Network Renderer/DAC

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Ray P
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Network Renderer/DAC

Post by Ray P » Sun Feb 01, 2015 10:32 am

Image

Image

This is my 'new arrival', a network renderer/DAC based around an Acko SO3 reclocker board. I say based around because the Acko SO3, which has dual 90/98MHz clocks, is used to run the whole 'audio chain' synchronously.

The network renderer module is a BeagleBone Black (BBB) running the miero Botic Linux distribution. The BBB's onboard clock is disabled and clocking is provided by the Acko SO3, with clock selection according to the incoming data's sampling rate so there is no resampling (the BBB only has a single low quality clock so any 44.1KHz data would be resampled to 48KHz)

i2s from the BBB is passed to the Acko SO3 via onboard isolators where it is reclocked before onward transmission to my Twisted Pear Buffalo IIIse DAC. The DAC's onboard clock is disabled and clocking is provided by the Acko SO3 via 'turbo mode' connection.

Output from the DAC goes to a Twisted Pear Legato I/V module. Volume control is lossless digital, a function of the Sabre 9018 DAC chip used in the Buffalo IIIse

Most of the power supplies are shunt regulators by Salas (courtesy of DIY Audio group buys), a Reflektor-D for the AckoSO3, another for the Buff IIIse and a pair of BIBs for the Legato. A small LM317 linear regulator powers the BBB.

The front panel is American walnut.

I've so far had a good listen with headphones and first impressions are very positive, dynamic but with no edge and amazing detail and the noise floor must be very low as the background is inky black. It can only get better as it burns in. I've listened to 16bit/44.1Khz and 24bit/48, 96 and 192KHz recordings (all FLAC) with no glitches whatsoever.

Later today I plan to plug it into the main system for a listen.

Here are some links to the key components;

Acko SO3: https://sites.google.com/site/ackodac/home (a little way down on the right)

miero's Botic distribution: http://bbb.ieero.com/

Acko is working on a daughter board for the Beaglebone that will enable auto-switching between PCM and DSD.

I've overlain miero's distribution with a UPnP/DLNA controller (upnpdcli) so the renderer is controlled from a tablet using BubbleUPnP. I know there are some users of squeezebox solutions and I know that others have overlain miero's software with squeezelite.

Ray

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Post by Andrew » Sun Feb 01, 2015 11:23 am

Very impressive Ray.
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Paul Barker
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Post by Paul Barker » Sun Feb 01, 2015 1:31 pm

Just a quick question. Can the SO3 put out spdif or is it's output just i2s?
I can do it right or I can do it now, but I can't do it right now.

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Post by Ray P » Sun Feb 01, 2015 1:59 pm

Paul Barker wrote:Just a quick question. Can the SO3 put out spdif or is it's output just i2s?
Just i2s Paul.

What are you trying to achieve?

Ray

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Post by Paul Barker » Sun Feb 01, 2015 7:35 pm

Ray P wrote:
Just i2s Paul.

What are you trying to achieve?

Ray
I was wandering if it would go into my Beresford DAC but now I've seen the price of it I'll just stick with the vinyl. It's all I use for serious listening again. Have so little time for listening I do it best way I can.

Not saying there is anything badly wrong about digital, just there is plenty right about vinyl.
I can do it right or I can do it now, but I can't do it right now.

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Post by izzy wizzy » Sun Feb 01, 2015 8:28 pm

That looks vey nicely put together Ray. Particularly like the front panel.

cheers,

Stephen

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Post by IDM » Mon Feb 02, 2015 8:57 pm

Hi Ray,

That's a fantastic looking player. I am interested to know what the advantages of the Beaglebone black are over other Linux boards such as the Pi? Also have you ever tried the system without the reclocker, do you know how much contribution the board makes to the sonics?

I will upload some pics of my efforts over the next few days.

