Building the ultimate NOS DAC using TDA1541A - Page 41 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Line Level

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 22nd June 2006, 04:47 AM   #401
diyAudio Member
 
-ecdesigns-'s Avatar
 
Join Date: May 2006
Hi maxlorenz,

No, I'm not angry [post#375]

I just wanted to indicate the errors produced by NOS-DAC's and the octal D-I DAC are present, but wanted to put them into perspective. By over-emphasizing problems there is no point in designing anything as nothing will ever be perfect enough. One theory fill follow the other, with the end result a NO-DAC.

I will take your wise advice,

As far as I am concerned, the octal D-I DAC also transmits the soul of music. In my humble opinion this is mainly caused by both phase linearity and harmonic balancing using the mixed mode. The Direct Interpolation reduces harmonics amplitude when compared to the standard NOS-DAC. I already invited one DIYaudio member for a listening session.

Resting from time to time is very difficult for me, I have been working for over 15 years now without a holliday. Guess that makes me kind of a workaholic .
  Reply With Quote
Old 22nd June 2006, 08:19 AM   #402
diyAudio Member
 
-ecdesigns-'s Avatar
 
Join Date: May 2006
Default Some octal D-I DAC oscillograms

Hi all,

I added some oscillograms that show comparison between signals generated by a standard NOS-DAC and octal D-I DAC, both DAC's get the same SPDIF input signal, this might put things in perspective. Oscillograms also show both DAC output signals run nicely in phase.

Photo top left, shows how the octal D-I DAC smoothes a course stepped sinewave

Photo top right, shows what is still recovered with very few steps.

Photo bottom left, shows a 500Hz sinewave greatly magnified, notice the gained resolution

Photo bottom right, shows a 1 KHz squarewave, notice the flat responce and the steps on the transient

So the squarewave shaped signals with mainly odd harmonics, are converted to a more sawtooth / triangle shaped signal with more even harmonics. Soundwise even harmonic distortion has a less negative effect on sound quality then odd harmonic distortion.

The major harmonics are caused by the difference between a pure sinewave and the stepped approximation. The harmonics amplitude is in relation with the amplitude of the error signal. By generating smoother stepped sinewave signals, the amplitude of the error signal drops accordingly. The harmonics are still there, but their amplitude has been lowered. By the higher virtual sample frequency, harmonics are shifted up the spectrum, so interference in the audio spectrum is reduced

One could use a (Bessel) filter to attenuate these residual harmonics, if desired, they are already attenuated by bandwith limiting in the amplifier
Attached Images
File Type: jpg oscdac1.jpg (83.2 KB, 1692 views)
  Reply With Quote
Old 22nd June 2006, 10:46 AM   #403
diyAudio Member
 
Bernhard's Avatar
 
Join Date: Apr 2002
Location: Munich
Quote:
Originally posted by poobah
I
the graph would not post here well.

Do you think it would hurt anybody ?
  Reply With Quote
Old 22nd June 2006, 11:00 AM   #404
diyAudio Member
 
Bernhard's Avatar
 
Join Date: Apr 2002
Location: Munich
About the possible reduction of nonlinearity:

I did not look at the schematics but if it is linear interpolation of 8 DACs, it should be at the start of a new original sample:

1 DAC carries current of new sample & 7 DACs carry current of previous sample -> 2 DACs carry current of new sample & 6 DACs carry current of previous sample -> 3 DACs carry current of new sample & 5 DACs carry current of previous sample -> 4 DACs carry current of new sample & 4 DACs carry current of previous sample -> 5 DACs carry current of new sample & 3 DACs carry current of previous sample -> 6 DACs carry current of new sample & 2 DACs carry current of previous sample -> 7 DACs carry current of new sample & 1 DAC carries current of previous sample -> 8 DACs carry current of new sample & 0 DACs carry current of previous sample -> starts next original sample...

So there are 8 different combinations of paralleled DACs inside one original sample.

That could be even more beneficial than just paralleling.

Please correct me if I'm wrong.
  Reply With Quote
Old 22nd June 2006, 11:01 AM   #405
diyAudio Member
 
Join Date: Jun 2002
Location: Italy
I think so ...
  Reply With Quote
Old 22nd June 2006, 11:23 AM   #406
diyAudio Member
 
Bernhard's Avatar
 
Join Date: Apr 2002
Location: Munich
Quote:
Originally posted by rfbrw


...we don't want no no-sayers here in town.

And no clueless photographers either.
Nice to hear that you share my opinion about the notorious no-sayers

Any clueless photographers around ?
  Reply With Quote
Old 22nd June 2006, 01:06 PM   #407
diyAudio Member
 
Join Date: Oct 2001
Location: .
Quote:
Originally posted by Bernhard
About the possible reduction of nonlinearity:

I did not look at the schematics but if it is linear interpolation of 8 DACs, it should be at the start of a new original sample:

1 DAC carries current of new sample & 7 DACs carry current of previous sample -> 2 DACs carry current of new sample & 6 DACs carry current of previous sample -> 3 DACs carry current of new sample & 5 DACs carry current of previous sample -> 4 DACs carry current of new sample & 4 DACs carry current of previous sample -> 5 DACs carry current of new sample & 3 DACs carry current of previous sample -> 6 DACs carry current of new sample & 2 DACs carry current of previous sample -> 7 DACs carry current of new sample & 1 DAC carries current of previous sample -> 8 DACs carry current of new sample & 0 DACs carry current of previous sample -> starts next original sample...

So there are 8 different combinations of paralleled DACs inside one original sample.

That could be even more beneficial than just paralleling.

Please correct me if I'm wrong.

You are wrong. All samples are 'original' and nothing is in parallel.
  Reply With Quote
Old 22nd June 2006, 01:11 PM   #408
diyAudio Member
 
Join Date: Oct 2001
Location: .
Quote:
Originally posted by Bernhard


Nice to hear that you share my opinion about the notorious no-sayers

Can't say I do, not that it matters much. You'll talk a lot and measure a lot but it will be a cold day in hell when you actually make anything.
  Reply With Quote
Old 22nd June 2006, 02:27 PM   #409
diyAudio Member
 
Bernhard's Avatar
 
Join Date: Apr 2002
Location: Munich
Quote:
Originally posted by rfbrw



You are wrong. All samples are 'original' and nothing is in parallel.

Ok, samples are original, but only on the digital side.
The DACs get them with different delays.
The delays are < one sample so the samples overlap and that is where the DACs are parallel.
On the analog side x DAC-currents from a previous sample are added to y DAC-currents from the next sample, and the I/V does see it as a new & wrong sample.


Your post #408 is not worth a reply.
  Reply With Quote
Old 22nd June 2006, 03:19 PM   #410
diyAudio Member
 
Join Date: Oct 2004
I agree with Bernhard, a DACs output is held until the next sample value is reproduced. So all the DAC outputs, at any given time, will be providing a current - so they are all summed as they are connected in parallel.

rfbrw, I think you are unreasonable to comment like you did. I am incredibly distracted, and I rarely make much kit at the moment. Everybody's commitments and distractions elsewhere in life impact this. I envy you as you obviously have more time than I (and perhaps Bernhard) to craft things. However, there is nothing wrong at all with theoretical discussion, and sensible measurement. They have their places.

This is a great thread. Please, lets not spoil it!

Cheers,
Phil
  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



New To Site? Need Help?

All times are GMT. The time now is 01:07 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2