Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Filter brewing for the Soekris R2R
Filter brewing for the Soekris R2R
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 3rd March 2015, 07:22 PM   #281
oneoclock is offline oneoclock  Europe
diyAudio Member
 
oneoclock's Avatar
 
Join Date: Oct 2010
Quote:
Originally Posted by robertrowett View Post
Why is this so loud? Using passive volume control after direct output it is 90db at 7:00. Paul's NOS bypass v1 needs to be @ 5:00 for same output.
All other filters have been around 11:00 on analog volume control, except the original NOS which was 2-3:00.
Quote:
Originally Posted by oneoclock View Post
I do not use potentiometer, the gain is always 0 dB.
If you are using volume potentiometer, you should use this NOS-15 filter (-15 dB F1) to avoid saturation at +15 dB.
  Reply With Quote
Old 3rd March 2015, 10:47 PM   #282
spzzzzkt is offline spzzzzkt  Australia
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
Quote:
Originally Posted by oneoclock View Post
I do not use potentiometer, the gain is always 0 dB.
If you are using volume potentiometer, you should use this NOS-15 filter (-15 dB F1) to avoid saturation at +15 dB.
I think this misses the point of the 0db to +15dB range. Søren has commented that this is intended as make up gain for very quiet sources, and that for normal usage 0dB is the maximum that should be used. Søren also noted that adding gain will cause clipping if used with sources with adequate levels.

I personally wouldn't be adding attenuation which makes the gain settings a requirement for normal listening rather than an optional boost range as it cripples the intended functionality.

Last edited by spzzzzkt; 3rd March 2015 at 10:57 PM.
  Reply With Quote
Old 3rd March 2015, 11:04 PM   #283
robertrowett is offline robertrowett  United States
diyAudio Member
 
Join Date: Apr 2012
Quote:
Originally Posted by spzzzzkt View Post
I think this misses the point of the 0db to +15dB range. Søren has commented that this is intended as make up gain for very quiet sources, and that for normal usage 0dB is the maximum that should be used. Søren also noted that adding gain will cause clipping if used with sources with adequate levels.

I personally wouldn't be adding attenuation which makes the gain settings a requirement for normal listening rather than an optional boost range as it cripples the intended functionality.
All of the NOS filters clip except the original one from last month and the new fullbypass 1 (no gain). fullbypass 2, 3, NOS, and NOS-15 all clip in my system.
  Reply With Quote
Old 4th March 2015, 01:23 AM   #284
spzzzzkt is offline spzzzzkt  Australia
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
Quote:
Originally Posted by robertrowett View Post
All of the NOS filters clip except the original one from last month and the new fullbypass 1 (no gain). fullbypass 2, 3, NOS, and NOS-15 all clip in my system.
Fullbypass 2 and especially 3 were experiments to see if the filters would clip due to the added gain, so no surprises there. NOS and NOS-15 really shouldn't clip so there must be another factor in play...
  Reply With Quote
Old 4th March 2015, 01:42 AM   #285
spzzzzkt is offline spzzzzkt  Australia
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
Quote:
Originally Posted by spzzzzkt View Post
NOS and NOS-15 really shouldn't clip so there must be another factor in play...
Correction, a quick glance at the config indicates that NOS and NOS-15 will both clip badly.
  Reply With Quote
Old 4th March 2015, 02:05 AM   #286
spzzzzkt is offline spzzzzkt  Australia
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
OK, this should be as per Søren's suggested config and minus the x64 gain applied in oneoclock's NOS filters. I've also pasted in pos' revised De-emph filters.

This one shouldn't clip and should be roughly same volume as most filters. with any luck
Attached Files
File Type: txt 1021filtNewNOS.txt (1.6 KB, 241 views)
File Type: zip 1021filtNewNOS.skr.zip (564 Bytes, 275 views)
  Reply With Quote
Old 4th March 2015, 02:20 AM   #287
spzzzzkt is offline spzzzzkt  Australia
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
This is a slight variation on the above. I'm calling NQR - not quite right - because it's a mid-way position between my (botched) full bypass filter and the Søren-style NOS.

