DIYHiFi.org

For the sake of audio
It is currently Mon Dec 18, 2017 8:36 pm

All times are UTC




Post new topic Reply to topic  [ 35 posts ]  Go to page Previous  1, 2, 3
Author Message
PostPosted: Wed Jun 25, 2014 3:49 am 
Offline
Cow

Joined: Tue Apr 01, 2014 1:47 am
Posts: 131
Location: Knoxville, Tn
Kuei Yang Wang wrote:
Kuei Yang Wang wrote:
Here my settings:


Attachment:
J-River ASIO Proxy #2.jpg


These work with iDSD nano.

Ciao T



Hi T.

Yes, I can get native ASIO working just fine now. It works with DSD, and works with all PCM sample rates that are 44.1 based. If it is 48 based, it doesn't work.

If I use DoP, both sets of PCM rates work.

Thanks

Andrew


Top
 Profile  
Reply with quote  
PostPosted: Wed Jun 25, 2014 10:47 am 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1168
Hi,

ball3901 wrote:
Yes, I can get native ASIO working just fine now. It works with DSD, and works with all PCM sample rates that are 44.1 based. If it is 48 based, it doesn't work.


Yes, that is because the ASIO DSD Spec was written when all DSD was 44.1KHz based.

ball3901 wrote:
If I use DoP, both sets of PCM rates work.


Yes, DOP supports illegal rates for DSD.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
PostPosted: Wed Jun 25, 2014 11:51 pm 
Offline
Cow

Joined: Tue Apr 01, 2014 1:47 am
Posts: 131
Location: Knoxville, Tn
ball3901 wrote:
Why is a reconstruction filter used at all when converting for PCM to DSD?? Seems unneeded to me. Looks like Jriver is applying a basic linear phase filter to PCM before oversampling and noiseshaping. Why? If you are oversampling to 2.8mhz or more, why would you need that kind of filter? I just don't see why anti-aliasing is needed at that rate.

Similarly, I notice that Burr Brown oversamples in its Delta Sigma converters first with an 8x oversampling filter, which can be linear phase, minimum phase etc. Then another interpolation stage, at an additional 8x or 16x or whatever is needed. Why not just a single 64x or 128x interpolation, with no reconstruction filter at all?

Obviously there is a reason PCM is anti-aliased before being Delta-Sigma modulated.

Trying to figure out why.

Thanks

Andrew



So, I think I found the answer to my question. CPU load. Oversampling to say, 8x, then oversampling a second time is a less CPU intensive process than a single oversample to say, 64x.

Still, seems ASIO proxy found a better way to do it that a standard linear phase filter.

And if it were me, I think i would use a single oversampling filter x64 or x128, etc. Not worry about aliasing and use as gentle a filter as I could.


Top
 Profile  
Reply with quote  
PostPosted: Sat Jun 28, 2014 2:50 pm 
Offline
Cow

Joined: Tue Apr 01, 2014 1:47 am
Posts: 131
Location: Knoxville, Tn
T,

When using ASIO proxy, specifically with SDM A and to a lesser extent C, I can hear low levels of quantization noise, in quiet passages etc.

Since you have looked at the output on the scope, is that an expected side effect of the modulator being used? Or is it more likely an issue with my CPU? For instance, using the same modulation mode, changed to floating point processing, the issue clears up.


Thanks

Andrew


Top
 Profile  
Reply with quote  
PostPosted: Sun Jun 29, 2014 3:55 am 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1168
Hi,

ball3901 wrote:
When using ASIO proxy, specifically with SDM A and to a lesser extent C, I can hear low levels of quantization noise, in quiet passages etc.

Since you have looked at the output on the scope, is that an expected side effect of the modulator being used? Or is it more likely an issue with my CPU? For instance, using the same modulation mode, changed to floating point processing, the issue clears up.


Have not looked that hard tbh.

You can buy a Rigol DS1052 on e-bay for under 300 bux and look yourself.

I ended up on C-float myself.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 35 posts ]  Go to page Previous  1, 2, 3

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group