Author Topic: OSHW audio design for critique  (Read 11803 times)

0 Members and 1 Guest are viewing this topic.

Offline singapol

  • Frequent Contributor
  • **
  • Posts: 420
  • Country: sg
Re: OSHW audio design for critique
« Reply #25 on: October 02, 2015, 09:48:19 am »

In the OSHW world there are no secrets. Maybe I will get profit by providing "device cloning" service, so that I can create customized "profiles" for any samples the customer provides. Or I can make money by sublicensing companies to do non-open source derived works.

DSP code will be USB stack, cubic, polyphase FIR and FFT filters that the industry used for tens of years. There will be some black magic in reducing calculating complexity, but anyway I will publish it somewhere such as IEEE some time, so there are really no magic.

For the real interesting part, how to eliminate non-linear distortion, I referred something from ES9018's patent, but took a huge detour, so it won't violate any patents. These parts (SDM, DEM and calibration) are done in FPGA. All FPGA diagrams, HDL code and test benches will be open source.

There are nothing too excited in the ASIC, and if you want, you can build it with a FPGA and a shitload of logic gates and resistors with a couple of transistors. The only reason I decided not to open source the ASIC design is because the process provider doesn't allow me to do this.

The final product is WAY smaller than HUGO. The finished assembly is estimated to be smaller than 25mm*60mm*8mm.

Dear 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. :o 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 your
project 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. :D

I have met the founder of CHORD Electronics briefly when he travels to asia to visit his asian distributors
regularly. 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. :-+
 

Online blueskull

  • Supporter
  • ****
  • Posts: 12885
  • Country: cn
  • Power Electronics Guy
Re: OSHW audio design for critique
« Reply #26 on: October 02, 2015, 09:56:44 am »
Thank you for your encouragement. Doing engineering and challenging limits is my hobby, and surely making money from them is cool. But I don't do this design as a living. My living skill is power system and power electronics engineering, and my degree is a MS-electric power system engineering, which is also a msee degree.

Talking abt pcb reverse engineering, anyway they will reverse it. Instead of letting the others making crude clones that ruin my reputation, why not open it up and sell proprietary asics and services?
 

Offline singapol

  • Frequent Contributor
  • **
  • Posts: 420
  • Country: sg
Re: OSHW audio design for critique
« Reply #27 on: October 02, 2015, 04:26:46 pm »
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 caps
are you using for signal analog coupling? All I see are smt footprints and no throughhole components.
 

Online blueskull

  • Supporter
  • ****
  • Posts: 12885
  • Country: cn
  • Power Electronics Guy
Re: OSHW audio design for critique
« Reply #28 on: October 02, 2015, 04:32:58 pm »
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 caps
are you using for signal analog coupling? All I see are smt footprints and no throughhole components.

Analog part will be on a daughter card. For the caps, mlcc will be used. Don't be surprised, with careful design mlcc can be used. Of course, only np0 will be used in signal path, and they will only work as very frequency lpf. Otherwise it makes no sense to take so much effort to do 128-256x oversampling. Connectors will be only micro usb and two 3.5mm jacks.
 

Offline singapol

  • Frequent Contributor
  • **
  • Posts: 420
  • Country: sg
Re: OSHW audio design for critique
« Reply #29 on: October 02, 2015, 04:45:15 pm »
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 caps
are you using for signal analog coupling? All I see are smt footprints and no throughhole components.

Analog part will be on a daughter card. For the caps, mlcc will be used. Don't be surprised, with careful design mlcc can be used. Of course, only np0 will be used in signal path, and they will only work as very frequency lpf. Otherwise it makes no sense to take so much effort to do 128-256x oversampling. Connectors will be only micro usb and two 3.5mm jacks.

Is the dac a off the shelf chip or implemented in fpga? Experience has shown mlcc caps for signal will
not sound good at least to the ears trust me, despite what instrumentation suggest. :-\
 

Online blueskull

  • Supporter
  • ****
  • Posts: 12885
  • Country: cn
  • Power Electronics Guy
Re: OSHW audio design for critique
« Reply #30 on: October 02, 2015, 04:57:27 pm »
The dac will be an asic. I got a deal from csmc and they can offer me 0.5um 2p3m mixed signal process for $2500.

For the caps, the dac board has enough space to let me implement film caps based filter, so if needed I can squeeze some space from other modules.
 

Offline singapol

  • Frequent Contributor
  • **
  • Posts: 420
  • Country: sg
Re: OSHW audio design for critique
« Reply #31 on: October 02, 2015, 05:11:32 pm »
The dac will be an asic. I got a deal from csmc and they can offer me 0.5um 2p3m mixed signal process for $2500.

