Filter brewing for the Soekris R2R - Page 34 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Line Level
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th March 2015, 08:56 AM   #331
diyAudio Member
 
oneoclock's Avatar
 
Join Date: Oct 2010
Quote:
Originally Posted by new2hifi View Post
Now why NOS has less than perfect impulse response with both pre and post ringing present?
NOS have analog filter output, a C on the output. That's why we have impulse with a few pre and pos ringing.
  Reply With Quote
Old 7th March 2015, 08:59 AM   #332
diyAudio Member
 
Join Date: Feb 2009
Quote:
Originally Posted by oneoclock View Post
NOS have analog filter output, a C on the output. That's why we have impulse with a few pre and pos ringing.
I am pretty sure the motu soundcard ADC is ringing, the capacitor on the output of the dam will not have any preringing at all and only very very little post....
On the scope NOS shows no traces of ringing.

Last edited by hop.sing; 7th March 2015 at 09:05 AM.
  Reply With Quote
Old 7th March 2015, 10:20 AM   #333
diyAudio Member
 
Overkill Audio's Avatar
 
Join Date: Oct 2006
Quote:
Originally Posted by zfe View Post

The ultimate goal would be a DAM-simulator for the digital output, taking also in account the fixed point arithmetic in the FPGA. To an certain extend this could be done, but at some point we would need implementation details of Soren.

This would make the filter development process much more accurate and efficient.....Fantastic if you can do this!
Thanks
Derek.
__________________
" This is not the end, not even the beginning of the end, but it is the end of the beginning "
Sir Winston Churchill 1943
  Reply With Quote
Old 7th March 2015, 10:23 AM   #334
diyAudio Member
 
Join Date: Jun 2004
Location: NZ
Quote:
Originally Posted by oneoclock View Post
NOS have analog filter output, a C on the output. That's why we have impulse with a few pre and pos ringing.
A first order rc filter cannot have any pre-ringing, and has no post ringing either.
  Reply With Quote
Old 7th March 2015, 07:00 PM   #335
diyAudio Member
 
oneoclock's Avatar
 
Join Date: Oct 2010
Quote:
Originally Posted by gazzagazza View Post
A first order rc filter cannot have any pre-ringing, and has no post ringing either.
Well, my digital filtering measurement board then?
  Reply With Quote
Old 7th March 2015, 07:03 PM   #336
diyAudio Member
 
oneoclock's Avatar
 
Join Date: Oct 2010
More measures. With oscilloscope.
Attached Files
File Type: pdf Square1.pdf (520.2 KB, 82 views)
File Type: pdf square-NOS.pdf (975.1 KB, 86 views)
  Reply With Quote
Old 7th March 2015, 07:55 PM   #337
zfe is offline zfe
diyAudio Member
 
Join Date: Dec 2014
The full amplitude NOS filter problem could be related with the "problem" of the DAM of handling the maximal alowed negative ampltude.

Quote:
Originally Posted by zfe View Post
... @ Soren:
There problem with how the DAM handles the maximal negative sample in the PCM data.
Lets say we use 24bit. According the WAV/PCM specifications the negative numbers are the two-complements and x80 00 00 is the the maximal allowed negative number. The DAM (USB-Amareno) reproduces this a zero. x80 00 01 gives the maximal negative spike.
So you could say there is some extreme clipping for just one value of the amplitud (the max negative one).
This applies to the amplitude after filtering. So the direct correspondence to the PCM aplitude is only given with the bypass or NOS filter.

With 32 bit data high negative amplitudes such as x80 00 00 01 seem to be truncated to 24 or 28 bit and thus lead also to no impuls instead of a maximal negative impulse.

This is probably due to the fact that the natural signal range of a sign magnitude DAC is +2^n-1 to -(2^n-1) and that the allowed range in PCM data is +2^n-1 to -2^n, and some "special case" handeling is missing in the code.

Soren promised a fix of that with the next firmware.

Last edited by zfe; 7th March 2015 at 08:10 PM.
  Reply With Quote
Old 8th March 2015, 04:04 AM   #338
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
Blog Entries: 1
Quote:
Originally Posted by oneoclock View Post
More measures. With oscilloscope.
That is great work!

So the Signal Suite test signal is varying?
Looks like I need to go back to .wav files.
  Reply With Quote
Old 8th March 2015, 04:21 AM   #339
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
Blog Entries: 1
Quote:
Originally Posted by zfe View Post
Soren promised a fix of that with the next firmware.
The clipping seems to occur on both positive and negative maxima. Would truncating the negative only have this effect?
  Reply With Quote
Old 8th March 2015, 08:28 AM   #340
zfe is offline zfe
diyAudio Member
 
Join Date: Dec 2014
Quote:
Originally Posted by spzzzzkt View Post
The clipping seems to occur on both positive and negative maxima. Would truncating the negative only have this effect?
My comment was thought as possible explanation of the higher distortion of NOS 0dB plot in the second PDF.

I am quite sure, the obvious clipping of the square wave with the added small sinus should be no "fault" of the DAM but just an effect of the filter+gain, i.e. the (digital) signal after being filtered and gain adjusting contains values above the maximum allowed digital signal which then are "clipped" to the maximum (as nothing higher can be handled by the DAC ladder).

You should be able to see that also with sox, applying there the filters and gain, clipping should be reported.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Soekris 's DAC implementations Eldam Digital Line Level 1038 20th April 2017 05:30 PM
Sold: Soekris DAM1021 R2R DAC Eldam Swap Meet 6 6th February 2015 07:23 AM
24-bit R2R DAC using miltiple 16/18/20-bit R2R chips Marek Digital Source 21 1st April 2011 09:05 PM
project brewing in my head, challenging, but seem like a good way to try new concepts lemans23 Multi-Way 26 11th October 2005 12:29 PM


New To Site? Need Help?

All times are GMT. The time now is 08:06 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki