Filter brewing for the Soekris R2R - Page 80 - 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 18th April 2015, 08:55 PM   #791
Priidik is offline Priidik  Estonia
diyAudio Member
 
Join Date: Nov 2014
Location: Estonia
I have the C128-100 right now.
I had the original impression that the bass is a bit weak on Dam, but directly comparing to BMC Puredac showed that the Puredac does the same fluffy bass almost in every situation, while Dam has proper resolution. The other thing is that Dam showcases compression much more easily, great tracks explode while weak compressed recordings are lifeless and dull.
Sometimes i feel like the bass might be a bit soft, kind of like dropping wet cloth, maybe it should hit with sharper edge. Apparent with some drum kits. But this could be just my imagination.
  Reply With Quote
Old 18th April 2015, 11:32 PM   #792
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
Blog Entries: 1
Quote:
Originally Posted by danny_66 View Post
Hi Paul,
Do not confuse "more" bass with "better" bass.
I prefer a tight and detailed bass to a more present but blurry bass.
I try not to confuse the two

The other thing I should mention is that jitter reduction makes a difference to the bottom end in my experience. I haven't done a switch for a while but on my D1v3 the difference between CS8412 recovered clocking and clocked from a digital PLL controlled Tent Labs VCXO was most noticeable as a significant improvement tightness and definition of the bass. It sounds comparatively thin in the bottom end but it's actually focus instead of flab.

I listened to slow sine sweeps for about ten minutes yesterday, and I couldn't detect any obvious variation in levels between 45-1000Hz.

As a bit of context the speakers I'm using are Audiovector Mi1 Signatures. They are an oldish model from 2004. I got them last year as a ex-demo item from the company that had until recently been the local distributor. Haven't been able to find much in the anglophone press about them. Hifi News awarded the Mi1 Sigs "editors choice" in 2004 but can't locate the review that is based on.

If you can manage to make any sense of the mashed googletranlatelish there was a review in High Fidelity (poland). There is an award summary in english which says
Quote:
Audiovector is accompany true to its ideals for years, the most important is being true to the signal coming from the amplifier. Mi 1 Signature are the best example of that, because they play with incredibly clean, "transparent" sound with a very good treble.
https://translate.google.com.au/tran...tml&edit-text=

The system I listen on is DAM (buffered XLR, direct trafo powering) -> Hypex UcD180HG+HxRs -> Audiovector Mi1 Sigs, so very strongly biased towards clean, detailed and accurate rather than "sugar-coated".
  Reply With Quote
Old 18th April 2015, 11:47 PM   #793
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
Blog Entries: 1
Quote:
Originally Posted by Stixx View Post
DAM probably has less volume but a good deal more definition/detail. DAM easily sounds better than the Subbu not only bass-wise.
Quote:
Originally Posted by spikestabber View Post
I don't really see an issue with the bass, its certainly present and very well defined on my HD800 cans as well as my cheap KEF tower floor speakers. Its about what I expect for a system that has a flat frequency response.
Quote:
Originally Posted by zfe View Post
But by hazard, when moving around in the room, I noticed that at the right location (in the room) you still "feel some of the punch", but that location is different for different records.
I think it could be that the energy is now more precisely focused in space, whereas before you had it more or less everywhere.
Quote:
Originally Posted by Priidik View Post
The other thing is that Dam showcases compression much more easily, great tracks explode while weak compressed recordings are lifeless and dull.
Sometimes i feel like the bass might be a bit soft, kind of like dropping wet cloth, maybe it should hit with sharper edge. Apparent with some drum kits. But this could be just my imagination.
Thanks for the comments. I broadly agree with what is said.

Like zfe I've noticed that bass strength is very position dependent - probably due to room modes etc. However there are phase differences between the filters so that could be a contributing factor. The phase is linear in that it is constrained between -180 to +180 but phase changes within that range are non-identical. I've seen discussion of zero-phase filters which might be an interesting avenue to explore, but I don't think I can do zero-phase with the Nyquist filters.
  Reply With Quote
Old 19th April 2015, 06:19 AM   #794
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
Blog Entries: 1
Default Classic Brickwall Filter

This is just a really straight up brick wall filter - I thought it might be worth having as a reference point.

It's flat to 20kHz, and is fully attenuated at 22.05kHz, with 95dB passband attenuation. The filter is done with a standard algorithm, and uses a hamming window. Nothing special, and nothing has been done to optimise the length which is 1015 taps.
Attached Files
File Type: zip 1021filtClassicBW.skr.zip (4.2 KB, 32 views)
  Reply With Quote
Old 19th April 2015, 07:18 PM   #795
diyAudio Member
 
danny_66's Avatar
 
Join Date: Jun 2005
Location: Lierde
Quote:
Originally Posted by spzzzzkt View Post
As a bit of context the speakers I'm using are Audiovector Mi1 Signatures.
Seems good speakers, someone reviewed them and found them a bit light in the bass.
Just add some 10" woofers and you'll have your bass
__________________
My RefSpeaker
  Reply With Quote
Old 19th April 2015, 10:13 PM   #796
zfe is offline zfe
diyAudio Member
 
Join Date: Dec 2014
While experimenting with frequency response plots (with octave) I noticed two things:
1. For plots of details the standard setting (length of the DFT) is too short.
2. The effect of the reduced resolution of the coefficients is only visible in the stopband attenuation.

