MDAC First Listen (part 00110101)

[kennyh]

Any plans in the distant future for maybe a really trick DAC board for the RPI?

I was converted to RPI recently by lads on here and just with a standard IQAUDIO card the sound is sensational and I'm amazed in how it performs. Performance,stability and all round practicality make it a sure fire winner for years to come with millions of end users both hi end owners, and casual listeners.

It would sell in its thousands once word got out. Just a thought.

The forums are rife with people searching for the next new quality card to come out.

 

[EIffel]

Well, the MDAC2 may be seen as a 'really trick DAC board/case/PSU for the RPI', assuming it gets support for some of the common software distribution (PiCore, etc.)

Clearly not in the same league as the Pi-Hat boards, but providing the same functionality in effect (provided one uses a CM3 rather than a Pi3 board, which in the end is a minor 'detail').

 

[Rune]

Well, the MDAC2 may be seen as a 'really trick DAC board/case/PSU for the RPI', assuming it gets support for some of the common software distribution (PiCore, etc.)

Clearly not in the same league as the Pi-Hat boards, but providing the same functionality in effect (provided one uses a CM3 rather than a Pi3 board, which in the end is a minor 'detail').

You actually do not need to spend time on different linux distributions.
No need for picore player!
I am sure the build jirij is makin will have squeezelite.

 

[JohnW]

Any plans in the distant future for maybe a really trick DAC board for the RPI?

I was converted to RPI recently by lads on here and just with a standard IQAUDIO card the sound is sensational and I'm amazed in how it performs. Performance,stability and all round practicality make it a sure fire winner for years to come with millions of end users both hi end owners, and casual listeners.

It would sell in its thousands once word got out. Just a thought.

The forums are rife with people searching for the next new quality card to come out.

Well you will not get much better then the MDAC2 as a "DAC" for the RPI. The CM3 module is basically the RPI3 but without WiFi module.

 

[JohnW]

Thanks Fusion5 and John for the info re. RPi. Two questions:

1. If an RPi is NOT installed in MDAC2, do we have access to the second USB input on the rear panel?

The secondary USB is an internal BUS on the CM3 daughter PCB and cannot be used as a second USB input when the CM3 is not fitted.

Also, there is an HDMI connector. Can that be used for audio input, or is it for monitor display output only?

Its the HDMI output of the CM3 (RPI3) I'm not sure if this supports audio, but its nothing to do with the MDAC2 "Audio" path.

2. What would be the comparative advantages to having an RPi inside the MDAC2 case or an external one, if any?

Having the CM3 board internal allows "Jitter less" audio interface via internal Async USB (freeing the MDAC2's primary USB port) and basic Detox locked to the audio clocks.

We are considering a later MDAC2 front panel update with Colour display driven by the CM3 module.

Disadvantages:-

Extra internal RF within the MDAC2.

 

[highfi]

Having the CM3 board internal allows "Jitter less" audio interface via internal Async USB (freeing the MDAC2's primary USB port) and basic Detox locked to the audio clocks.

So you feel USB to be superior to i2s in this case?

We are considering a later MDAC2 front panel update with Colour display driven by the CM3 module

Cool!

 

[kennyh]

Well you will not get much better then the MDAC2 as a "DAC" for the RPI. The CM3 module is basically the RPI3 but without WiFi module.

What I was referring to John was a board designed to actually fit on to the RPI and use the tiny ciggy packet sized box as an all in one, ie, phono or if you prefer XLR out to amp and that's that, no messing with USB's or anything else.

As I say the market has a few very good boards available now that do giant killing jobs against far pricier kit, with people always looking for the next arrival to try, especially if it was from an already recognised hifi outfit.

Massive market and surely a lot less work than a big box full of other toys people like myself have already got.

 

[Nick1881]

Nick,

For the clock, you will need a 500MHz + Scope?

In instances where the DAC operation is "unstable" with USB then the clock will have high cycle to cycle jitter - so the edges will be "wide" rather then nice "thin" edges.

Bad Clock (Crystal)

https://dl.dropboxusercontent.com/u/86116171/MDAC Jitter.jpg

Good Clock:-

https://dl.dropboxusercontent.com/u/86116171/MDAC Replacement clock.JPG

I dont have any more replacement crystals here so you will have to order one from IAG UK - it should cost no more then GBP10 with postage...

Ah, my work scope is only 100Mhz. I'll just buy the crystal, works out cheaper than a 500Mhz scope

Could you tell me what the crystal is please? Maybe I could source it from RS or somewhere.

 

[JohnW]

Ah, my work scope is only 100Mhz. I'll just buy the crystal, works out cheaper than a 500Mhz scope

Could you tell me what the crystal is please? Maybe I could source it from RS or somewhere.

Nick,

Sadly its a custom cut for the MDAC so its not available anywhere else - you will have to order from IAG UK.

84MHz - for MDAC

 

[JohnW]

What I was referring to John was a board designed to actually fit on to the RPI and use the tiny ciggy packet sized box as an all in one, ie, phono or if you prefer XLR out to amp and that's that, no messing with USB's or anything else.

As I say the market has a few very good boards available now that do giant killing jobs against far pricier kit, with people always looking for the next arrival to try, especially if it was from an already recognised hifi outfit.

Massive market and surely a lot less work than a big box full of other toys people like myself have already got.

