsoft.

author: Monkeh
author_rank: Super Contributor
timestamp: October 01, 2015, 12:03:40 pm
content: Where you see a holy war, I am merely trying to help someone. Why, exactly, I'm not sure, as I've seen what lies within the archive.

author: singapol
author_rank: Frequent Contributor
timestamp: October 02, 2015, 05:18:47 am
content: The only difference you are trying to do is that I see in usb otg.gif is a box listed as "fuel gauge".Is this for car audio? I am sure there are similar chinese products that have this conceptmaybe cheaper and less complicated to save costs.It is amusing that you come here to ask for opinions about something like audio as you have pointed outlike cpu OSs.Talking about them is like religion and you want to avoid that.Still it's not strangeif you are an engineer asking in an engineering/hobbyist forum.The question most relavant to your success is who are your target users/customers.How much are theywilling to pay for your ground breaking product this being a"high performance audio".I like to point out a common assumption that engineers assume in audio that if it 's got sound it then passes the test and therefore ready to go to market after verifying the specifications.The thing engineers must come to a realisation that, does designing for test instruments that replace thehuman ear showing low distortion, low this and that etc. equate to what a human would find listenableor musical? Oh I'll bet you will say this is audiophools territory.What matters is the test results measured.Can test equipment replace the human ear and for that the ear is connected to the human via brain and other senses. Can test equipment really take all these into account?In the end you must ask yourself who you are designing for, test equipment or human beings.Engineers must sort this out if they are to make any significant progress towards audio as many derogatorily say it's only 20 - 20Khz. What's so difficult about it?As an aside, there are many ways or methods to tune a musical instrument for tonality but ultimately this instrument must harmonise with the other musical instruments to create an enjoyable musical experience.I wish you success all the same.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 02, 2015, 05:27:06 am
content: What latency does it get? I can't image a good (quality wise) upscaler having particularly good latency, but maybe it's still low enough even for gaming use.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 02, 2015, 05:43:51 am
content: 24ms sounds like a lot for gaming. Might be a good idea to add a "game mode" that switches in an upscaler with less latency at the cost of a little less quality. In comparison, most ordinary DACs have latency less than a millisecond. I'm also sure the software layers on the PC side introduce far less than the 240ms you seem to imply. 240ms would be enough to make audio useless in many games.Also, gamers at least used to frown on USB audio. Not sure if it's still relevant.

author: singapol
author_rank: Frequent Contributor
timestamp: October 02, 2015, 05:48:31 am
content: Quote from: blueskull on October 02, 2015, 05:27:36 amAh..."fuel gauge" is battery monitor.So it's a portable audio device which I said there are already similarchinese products already on the market.They are trying to copy the success of CHORD Electronics "HUGO" which I have listen to before it beat a diy quad dac (4X) machine.Impressive but not cheap. It uses fpga and dsp techniques which CHORD is well known for. You can read the design philoshopy of HUGO design at CHORD's website. I think you can get some idea of what the designer is aiming for.You have right mindset about human ear as the gold standard. Yes your dsp idea is in the right directionof which the designer of HUGO also think in similar fashion.For a fact HUGO use only 1 power supply for all circuits you have many. Is it good or your pproduct may bebigger than HUGO but if you can beat HUGO I got nothing to say.You have to have low noise power supply and dsp algorithms ( the secret). ( You are like man in front of tank at Tian An Men Square. )GOOD LUCK.

author: singapol
author_rank: Frequent Contributor
timestamp: October 02, 2015, 09:48:19 am
content: Quote from: blueskull on October 02, 2015, 06:01:28 amDear friend I think you are too idealistic about OSHW. With your talent you can do many things. I heard there are specialised companies in China that can reverse engineer any product and provide a prototype pcb in 24hrs.A bit far fetched?Judging from the size of your pcb I don't think it will be a threat to HUGO but who knows. But I think yourproject is the first to take on HUGO head on because you are using fpga and dsp method. The other "clones" are just using off the shelf dac and usb stuff. None of the high resolution playback thing.That said I think you should market it yourself if it works. You deserve every yuan you make.I have met the founder of CHORD Electronics briefly when he travels to asia to visit his asian distributorsregularly. He is an Englishman and engineer himself. I think he started small like everyone else and eventually grew. You also need to keep an eye on current trends in the audio field to survive. If you want to be successful work for yourself not others be your own boss.

author: singapol
author_rank: Frequent Contributor
timestamp: October 02, 2015, 04:26:46 pm
content: Can I say all the circuits you described, power, fpga,dsp, usb and dac are on this one single pcb? What about the connectors, power, usb,signal output like RCAs, etc? What is more surprising to me is what capsare you using for signal analog coupling? All I see are smt footprints and no throughhole components.

author: singapol
author_rank: Frequent Contributor
timestamp: October 02, 2015, 04:45:15 pm
content: Quote from: blueskull on October 02, 2015, 04:32:58 pmIs the dac a off the shelf chip or implemented in fpga? Experience has shown mlcc caps for signal willnot sound good at least to the ears trust me, despite what instrumentation suggest.

author: singapol
author_rank: Frequent Contributor
timestamp: October 02, 2015, 05:11:32 pm
content: Quote from: blueskull on October 02, 2015, 04:57:27 pmPlease use film caps polypropylene (mkp type like WIMA red ) at the very least if you want serious audiophiles to be interested.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 03, 2015, 04:48:41 am
content: Be sure to validate it on a USB 3.0 port, even if the unit itself only supports USB 2.0. There's a strange compatibility issue with some USB 3.0 ports. I know the common NEC/Renesas controllers got some firmware updates to fix some issues, not sure if they might be related.http://createdigitalmusic.com/2012/06/usb-3-0-backwards-compatible-in-theory-but-some-audio-drivers-arent-cooperating/

author: singapol
author_rank: Frequent Contributor
timestamp: October 03, 2015, 06:47:41 am
content: Is your asic dac same as Hugo's 32 bit? Want to be sure we compare apples with apples, looking forwardto your giant killer.

author: singapol
author_rank: Frequent Contributor
timestamp: October 03, 2015, 07:19:03 am
content: Quote from: blueskull on October 03, 2015, 06:49:01 amOK current output sigma delta dac...so I/V convertor is external via opamp which gives flexibility of opamp choice for modders.

author: singapol
author_rank: Frequent Contributor
timestamp: October 03, 2015, 07:28:33 am
content: Quote from: blueskull on October 03, 2015, 06:49:01 amFantastic! You are the man.