Cheers
Ian

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Post by Ray P » Tue Feb 03, 2015 8:19 pm

Thanks Ian.
IDM wrote: I am interested to know what the advantages of the Beaglebone black are over other Linux boards such as the Pi?
There's some useful information here,

https://hifiduino.wordpress.com/2014/11 ... tal-audio/

part way down is a comparison table of RPi and BBB functions. I moved to the BBB, having tried RPi devices, because it can be clocked properly from an external source, and because of the excellent Linux distribution put together by miero. The only disadvantage I can see for the BBB is it's susceptibility to damage from an uncontrolled power down, which is why I have a switch on my new renderer to shutdown the BBB before turning the power to the box off. I believe some people were trying to feed an external clock signal to a RPi but don't know where they got with it.
IDM wrote: Also have you ever tried the system without the reclocker, do you know how much contribution the board makes to the sonics?
No I haven't tried the system without the SO3 board but from the accounts of others it is not trivial. The SO3 isn't just about reclocking the i2s data, remember it is also supply clocking to the BBB (at frequencies that preserve native sample rates of the incoming data), it isolates the upstream BBB components from the fifo and it is also supplying clocking to the DAC chip. It's a potent little board. The SO3 could be used with a RPi and some improvements would be gained from the fifo reclocker, you would just have to feed the data from the RPi into the isolators 'as is'.

Incidentally, Acko is working on a cape for the BBB that will feature a small battery backup (to cleanly shutdown the BBB in the event of it losing normal power) and automatic switching to pass either DSD or PCM (i2s) data to the SO3 via the same wires. Twisted Pear are working on boards with similar reclocking etc. but they are still in development.

Maybe we should start some threads here to document the various options available for building a network renderer/dac for those less familiar with the concepts?

Ray

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Post by solarflight » Thu Feb 26, 2015 9:58 am

Hello, my first post on this forum. I came across this topic and it piked my interest.

It would be great to have some more insight in the various options that are available for building a network renderer/dac. I currently use a Raspberry with an ifi idsd micro.

I'm familiar with software installation but I completely lack the knowledge of electronics and assembly.

Some questions I have for example. Is it possible to attach an external dac with i2s to the beaglebone network renderer? Are there inputs for the dac so a disc player can be hooked up? Can you swap dac boards if you don't like the sound of one?

Anyway, it is a very nice network renderer and dac you have. I'm very curious how it sounds :-)

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Post by Ray P » Wed Apr 01, 2015 8:22 pm

solarflight wrote:Hello, my first post on this forum. I came across this topic and it piked my interest.

It would be great to have some more insight in the various options that are available for building a network renderer/dac. I currently use a Raspberry with an ifi idsd micro.

I'm familiar with software installation but I completely lack the knowledge of electronics and assembly.

Some questions I have for example. Is it possible to attach an external dac with i2s to the beaglebone network renderer? Are there inputs for the dac so a disc player can be hooked up? Can you swap dac boards if you don't like the sound of one?

Anyway, it is a very nice network renderer and dac you have. I'm very curious how it sounds :-)
Listening at the moment and the sound is amazingly good.

I posted a link with info on the comparison between the Beaglebone and RPi a few posts up.

To answer your specific questions;

Is it possible to attach an external dac with i2s to the beaglebone network renderer?

Yes that is possible, however, you need to consider that I2S connections need to be kept short, ideally less than 10cms. If you want a DAC more remote from the Beaglebone I would suggest using something like a pair of Twisted Pear Audio Teleporter modules which use LVDS (Low voltage differential signalling)

Are there inputs for the dac so a disc player can be hooked up?

Yes, the DAC can accept a conventional coax spdif input. Alternatively, you could access the I2S signal inside the transport and use teleporters to send that to the DAC.

Can you swap dac boards if you don't like the sound of one?

If you want to experiment with different DACs I would suggest using a breadboard approach initially, you can box up in a nice chassis once you find what you like.

Ray

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Post by Ray P » Wed Apr 01, 2015 8:40 pm

An update on my DAC build that featured at the top of this thread...

Still delighted with the sound quality and it's proving very reliable/consistent with no glitches or hangs with the Beaglebone.

Anyway, I'm now starting to experiment with DSD. The botic Linux distribution that is at the heart of the renderer can accept streamed DSD (not DoP) and the DAC will happily process DSD so it would be a shame not to use it.

To achieve that in my infrastructure I need a UPnP media server capable of serving DSD and a small addition to the Beaglebone.

I use Asset UPnP as my media server and a Beta release of version 5 is now available that can stream DSD, so I've downloaded that and installed it on my laptop. I've use it to play DSD on JRiver and it seems to work well (though JRiver obviously transcodes DSD to PCM for playback on the computer). Asset V5 for QNAP (my NAS) is a couple of months away. Incidentally, Asset is also available for the RPi platform now.

The change needed to the Beaglebone relates to the pins designated for output of PCM and DSD, they are different. I'm just waiting for a small daughter board that will remap the correct header pins to the output connectors having detected whether the data is DSD or PCM. A quick install and I should be listening to DSD streamed over the network.

Incidentally, just to illustrate the capability of the Beaglebone Black with the Botic linux distribution the following data types/rates are tested and all clocked at native sample rates;

PCM (16 & 24bit)
44.1KHz
48KHz
88.2KHz
96KHz
176.4KHz
192KHz
354.8KHz
384KHz
DSD
DSD64
DSD128

I'll update in due course.

Ray

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Post by solarflight » Wed Apr 08, 2015 9:41 pm

Thanks Ray P for the answers and the update. Much appreciated.

It looks like the Twisted Pear and Acko boards are now available.

Some other (probably basic) questions

Having the clocks connected to the BBB through the boards... Would that also be beneficial for dacs connected through the BBB usb?

Do the clocks/boards need additional power?

My idea is to perhaps start with the streamer first and then continue by adding a dac through I2S. Buffalo, Acko, Soekris or DDDAC...

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Post by Ray P » Thu Apr 09, 2015 7:17 am

solarflight wrote:Having the clocks connected to the BBB through the boards... Would that also be beneficial for dacs connected through the BBB usb?
The main benefit of the external clocking of the BBB is the preservation of native sample rates, avoiding resampling (the BBB's onboard clock can handle 48KHz data family rates but 44.1KHz data rates are resampled to 48KHz) or other compromises (such as the RPi's fractional division of its onboard clock signal to derive 44.1 and 48KHz clocking. Additionally, you use rather better oscillators, which is why I feed my BBB external clock signals for both 44.1 and 48KHz, though downstream the data will be reclocked with the same clocks by the Acko SO3 (or TPA's equivalent). Anyway, that main benefit of preserving native sample rates would seem to be applicable in a USB DAC context and I guess it will work but to me the USB approach loses out on the benefits of the downstream i2s data isolation and reclocking offered by the Acko and TPA boards?
solarflight wrote:Do the clocks/boards need additional power?
Yes, the isolator/reclocking boards require a power source. The Acko SO3 has three onboard regulators and you could have a discrete power source for each of those. Good quality power supplies are beneficial; I use a single Salas Reflektor-D shunt regulator to power my SO3. You also need to separately power the 'upstream' side of the isolators but that is provided by the BBB (3.3V is available on the P9 header).
solarflight wrote:My idea is to perhaps start with the streamer first and then continue by adding a dac through I2S. Buffalo, Acko, Soekris or DDDAC...
The renderer (BBB and isolator/reclocker) are the constants so that makes sense but be aware that the i2s connectors/interface with those different DACs are not the same so you'll need to build in some flexibility to connect each of them up. Acko, and others, are selling some little interface boards that cater for the different connections. If you plan to use ufl cables bear in mind that a specialist tool is recommended for disconnecting them (not cheap!). Other considerations;

- the Soekris DAC firmware is 'incomplete' at this time though I believe at least one person is successfully using the DAC with the BBB/Botic renderer (no need for a board such as the Acko SO3 as the Soekris has integrated isolation and a programmable onboard clock).

- if you want to try DSD sometime you wont be able to with the DDDAC and it is on the 'to do' list with the Soekris (via DoP), though I believe Doede (of DDDAC) is working on a discrete DSD DAC design that sounds very promising.

Let me know if I can help further. Good luck.

Ray

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