For the caps, the dac board has enough space to let me implement film caps based filter, so if needed I can squeeze some space from other modules.

Please use film caps polypropylene (mkp type like WIMA red ) at the very least if you want serious audiophiles to be interested.  ;D
 

Offline NiHaoMike

  • Super Contributor
  • ***
  • Posts: 5833
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: OSHW audio design for critique
« Reply #32 on: October 03, 2015, 04:48:41 am »
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/
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 

Online blueskull

  • Supporter
  • ****
  • Posts: 12885
  • Country: cn
  • Power Electronics Guy
Re: OSHW audio design for critique
« Reply #33 on: October 03, 2015, 04:57:33 am »
Will do. Will starr fw oding soon.
 

Offline singapol

  • Frequent Contributor
  • **
  • Posts: 420
  • Country: sg
Re: OSHW audio design for critique
« Reply #34 on: October 03, 2015, 06:47:41 am »
Is your asic dac same as Hugo's 32 bit? Want to be sure we compare apples with apples, looking forward
to your giant killer.  :clap:
 

Online blueskull

  • Supporter
  • ****
  • Posts: 12885
  • Country: cn
  • Power Electronics Guy
Re: OSHW audio design for critique
« Reply #35 on: October 03, 2015, 06:49:01 am »
Is your asic dac same as Hugo's 32 bit? Want to be sure we compare apples with apples, looking forward
to your giant killer.  :clap:

4 bit thermometer dac. Sigma delta modulation is done on fpga.
 

Offline singapol

  • Frequent Contributor
  • **
  • Posts: 420
  • Country: sg
Re: OSHW audio design for critique
« Reply #36 on: October 03, 2015, 07:19:03 am »
Is your asic dac same as Hugo's 32 bit? Want to be sure we compare apples with apples, looking forward
to your giant killer.  :clap:

4 bit thermometer dac. Sigma delta modulation is done on fpga.

OK current output sigma delta dac...so I/V convertor is external via opamp which gives flexibility of opamp choice for modders.  :-+
 

Online blueskull

  • Supporter
  • ****
  • Posts: 12885
  • Country: cn
  • Power Electronics Guy
Re: OSHW audio design for critique
« Reply #37 on: October 03, 2015, 07:21:02 am »
Is your asic dac same as Hugo's 32 bit? Want to be sure we compare apples with apples, looking forward
to your giant killer.  :clap:

4 bit thermometer dac. Sigma delta modulation is done on fpga.

OK current output sigma delta dac...so I/V convertor is external via opamp which gives flexibility of opamp choice for modders.  :-+

External iv, but with current mirror, so slower speed of opamp won't create trouble. Also, there are measures to tackle down inter symbol interference.
 

Offline singapol

  • Frequent Contributor
  • **
  • Posts: 420
  • Country: sg
Re: OSHW audio design for critique
« Reply #38 on: October 03, 2015, 07:28:33 am »



External iv, but with current mirror, so slower speed of opamp won't create trouble. Also, there are measures to tackle down inter symbol interference.

Fantastic! You are the man. :D
 

Online blueskull

  • Supporter
  • ****
  • Posts: 12885
  • Country: cn
  • Power Electronics Guy
Re: OSHW audio design for critique
« Reply #39 on: October 03, 2015, 02:52:31 pm »
New bug found. I found this bug minutes before submitting the design to OSHPark. The LVDS input from isolation transformer to FPGA was not properly biased. iCE40HX FPGA doesn't have internal LVDS biasing on pins. Using my logic analyzer and pattern generator can I observe severe glitch on my HX8K dev board if a LVDS input pair was not properly biased.
 

Online blueskull

  • Supporter
  • ****
  • Posts: 12885
  • Country: cn
  • Power Electronics Guy
Re: OSHW audio design for critique
« Reply #40 on: October 06, 2015, 03:32:57 pm »
Updated design, what's new:
1. Removed +2.5V power rail. I tested on my breakout board and I can see LVDS receiver works just fine on +3.3V. So I removed +2.5V, and this gives me nice sexy +3.3V power plane for better distributed decoupling.
2. Power traces re arranged to get uncut power rails for all power supplies under DSP and FPGA.
3. LVDS traces on primary side rerouted, parts rearranged to get a perfect match.
4. LVDS receiver biased with +1.2V, as well as a capacitor of course.
5. Fine adjusted ground planes for different domains.

There is an existing bug, which is over matched differential pair length in secondary side. This will be corrected in the next revision of the design.
This version's gerber files are sent to OSH Park and OSH Stencil for prototyping.

Attached is the latest design database.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf