Noise in DAC - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, 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 15th April 2004, 09:48 PM   #1
diyAudio Member
 
Bernhard's Avatar
 
Join Date: Apr 2002
Location: Munich
Question Noise in DAC

Hi,

Story:

Still my CD304 seems to be a very little bit smoother and darker, compared to the CD880.
Unfortunately the CD304 refused to play the test CD rom.
Today I cleaned the laser and it worked, so I was expecting different harmonic spectrum.

I plugged the TDA chip from 880 in 304. Test signal -60dB.

On one channel ( lower graph ) it is really a little different, 5 dB worse K2.

But other channel ( upper graph ) has noise that hides all harmonics.

Usually the noise is - 68dB.

This noise in the faulty channel is -48dB close to 1 kHz and goes down to -58dB @ 10kHz.

I have no idea where such noise may come from.

It is not noticeable when playing normal music, only visible with the analyzer.

If this noise makes sound nicer because of hiding harmonics, I would like to know how to achieve it

Is noise preferred over distortion by human hearing ?
Attached Images
File Type: jpg noise.jpg (66.2 KB, 278 views)
  Reply With Quote
Old 15th April 2004, 10:05 PM   #2
diyAudio Member
 
johnferrier's Avatar
 
Join Date: Sep 2003
Location: WA
Guess my thinking is that while there is disagreement about what the distortion profile should be like, there is agreement that noise should be low. However, everything is relative and it's really is up to your ears and mind.


JF
  Reply With Quote
Old 15th April 2004, 10:11 PM   #3
diyAudio Member
 
Bernhard's Avatar
 
Join Date: Apr 2002
Location: Munich
Quote:
Originally posted by johnferrier
Guess my thinking is that while there is disagreement about what the distortion profile should be like, there is agreement that noise should be low. However, everything is relative and it's really is up to your ears and mind.


JF
This noise shows up with the -60dB test signal, with 0dB signal of course it will be much smaller.
  Reply With Quote
Old 15th April 2004, 10:31 PM   #4
diyAudio Moderator Emeritus
 
jean-paul's Avatar
 
Join Date: Sep 2002
Location: Germany
Maybe a simple explanation is that the TDA is EOL ? Also measuring with -60dB is asking much from second generation chips that have had a life of several years of service and much power on/off sequences. As I told you before TDA's can fail ( the non A versions more than A versions ) which ends in one channel distorting or even no signal at all.

If it is only one of your collection I would not think much about it and try another one.

Quote:
It is not noticeable when playing normal music, only visible with the analyzer.
It will be noticeable in time. The results you've measured definitely have influence on the sonical results, the human ear is sensitive to low level signals. Try listening with different material.
I think results will differ at power up and after 15/20 minutes warm up.
__________________
It's only audio. Official member of the Norske Brillegeit Gang.
  Reply With Quote
Old 15th April 2004, 11:17 PM   #5
diyAudio Member
 
Bernhard's Avatar
 
Join Date: Apr 2002
Location: Munich
Quote:
Originally posted by jean-paul
Maybe a simple explanation is that the TDA is EOL ? Also measuring with -60dB is asking much from second generation chips that have had a life of several years of service and much power on/off sequences. As I told you before TDA's can fail ( the non A versions more than A versions ) which ends in one channel distorting or even no signal at all.


Quote:
I plugged the TDA chip from 880 in 304. Test signal -60dB.
The chip is 100% ok.

I have re-checked in CD880.

Maybe one of the 14 decoupling caps on the CD30 board is bad soldered or dead.
  Reply With Quote
Old 21st April 2004, 08:22 PM   #6
diyAudio Member
 
Join Date: Jan 2004
Location: Cape Town
Quote:
Is noise preferred over distortion by human hearing ?
Yes, it is.
That is why dithering and noise-shaping techniques on digital signals can sound so good. They reduce harmonic distortion at the cost of increased noise. The noise masks the harmonics and is generally inaudible under the signal. Basically our brains are very used to hearing a level of white noise, but harmonic distortions sounds unnatural.
You might find this interesting:
http://recpit.prosoundweb.com/viewtopic.php?t=1284
  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
Low noise transistor and noise figure Real_Macgyver Solid State 28 27th July 2012 09:42 AM
Hum and Noise with Ono rsbay Pass Labs 0 26th February 2006 12:51 PM
NOISE - RFI and EMI jackinnj Everything Else 9 26th February 2005 01:01 PM
Noise Bukitoo Analogue Source 2 17th March 2004 02:37 PM
DSP and DAC noise nFORCE Digital Source 4 29th April 2003 03:18 PM


New To Site? Need Help?

All times are GMT. The time now is 02:28 PM.


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