Introducing the Ozone DAC platform
Posted 9th October 2013 at 11:51 AM by abraxalito
The time has come to talk about the overall aim of my DAC developments - a modular DAC platform for DIYers and audio systems integrators. By this word 'platform' I mean this isn't going to be presented as a single end-to-end design that you can order up from a friendly reseller. Nor is this an 'open source' design, although it is open to anyone to use or adapt with no restrictions. Rather this is a DIYer's DAC architecture a series of interconnected modules that are subsystems from which an audiophile grade DAC can be assembled.
When I say 'audiophile grade' what I mean is this is a design optimized for aural satisfaction, not for the numbers. To be even more specific, its been optimized to give the highest perceived dynamics (within the limitations of the chosen DAC chip) rather than the lowest THD+N and flattest FR. If you're looking for ODAC-type measurements, feel free to move along now
That's not to say measurements have been ignored, rather they're very much in the back seat. This is very much a music lover's, rather than meter lover's DAC.
What's to follow is all rather tentative, but I see there being 6 modular aspects to this, they are at various stages of development (including totally un-started!).
No.1 is the motherboard, with input and output connectors, power supply parts and some interfaces.
N0.2 is the input subsystem - be it USB or S/PDIF or even eventually HDMI.
No.3 is the digital engine - this to receive I2S from the previous module and do whatever processing is called for. Initially this will probably just be my I2S transcoder but eventually it will include an ARM CPU and perhaps the LAID delay registers.
No.4 is the DAC engine proper, consisting of multiple (two or more) TDA1545 or TDA1387s in a differential configuration. It provides a balanced current output to board no.5
No.5 is the passive (LC) filter board, balanced in, balanced out. Perhaps interfaced via SATA connectors, no power being required.
No.6 is the analog backend, with pre-amp, volume control and output buffering functions with sufficient umph to drive IEMS (16ohms) via hand-wound transformers.
Comments, questions, brick-bats?
When I say 'audiophile grade' what I mean is this is a design optimized for aural satisfaction, not for the numbers. To be even more specific, its been optimized to give the highest perceived dynamics (within the limitations of the chosen DAC chip) rather than the lowest THD+N and flattest FR. If you're looking for ODAC-type measurements, feel free to move along now
That's not to say measurements have been ignored, rather they're very much in the back seat. This is very much a music lover's, rather than meter lover's DAC.What's to follow is all rather tentative, but I see there being 6 modular aspects to this, they are at various stages of development (including totally un-started!).
No.1 is the motherboard, with input and output connectors, power supply parts and some interfaces.
N0.2 is the input subsystem - be it USB or S/PDIF or even eventually HDMI.
No.3 is the digital engine - this to receive I2S from the previous module and do whatever processing is called for. Initially this will probably just be my I2S transcoder but eventually it will include an ARM CPU and perhaps the LAID delay registers.
No.4 is the DAC engine proper, consisting of multiple (two or more) TDA1545 or TDA1387s in a differential configuration. It provides a balanced current output to board no.5
No.5 is the passive (LC) filter board, balanced in, balanced out. Perhaps interfaced via SATA connectors, no power being required.
No.6 is the analog backend, with pre-amp, volume control and output buffering functions with sufficient umph to drive IEMS (16ohms) via hand-wound transformers.
Comments, questions, brick-bats?
Total Comments 8
Comments
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Nice, very nice, Richard ... looks like you're becoming our very own Ben Duncan, ;) ...
FrankPosted 9th October 2013 at 10:57 PM by fas42
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Having got the niceties over with straightaway, :D, I guess my number one 'concern' would be the way the modules are interfaced - to me, the very fact that the functions are modularised is immediately introducing an area of possible 'weakness' - if I wasn't happy with the sound that's the first place I would be looking at, for answers ...
FrankPosted 9th October 2013 at 11:05 PM by fas42
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Thanks Frank - Ben Duncan's preamp articles (AMP-01) in HFNRR were fairly strongly instrumental in getting me on the audio design ladder so that's a nice compliment!
Yes I share your concerns about interfacing - its hard to come up with a way to make things modular (for the flexibility) and yet not suffer from interconnection difficulties. That's as yet untested so I'm making it all up as I go along.... I have used SATA for connections between DAC and poweramp in the past - apart from it being easy to buy bad cables here, have not yet noticed any probs. Early days though.Posted 10th October 2013 at 02:11 AM by abraxalito
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I'm currently experimenting with a 'no active voltage gain' DAC. The idea is that the I/V is done directly to line level, meaning no preamp function (by which I mean internal gain stage, not preamp audio component) is needed. For almost all my DACs to-date, I've needed gain as the passive filter loses 6dB and its been much easier to build passive filters that operate at lower impedances as the inductor sizes are more managable. For this incarnation though I threw caution to the wind and wound 32 55mH inductors so the filter can operate at a high enough impedance level. And guess what - it sounds even more dynamic! I am just using some classA buffers to take the filtered I/V output to a transformer, doing bal-SE conversation. Best DAC I've ever heard
In fact so good that I'm giving up DAC development work now to concentrate on building an amp that does it justice...Posted 10th November 2013 at 12:29 AM by abraxalito
Updated 10th November 2013 at 12:35 AM by abraxalito -
Encouraging progress report ... also sounds familiar, one side of the system gets jacked up enough so that one realises that another area is slumping, falling behind, relatively speaking - so a change of focus needed ...
The marvellous thing is that this iterative process seems to know no bounds, the hints I've had at times of where the sound can get to, if other hurdles are properly tackled to give true, long-term solutions, has always re-energised me, for the next round, :) ...Posted 10th November 2013 at 11:36 AM by fas42
Updated 10th November 2013 at 11:39 AM by fas42 -
Yep its the constant re-energization that perhaps, there's a hitherto unsighted peak in audio experience visible once we've scaled the current one
ClassA amp is the project in gestation now - one which will present an unvarying load to the power supply by virtue of being CCS loaded. Terrible inefficiency of course but hey, winter's coming (not where you are though).Posted 10th November 2013 at 11:56 PM by abraxalito
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Wouldn't believe it today ... finally had decent rain after 4 months of virtual drought, went to the railway station, literally a stone's throw away, this morning and the waiting room had the heater on ...
Australian weather gets pretty crazy at times, and it's only becoming worse ...Posted 11th November 2013 at 12:36 AM by fas42
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Whilst on the general topic of insanity, my IP was blocked from accessing WBF just about a week ago. Can still read it at my school though - means I don't waste as much time at homePosted 11th November 2013 at 01:49 AM by abraxalito
