So the question is, "will the basic nuts and bolts fit onto a BBB cape or SO3/4 that one happens to have under development"?🙂
cos, someone rubbed the Lamp
There is a diy discrete DSD DAC, which I will be the first few recieving one.Can't let the cat out just yet...
I am a little inclined to add one to the output of the upcoming S04 board but advice from bkdog tend to favour an external filter... so maybe not, will see.
So a nice filter design is the key....
cos, someone rubbed the Lamp
As it’s already been posted elsewhere on the forum, and we got permission from Doede for this, I can probably elaborate a little more. I was one of the few lucky ones to be present at the unveiling of Doede’s his new project/ breadboard proto type of his discrete DSD dac design, a couple of weeks ago.
Here’s a short write-up I made of the event: http://www.diyaudio.com/forums/digital-line-level/224108-nos-192-24-dac-pcm1794-waveio-usb-input-411.html#post4242133
James and Stefan, who were also present, wrote about their impression a few posts later in that thread.
The small glimps of the potential we caught of this new dac concept sounded excellent.
In my mind, this new design concept is going to be a game changer. What we gathered from Doede was that the filtering was still one of the sticky points.
Acko, as you are obviously a very gifted engineer, I guess the words “discrete” & “DSD” were enough for you to put one and two together. 🙂 I ‘m curious to see what your take might be and if you’ll be able to crack the problem.
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Very impressive efforts!
Sorry, I didn't mean to encroach on your ideas and Chanh did not actually reveal any plans. For I while I was convinced that DSD did not require a processing unit to decode in order to render the modulating signal. Yet every other manufacturer indicated otherwise or somehow entangled with their proprietary techniques. This contradicts with the physical nature of DSD which is essentially Pulse Density Modulation, similar to PWM used in switch-mode PSU and motor drives. So my response to Chanh's post was more of frustration rather than reading between the lines - more like, there goes another DSD DAC with top secret technology!
Anyway, this is really very new to me and I am actually behind the curve but essentially we need a top quality filter design. I have shown a simple RC filter but since been advised that this is not enough. We need to look at the spectral analysis of DSD or this PDM and from which we craft an optimized filter. Filter design is beyond my expertise so any help from those knowledgeable will be appreciated.
I am also thinking with this simplicity of DSD, DACs like 9018 will find no trouble "processing" it compared with the efforts in up sampling and decoding PCM. And then it takes care of the filtering within the chip - nice and easy.
Then, there are different schools of thought like DSD is closer to the original analog signal as you can practically see the signature in the pulses.
On the other hand many are steadfast convinced that joining the dots in a decoded PCM is much more realistic than extracting signals from a switch-mode signal.
So all remains to be seen.....
Btw, thanks for the compliments and wish you all success in your efforts.
Hi Acko, I have no credit in any of this. I'm looking forward to seeing where all of this is going.
Looking more like FM, so for someone who also understands radio technology very well ...
I think I need to go back to my college books!
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Yes indeed! It was very impressive. Even through the hashy noise of this breadboard prototype it was clear that this was next level and something really special 🙂
Yes, that was Doede's thinking too it seems. Keep it as simple as possible and use the dsd signal to modulate a mossfet and create the output signal.
That side of things seems to work very nice if you find the right components, so the real challenge is filtering the noise. I believe Doede was proposing to use an averaging filter for this.
I really like the idea of using software to convert to DSD, then having the hardware as clean and simple as possible. I'd love to hear a version using a nice valve instead of a mossfet too 🙂
Also, the DSD signature closely matches the processing architecture of a sigma-delta DAC, so leaning nicely to the 9018 DAC, if DAC is used that is , my two cents 🙂
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The only issue I found based on my personal experience was ES9018 sonic signature too synthetic, analytical alike. If precision, accuracy, and clean sound, it is spot on. If musical is what we looking for, it is too thin timbre, no weight, no body, no realism!
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Sorry I typed on the go with out second read. Might offended some readers.
Any way, We did both DSD and PCM. Tests were carried out on a tweaked BSE with Lundalh output transformers and linear ps. I guess the observations are purely personal taste. Btw, when doing the shoot out, AK4490 to my ears was a more engaging than ES9018 in term of overall SQ. May be Lintweaker would share his thoughts between the two?
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Any way, We did both DSD and PCM. Tests were carried out on a tweaked BSE with Lundalh output transformers and linear ps. I guess the observations are purely personal taste. Btw, when doing the shoot out, AK4490 to my ears was a more engaging than ES9018 in term of overall SQ. May be Lintweaker would share his thoughts between the two?
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I think you better discuss this with Mick, SuperTek designer. I was not suppose to disclose his works publicly. 🙂
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All interesting stuff and some well documented experiences from stijn, et al. I don't have the technical ability to contribute on a technical level though so I should have been a bit clearer about what I meant with my earlier comment - I didn't expect a whole DSD DAC to be squeezed onto an SO3;
It would seem to me that you end up with two DACs in parallel, one optimised for PCM and the other for DSD, which implies a second set of outputs on the SO3 or supercape (i.e the basic nuts and bolts).
If it was appropriate to have the two DACs in a single chassis, perhaps sharing a common output buffer (and analogue attenuator?) it might be useful to use the PCM/DSD select switch function available from something like the BBBotic to automatically route the PCM/DSD data streams to the right set of SO3+ outputs and to switch the buffer input to use the appropriate DAC as its source? Just thinking about how separate PCM/DSD DACs might work in a practical implementation - I realise the devil will be in the detail...
Is it just coincidence that a practical DIY Ladder type DAC design (Soekris) that seems to show good promise as a PCM DAC has emerged in a similar timescale to the DDDAC DSD approach?
Ray
It would seem to me that you end up with two DACs in parallel, one optimised for PCM and the other for DSD, which implies a second set of outputs on the SO3 or supercape (i.e the basic nuts and bolts).
If it was appropriate to have the two DACs in a single chassis, perhaps sharing a common output buffer (and analogue attenuator?) it might be useful to use the PCM/DSD select switch function available from something like the BBBotic to automatically route the PCM/DSD data streams to the right set of SO3+ outputs and to switch the buffer input to use the appropriate DAC as its source? Just thinking about how separate PCM/DSD DACs might work in a practical implementation - I realise the devil will be in the detail...
Is it just coincidence that a practical DIY Ladder type DAC design (Soekris) that seems to show good promise as a PCM DAC has emerged in a similar timescale to the DDDAC DSD approach?
Ray
Like James suggested, depending on the capabilities of the source device the better option in my mind would be to convert PCM to DSD and play out through a DSD capable chain.
Fair enough. I'll drop Mick an email later tonight. There's an IV I suggested to him a while back that's going to be available again soon. I think he'll like it. (opc's NTD1)
Chris
Chanh, thanks for the feedback and your listening impressions. It is always good to compare notes and I will keep this in mind 🙂