The mod I've made is to alter the filter coefficients from the correct
Code:
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
to the "not quite right"
Code:
0.000
0.000
1.000
1.000
1.000
1.000
0.000
0.000
This only applies to the 44.1 and 48kHz and moves the sinc roll-off up, so the response is only roughly 1dB down at 20kHz. The output using this filter will also be around -6dB on the correct NOS config.

Add: Just had a thought that it might be better reducing the filter taps to 4 rather than adding the 0.0 values. I suspect the zeros make this act as a rectangular filter and will increase distortion.
Attached Files
File Type: txt 1021filtNQR_NOS.txt (1.6 KB, 87 views)
File Type: zip 1021filtNQR_NOS.skr.zip (577 Bytes, 91 views)

Last edited by spzzzzkt; 4th March 2015 at 02:24 AM.
  Reply With Quote
Old 4th March 2015, 02:55 AM   #288
robertrowett is offline robertrowett  United States
diyAudio Member
 
Join Date: Apr 2012
Quote:
Originally Posted by spzzzzkt View Post
This is a slight variation on the above. I'm calling NQR - not quite right - because it's a mid-way position between my (botched) full bypass filter and the Søren-style NOS.

The mod I've made is to alter the filter coefficients from the correct
Code:
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
to the "not quite right"
Code:
0.000
0.000
1.000
1.000
1.000
1.000
0.000
0.000
This only applies to the 44.1 and 48kHz and moves the sinc roll-off up, so the response is only roughly 1dB down at 20kHz. The output using this filter will also be around -6dB on the correct NOS config.

Add: Just had a thought that it might be better reducing the filter taps to 4 rather than adding the 0.0 values. I suspect the zeros make this act as a rectangular filter and will increase distortion.
Thanks Paul. I loaded these up with your SA2v2 and look forward to listening this evening!
  Reply With Quote
Old 4th March 2015, 09:14 AM   #289
zfe is offline zfe
diyAudio Member
 
Join Date: Dec 2014
After thinking longer about what I have seen as output of the bypass filter (the output should reach full level (2V), which it does not (0.73V). FIR1=FIR2= one tab 1, multiplier 1), I realized that this is (physical) attenuation due to the "final analog filter"and not a fault of zero-insertion by itself. We have
U_out= U_sig (1-exp(-t/(R C))
so U_out is scaled down by a constant factor.
Here U_sig is the desired signal level, t=1/(64*44.1kHz), C=470pF the capacitance of the filter capacitor, R the internal resistance of the DAC as a voltage source.

So the "problem" is that RC is to high and the DAC needs several similar samples of the final sample rate of about 3MHz, so a FIR2 filter, to come near U_sig.
As we want to filter anyhow and are not designing a MHz AWG signal generator this is not really an issue, I think. But...

The easiest way to get a more text-book like output with the bypass filters, is to lower or remove C.
The harder thing to lower the internal resistance R (perhaps better bypass capacitors at the shift register or lowering/removing the resistor between the voltage regulator and the shift register ... but that is fiddling with the supply of the DAC ladder.
Click the image to open in full size.
Attached Images
File Type: jpg Bypass.jpg (122.7 KB, 85 views)
File Type: jpg SE1.jpg (154.5 KB, 82 views)
File Type: jpg SE2.jpg (186.2 KB, 76 views)
  Reply With Quote
Old 4th March 2015, 11:18 AM   #290
oneoclock is offline oneoclock  Europe
diyAudio Member
 
oneoclock's Avatar
 
Join Date: Oct 2010
Quote:
Originally Posted by spzzzzkt View Post
Correction, a quick glance at the config indicates that NOS and NOS-15 will both clip badly.
Format: signature, samplerate, interpolationrate, type, numbercoefficients, multiplier

What is multiplier? Is the gain?
  Reply With Quote

Reply


Filter brewing for the Soekris R2RHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Soekris 's DAC implementations Eldam Digital Line Level 1041 10th September 2017 12:00 AM
Sold: Soekris DAM1021 R2R DAC Eldam Swap Meet 6 6th February 2015 08:23 AM
24-bit R2R DAC using miltiple 16/18/20-bit R2R chips Marek Digital Source 21 1st April 2011 10:05 PM
project brewing in my head, challenging, but seem like a good way to try new concepts lemans23 Multi-Way 26 11th October 2005 01:29 PM


New To Site? Need Help?

All times are GMT. The time now is 02:14 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki