DIY HiRez Minimum Phase DAC

HAL · « **on:** 7 Jun 2016, 08:13 pm »

Working on a DIY HiRez minimum phase DAC based on the AKM AK4490EQ DAC and Amanero asynchronous USB to I2S Bus interface.

Total parts cost is around $170. Should do DXD and DSD256 as the max rates.

I prefer minimum phase DAC's to any linear phase filtered DAC chip that is in use. Another good one is the Wolfson Micro (now Cirrus Logic) WM874x series DAC. There are a few good research papers that discuss the psychoacoustic reasons for this preference, and my listening agrees with the research.

Will take pictures and post some results using it with the HAL MS-3 Music Server setup. This will be a desktop rig with my iFi iCan headphone system and HiFiMan HE500 planars and Etymotic Research ER-4S in ear phones.

HAL · « **Reply #1 on:** 11 Jun 2016, 10:11 am »

Here is the beginning of the DIY DAC.

The AK4490EQ board from Ebay, Amanero USB to I2S Bus board, dual output 9VAC toroid and 25.2VAC CT E-I core power transformers. Sent an email to the company to see which filter type is selected on the board, since it is hard wired.

HAL · « **Reply #2 on:** 12 Jun 2016, 07:45 pm »

Will be testing the DIY AK4490EQ DAC with the Grand Piano recording I did last evening at 24bit/192KHz. The WAV files will be the recording.

Odal3 · « **Reply #3 on:** 12 Jun 2016, 10:19 pm »

What's the difference between a minimum phase dac and a linear phase filtered dac?

HAL · « **Reply #4 on:** 12 Jun 2016, 11:05 pm »

A linear phase filter is one that has preringing and post ringing in the response. It is non-causal meaning things occur before an input happens. Nothing in nature does this, only digital.

A minimum phase filter has no preringing. Works just as any normal passive filter would and nothing to confuse the ear-brain system in the psychoacoustic realm.

A very good paper was written about this about 10 years ago at a college in the UK. Follow on research has lead to the Meridian Audio MQA system.

*Scotty* · « **Reply #5 on:** 13 Jun 2016, 12:10 am »

Here are some graphic examples of the two filter types courtesy of the Stereophile review of the Auralic Vega
Linear Phase filter below

Minimum Phase filter below

Scotty

HAL · « **Reply #6 on:** 13 Jun 2016, 12:43 am »

Scotty,
Excellent examples.

Odal3 · « **Reply #7 on:** 13 Jun 2016, 02:49 am »

Ah - now I know what you're talking about. Thanks for explaining.

HAL · « **Reply #8 on:** 15 Jun 2016, 11:57 pm »

Looking at the parts layout on the breadboard before drilling the mounting holes for the boards and transformers.

shadowlight · « **Reply #9 on:** 16 Jun 2016, 02:37 pm »

Rich,

Are you planning to add a dedicated power supply for the Amanero?

HAL · « **Reply #10 on:** 16 Jun 2016, 02:58 pm »

No plan to add a dedicated power supply for the Amanero.

I have an iFi iPower iUSB to use with it and with my iCans HPA, so not needed in my case.

HAL · « **Reply #11 on:** 29 Jun 2016, 12:29 am »

Back from travel and the AK4490EQ DAC is running and making HiRez music.

Setup is my MS-2 to the Amanero USB to I2S Bus board directly connected to the AK4490EQ board.

Transformers are connected directly to the PC board as in the picture with a fuse on the AC line.

Will get it all mounted on the PC Board and let the DCAudioDIY guys try it at CAF2016 with their PC's. Will be interesting to get feedback for a very simple DAC project.

mlundy57 · « **Reply #12 on:** 30 Jun 2016, 12:56 am »

Rich,

Interesting. Did you have to populate the DAC board or did it come fully populated?

How does this compare with the 32/387 DODD Amanero / Wolfson DAC you repaired for me awhile Back, other than the DODD only does DSD 64?

Mike

HAL · « **Reply #13 on:** 30 Jun 2016, 01:15 am »

Mike,
I just got it all working and still getting things setup.

The Amanero board is the same board I have in my Dodd DAC with the Wolfson DAC system. I think it was the same in yours.

The DAC board is fully built with surface mount and through hole components. Has very good Linear Tech LT series regulators for the analog stage, and separate regulators for the DAC chip. Similar to the Wolfson board's power supplies. The output opamp is an AD827 which can be replaced with a favorite dual high speed low offset opamp.

Will be trying it more with the headphone setup, once I make it a bit more stable to handle. Not very safe AC electrically at the moment. Need to attach things to the board first.

More once I know.

HAL · « **Reply #14 on:** 30 Jun 2016, 11:03 am »

Have my Netbook setup with Windows 10 Home 64bit OS, Foobar2000 and the Amanero USB driver.

Once I get the DAC built up, will use that system as the test with the iFi iUSB and iCan headphone amp running my HiFiMan HE500's. Will see how it goes.

If it sounds good, will take it to CAF2016 for the DCAudioDIY room 218 for folks to listen to. It will have some of the Reference Recordings HRx WAV files loaded for 24bit/176.4KHz HiRez replay. They will also have a Linux based PC with a DAC for listening and a CD transport with S/PDIF input DAC.

Since the ASUS Netbook has extra USB ports, a USB flashdrive with WAV of FLAC files will work for playback. I will set it up to be watching for external USB drives.

One specific track with be from the new Reference Recordings Saint-Seans Symphony #3, last movement with the pipe organ. I heard they are bringing subs.

mlundy57 · « **Reply #15 on:** 30 Jun 2016, 03:33 pm »

Rich,

Thanks

Have fun

Mike

HAL · « **Reply #16 on:** 30 Jun 2016, 04:04 pm »

Also looking at putting the latest build of Windows 10 IoT on the Raspberry Pi3 to see if Foobar2000 mobile can be compiled for the system. If so, that would make a very interesting alternative to the Linux OS for the RPi3.

The development tools are similar for RPi3 and Foobar2000. Will see what happens. The Amanero uses a ASIO USB driver, so that might be the sticking point.

If that works, would be a full music server and HiRez DAC with a front end on the RPi3 for a very reasonable cost. I am not a fan of headless music servers since they are totally noiseless and can sit by my seat.

This would probably not run MathAudio Room EQ, but for a simple system would be very cool.

maty · « **Reply #17 on:** 2 Jul 2016, 06:52 am »

I think you are interested

MUSINGS: Digital Interpolation Filters and Ringing (plus other Nyquist discussions and "proof" of High-Resolution Audio audibility)

-> http://archimago.blogspot.com/2016/07/musings-digital-interpolation-filters.html

2015

INTERNET BLIND TEST: Linear vs. Minimum Phase Upsampling Filters

-> https://archimago.blogspot.com/2015/04/internet-blind-test-linear-vs-minimum.html

The Linear vs. Minimum Phase Upsampling Filters Test [Part I]: RESULTS

-> http://archimago.blogspot.com/2015/07/the-linear-vs-minimum-phase-upsampling.html

HAL · « **Reply #18 on:** 2 Jul 2016, 11:35 am »

Since the SINC function that is discussed is an infinite function in the time domain in both directions, all linear phase filters use an approximation of it, not the full function. The minimum phase approach is another approximation that does not use a non-causal filter to do reconstruction. Since these minimum phase filters have minimized the post ringing to minimize time smear, but still provide enough filtering to get rid of the aliasing components in the digital waveform before output it is also a good approximation.

After listening to DAC's for over 30 years. I have a preference for minimum phase filter sound. It has held up with multiple comparisons in my listening room with acoustical instrument recordings that I am very familiar with. Agree with the first discussion site, just go try it and have a listen.

I will stick with minimum phase filters and other folks can have their linear phase ones. To each their own. The DIY AK4490EQ DAC is on the breadboard and getting setup for CAF2016. Will be doing more checks up to the show.

HAL · « **Reply #19 on:** 2 Jul 2016, 06:35 pm »

The DIY music server system for CAF2016, room 218. ASUS Netbook PC running Foobar2000 and DIY AK4490EQ HiRez DAC. Loaded Reiner conducting the Brahms 3rd and 4th Symphony in DXD 32bit/352.8KHz and Reference Recordings Exotic Dances HRx files in 24bit/176.4KHz format on the machine for some music.

The Netbook has spare USB ports for external file replay if folks bring USB hard or flashdrives with music.

I know the DCAudioDIY folks have a Linux machine and DAC setup for their music library as well.

Hope folks can go out to give a listen to systems built by music lovers for home reproduction.