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Direct Drive DSD

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#461
acko said:
I will have double check on this AKM chip. AFAIK, Sonny's USB interface simply pulls strings on this DAC chip.

Yes, DSD conversion benefits and the lack of direct connection of Tidal to HQPlayer means Roon has to come in. Probably trial it for a year and see.

I will most likely adjust my DSD DAC design for direct connection to Tidal. Even HQplayer will become an option rather than core requirement as it is currently.
Click to expand...


Ahh ok so you decided to use an SRC chip? Or SRC in FPGA?
 
#474
acko said:
THD+N and DNR ~ -120dB - initial analysis based on device characterization
Click to expand...

Hi Acko, you seem to have been quietly plugging away with your DSD project and it seems to becoming more sophisticated with upsampling, isolation and reclocking and, if I'm correct, digital volume?

How is the filtering developing and is it still by-passable? A block diagram f your architecture would be usefu?

I encountered white-noise on the output when I experimented with a LP filter at 80K and used HQP for upsampling to DSD256 with the volume control enabled, no problem with HQP's volume control disabled.

Do you have an ETA and price sketched in yet?

Ray
 
#475
Hi Ray, I have been quite busy with this DSD DAC and there is still more work to do 😀
One thing that is becoming apparent now is that there are two types of DSD:
1. Natively recorded Hi-res material (Pure DSD)
2. Upsampled DSD (PCM-DSD)

DSD by nature is very noisy (generated noise) and the noise energy far exceeds that of the base signal. Upsampled ones are even worse with weird artifacts that can be difficult to remove. From the looks of it Upsampled "on-the-fly" DSD will the common use-case for a typical DSD DAC.

A simple LPF "NoDAC" may not be enough to remove ultrasonics to safe levels and sometimes may cause instability to amplifiers. So you may be experiencing these effects with some combinations of HQPlayer. I have also looked at Andrea Ciuffoli's work that is very similar and if you scroll down to the performance graphs, the THD+N for this simple setup is -68dB! (0.038%) ->AudioDesignGuide

I thought rather than rushing out to roll out boards it is best to see what sort of performance that can be realistically achieved.

So the figures stated earlier are for PCM 44.1k/16-bit to DSD
and this just in: for PureDSD direct: THD+N=-120dB and DNR=-130dB
These are based on theoretical analysis only and may be different in the final product but at least some indication that is it worth the candle to pursue further.

Things are still in a state of flux so I am afraid I cannot tell you at this stage how the final product and prices will look like. Most likely a complete DAC system first with everything integrated so that the performance can be fully evaluated. Yes, there will be Digital Volume control, filters etc all tuned to match so a full featured DAC. Some sections like Vol can be bypassed but not things like safety filters.
 
#476
acko said:
Hi Ray, I have been quite busy with this DSD DAC and there is still more work to do 😀
One thing that is becoming apparent now is that there are two types of DSD:
1. Natively recorded Hi-res material (Pure DSD)
2. Upsampled DSD (PCM-DSD)

DSD by nature is very noisy (generated noise) and the noise energy far exceeds that of the base signal. Upsampled ones are even worse with weird artifacts that can be difficult to remove. From the looks of it Upsampled "on-the-fly" DSD will the common use-case for a typical DSD DAC.

A simple LPF "NoDAC" may not be enough to remove ultrasonics to safe levels and sometimes may cause instability to amplifiers. So you may be experiencing these effects with some combinations of HQPlayer. I have also looked at Andrea Ciuffoli's work that is very similar and if you scroll down to the performance graphs, the THD+N for this simple setup is -68dB! (0.038%) ->AudioDesignGuide

I thought rather than rushing out to roll out boards it is best to see what sort of performance that can be realistically achieved.

So the figures stated earlier are for PCM 44.1k/16-bit to DSD
and this just in: for PureDSD direct: THD+N=-120dB and DNR=-130dB
These are based on theoretical analysis only and may be different in the final product but at least some indication that is it worth the candle to pursue further.

Things are still in a state of flux so I am afraid I cannot tell you at this stage how the final product and prices will look like. Most likely a complete DAC system first with everything integrated so that the performance can be fully evaluated. Yes, there will be Digital Volume control, filters etc all tuned to match so a full featured DAC. Some sections like Vol can be bypassed but not things like safety filters.
Click to expand...

Right on Acko. Any rough ETA of when your thinking you can expect a finished product?
 
#477
acko said:
...

DSD by nature is very noisy (generated noise) and the noise energy far exceeds that of the base signal. Upsampled ones are even worse with weird artifacts that can be difficult to remove. From the looks of it Upsampled "on-the-fly" DSD will the common use-case for a typical DSD DAC.

A simple LPF "NoDAC" may not be enough to remove ultrasonics to safe levels and sometimes may cause instability to amplifiers. So you may be experiencing these effects with some combinations of HQPlayer. I have also looked at Andrea Ciuffoli's work that is very similar and if you scroll down to the performance graphs, the THD+N for this simple setup is -68dB! (0.038%) ->AudioDesignGuide

...
Click to expand...

Thanks for the update Acko. Based on the evidence of the LP Filter PCB buy I'm running there is a lot of interest in DSD playback and a more 'sorted' project is going to be a natural follow on from the very simple approach.

To be honest Acko, I don't have the technical savvy to fully understand the performance graph on the link you posted and I rely on standing on the shoulders of giants, such as yourself. I do like the sounds produced though! I am familiar with the material on the link. One thing I did notice is, referring to the 'schematic' at the vey bottom of the page, the LP filter specified (R=3K3, C=3.3nF) will have a -3dB point at only about 15KHz - does that matter in this context?

Regarding the white noise I was experiencing with the HQP volume control engaged, here's what Jussi had to say;

http://www.computeraudiophile.com/f11-software/hq-player-20293/index190.html#post510464

http://www.computeraudiophile.com/f11-software/hq-player-20293/index190.html#post510578

On the simple LP filter front, I've acquired a pair of Silk STA522A TVCs. I plan to experiment with using them as a combined LP filter/volume control. Their bandwidth falls away quickly above around 35KHz. Thoughts?

SAC Thailand

Cheers

Ray
 
Last edited:
#478
nautibuoy said:
Thanks for the update Acko. Based on the evidence of the LP Filter PCB buy I'm running there is a lot of interest in DSD playback and a more 'sorted' project is going to be a natural follow on from the very simple approach.

To be honest Acko, I don't have the technical savvy to fully understand the performance graph on the link you posted and I rely on standing on the shoulders of giants, such as yourself. I do like the sounds produced though! I am familiar with the material on the link. One thing I did notice is, referring to the 'schematic' at the vey bottom of the page, the LP filter specified (R=3K3, C=3.3nF) will have a -3dB point at only about 15KHz - does that matter in this context?

Regarding the white noise I was experiencing with the HQP volume control engaged, here's what Jussi had to say;

HQ Player - Page 190

HQ Player - Page 190

On the simple LP filter front, I've acquired a pair of Silk STA522A TVCs. I plan to experiment with using them as a combined LP filter/volume control. Their bandwidth falls away quickly above around 35KHz. Thoughts?

SAC Thailand

Cheers

Ray
Click to expand...


Cheers Ray, I will have a look the details when I get a bit more time.

Question: How do plan to address the high energy noise that you can't hear?

STA522As are fantastic but not cheap so it adds to the overall costs. For all you know user may just use a simple LPF instead to save on costs and use headphones instead and in the process create a "dangerous prototype"
 
#479
@acko: .... this sounds indeed very interesting Acko ... looking forward to hearing more about this in due time ;-)

I have also looked at Andrea Ciuffoli's work that is very similar and if you scroll down to the performance graphs, the THD+N for this simple setup is -68dB! (0.038%) ->AudioDesignGuide
Click to expand...

One comment in relation to the link to Andrea Ciuffoli's webpages that you refer to. It looks as if the DSD rate is DSD128 and I reckon that both the ultra sonic noise and the distortion could drop if e.g. DSD512 were the playback rate ... Dont know how much, though ... (Maybe others have experiences here? My computer unfortunately barely manages DSD128 from HQPlayer and much more noise on JRiver and Foobar)

Also, recently I made a similar DSD "DAC" with two potsemi flip-flops as the active devices and a very solid PSU. Here I noticed that the distortion is heavily output current dependent. If I remember correctly (and I am not sure my memory is entirely correct here) the sweet spot was about 1 mA - below that the THD could actually be quite low.

Cheers,

Jesper
 
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