We design such a DAC for the H3 PCB, but sonically its really a compromise. OK for a GBP200 DAC, but not in MDAC2 league...

https://dl.dropboxusercontent.com/u/86116171/Streamer Dev DAC1.jpg

https://dl.dropboxusercontent.com/u/86116171/Streamer Dev DAC2.jpg

https://dl.dropboxusercontent.com/u/86116171/Streamer Dev DAC3.jpg

https://dl.dropboxusercontent.com/u/86116171/Streamer Dev DAC4.jpg

 

[kennyh]

We design such a DAC for the H3 PCB, but sonically its really a compromise. OK for a GBP200 DAC, but not in MDAC2 league...

https://dl.dropboxusercontent.com/u/86116171/Streamer Dev DAC1.jpg

https://dl.dropboxusercontent.com/u/86116171/Streamer Dev DAC2.jpg

https://dl.dropboxusercontent.com/u/86116171/Streamer Dev DAC3.jpg

https://dl.dropboxusercontent.com/u/86116171/Streamer Dev DAC4.jpg

Interesting John and many thanks,that looks very neat indeed, what dac chip is it? Would this fit directly on to an RPI3 as say the Audiophonics/Iqaudio card does?

Is it available from you directly or from other appointed vendors?, and finally not having heard an MDAC2 personally, how in your opinion does it compare to a healthy/recapped standard Mdac?

Again thank you.

 

[JohnW]

So you feel USB to be superior to i2s

I2S is used in most DAC designs as an internal Audio datapath - the trouble with RPi3 (also with the H3 & Beaglebone boards) I2S interface is:-

1. Its hard to enable "Master Mode" where the DAC is clock Master - you need custom drivers and with devices like the H3 its not well documented.

2. Hardware Limited to 192KHz

Using the USB allows an Async connection where the DAC's clock is used for "Jitter free" Audio Data - and USB Audio drivers are "native" in most Linux builds.

768KHz and higher is possible via the USB interface.

 

[JohnW]

Interesting John and many thanks,that looks very neat indeed, what dac chip is it? Would this fit directly on to an RPI3 as say the Audiphonics/Iqaudio card does?

Is it available from you directly or from other appointed vendors?, and finally not having heard an MDAC2 personally, how in your opinion does it compare to a healthy/recapped standard Mdac?

Again thank you.

The PCB was a development PCB for the H3 PCB, in the end it was not possible to enable Master I2S mode so it was a total waste of time and funds.

MDAC2 will be in a completely different league to MDAC - pretty much a "Reference" performance DAC - I've been working on the "genesis" of the design since 2011!

 

[kennyh]

Shame, I would have liked to have tried one. The card I have now is pretty damn incredible for its meagre price tag.

Thanks again for the info., appreciated.

 

[miero]

JohnW: I just wonder why have you not used a BeagleBone Black for this embedded player. It accepts Master Clock and it has 4 I2S outputs, which could be used for native DSD playback (4 channels). Officialy it supports only 192kHz, but it works well with 384kHz in stereo mode (but no 768kHz).

The USB way is much more difficult than that.

 

[jirij]

The PCB was a development PCB for the H3 PCB, in the end it was not possible to enable Master I2S mode so it was a total waste of time and funds.

I still have the replacement H3 board I bought and even with i2s master being the H3, it could still sound pretty decent (ie. a car system?), I can provide an OS image with appropriate kernel if you want (and I still owe you the H3 board).

I still have the shell script to program the board via i2c.

edit: Actually, thinking about it some more, it would need some work to get into a workable state as the sample rate switching, etc., would have to be done externally via i2c, so I'd probably need to software-upsample everything to a fixed rate before sending it to the dac. Also volume control would have to be software (unless the user wants to send raw i2c commands to the dac to change the volume).

 

[kennyh]

So the board never reached production then? A huge market may have appreciated it if available and sounding good.. You'd have to erase the "car stereo" bit though

 

[JohnW]

JohnW: I just wonder why have you not used a BeagleBone Black for this embedded player. It accepts Master Clock and it has 4 I2S outputs, which could be used for native DSD playback (4 channels). Officialy it supports only 192kHz, but it works well with 384kHz in stereo mode (but no 768kHz).

The USB way is much more difficult than that.

Well USB is far easier for us (and Audio streaming is supported by almost all Linux distributions) - in the end the Beagebone proved REALLY underpowered.

Agreed, we also tested to 384KHz ok, but again its really underpowered and "obscure" (not well supported) where the CM3 (RPi3) avoids all these issues.

 

[JohnW]

I still have the replacement H3 board I bought and even with i2s master being the H3, it could still sound pretty decent (ie. a car system?), I can provide an OS image with appropriate kernel if you want (and I still owe you the H3 board).

I still have the shell script to program the board via i2c.

edit: Actually, thinking about it some more, it would need some work to get into a workable state as the sample rate switching, etc., would have to be done externally via i2c, so I'd probably need to software-upsample everything to a fixed rate before sending it to the dac. Also volume control would have to be software (unless the user wants to send raw i2c commands to the dac to change the volume).

JiriJ,

The last info I had from you was that Master mode did not look promising? did you ever get it working?

USB "pathway" with HID solves so many software issues.

 

[jirij]

JiriJ,

The last info I had from you was that Master mode did not look promising? did you ever get it working?

USB "pathway" with HID solves so many software issues.

Well there's always a master and a slave, we never managed to get ess=master + h3=slave working, but ess=slave + h3=master worked (as far as Jarek told me). The issue is that any control (switching clocks, sample rates, volume, filters, etc.) needed to be done via i2c manually, not via any "standard" means (ALSA mixer interface) that audio players would understand.