As Illustration. I use the stock FIR1 and FIR2 filter, the plots are for the combined filter (FIR1, upsample, FIR2).

First plot the frequency response up to the Nyqvist frequency. Green the full double resolution of the coefficients, red reduced to 30 bits.
You see my second point.
fir_response1.png

Next plot detail of the passband 20-18000Hz, obviously we have a problem with the frequency-wise resolution.
fir_response1det.png

Next plots with DFT length 2^18
For the full frequency range we get not much more information, only more oscillation in the stopband.
fir_response2.png

The detail plot of the passband now looks nice.
fir_response2det.png


Here the (surely not optimal) code I used to produce the plots:
Code:
pkg load signal;
global fs=64*44100;

fir1= dlmread("/path/fir1.txt");
fir2= dlmread("/path/fir2.txt");
fir = conv(upsample (fir1, 8), fir2, "full");

function red = res(x)
% reduce resolution of x to aproximately 30 bits
red= round(x*2^(30))/2.0^(30);
end;

function [fr,db] = fdb(Hi,fi) 
% transform x-y-axis
global fs;
fr= (fi/(2*pi))*fs;
db= 20*log10(abs(Hi));
end;

function [lr,ur,mi,ma] = pli(l,u, Hl,Hrl)
% min/max value for the detail plot
global fs;
lr=l;
ur=u;
a=max(1, idivide(2*l*length(Hl),fs));
b=idivide(2*u*length(Hl),fs)+1;
mi1=min(20*log10(abs(Hl(a:b))));
ma1=max(20*log10(abs(Hl(a:b))));
mi2=min(20*log10(abs(Hrl(a:b))));
ma2=max(20*log10(abs(Hrl(a:b))));
mi=min([mi1,mi2]);
ma=max([ma1,ma2]);
end;



[H,f] = freqz (fir);
fir_r=arrayfun(@res,fir); % reduced resolution to 30 bits
[Hr,f] = freqz (fir_r);
[a,b]=fdb(H,f);
[c,d]=fdb(Hr,f);
plot(a,b,'g',c,d,'r');
xlabel('Frequency (hz)');
ylabel('Amplitude Response (dB)');
axis([0.1, fs/2, -250, 10]);
grid('on');
print -FHelvetica -r300 -dpng fir_response1.png;

[lr,ur,mi,ma] = pli(20,18000, H,Hr);
axis([lr,ur,mi,ma] );
grid('on');
print -FHelvetica -r300 -dpng fir_response1det.png;

% long DFT
[H,f] = freqz (fir,1,2^(18));
[Hr,f] = freqz (fir_r,1,2^(18));
[a,b]=fdb(H,f);
[c,d]=fdb(Hr,f);
plot(a,b,'g',c,d,'r');
xlabel('Frequency (hz)');
ylabel('Amplitude Response (dB)');
axis([0.1, fs/2, -200, 10]);
grid('on');
print -FHelvetica -r300 -dpng fir_response2.png;

[lr,ur,mi,ma] = pli(20,18000, H,Hr);
axis([lr,ur,mi,ma] );
grid('on');
print -FHelvetica -r300 -dpng fir_response2det.png;

Last edited by zfe; 19th April 2015 at 10:34 PM.
  Reply With Quote
Old 19th April 2015, 10:28 PM   #797
zfe is offline zfe
diyAudio Member
 
Join Date: Dec 2014
Quote:
Originally Posted by spzzzzkt View Post
The phase is linear in that it is constrained between -180 to +180 but phase changes within that range are non-identical. I've seen discussion of zero-phase filters which might be an interesting avenue to explore
I thought linear phase is just zero phase plus latency/delay in time ...?
  Reply With Quote
Old 19th April 2015, 11:27 PM   #798
diyAudio Member
 
Join Date: May 2005
Location: Melbourne
Blog Entries: 1
Quote:
Originally Posted by danny_66 View Post
Seems good speakers, someone reviewed them and found them a bit light in the bass.
Just add some 10" woofers and you'll have your bass
I have a sneaking suspicion that adding 10" woofers won't do much to alter the comparative differences in tonal balance of DAC's compared side by side using the same amp and speaker.
  Reply With Quote
Old 19th April 2015, 11:35 PM   #799
diyAudio Member
 
danny_66's Avatar
 
Join Date: Jun 2005
Location: Lierde
Correct, it's just for personal pleasure to feel the bass
__________________
My RefSpeaker
  Reply With Quote
Old 19th April 2015, 11:41 PM   #800
diyAudio Member
 
Join Date: Feb 2013
Location: Swindon, UK
DAC now all boxed up so time this evening to have a good listen to everything from 44-384k files, some original cd rips, some dsk, some up-sampled, all through usb input. Now favouring the newNOS for power, dynamics, transparency and soundstaging, and ability to lift out the smallest detail in the music - try Chesky's Ultimate Demo disk if you can. NOS may not measure as well as others with the scope, but with my ears.... Have fixed the Tag processor so can listen to CDs tomorrow through all Tag and compare with the new DAC, probably via Big Ben clock, which I know works very well.
  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 972 14th January 2017 06:31 PM
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 09:32 AM.


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