Digital Volume Control - Is It Good? - 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 2nd May 2004, 12:52 PM   #1
kspv is offline kspv  India
diyAudio Member
 
Join Date: Jan 2004
Location: Bangalore, India
Default Digital Volume Control - Is It Good?

I have heard that digital volume controls are inferior to analog volume controls, and that they reduce the quality of sound reproduction from CDs, by typically about 1 bit for every 6 dB reduction in volume, i.e., if the volume is reduced using a digital volume control from maximum to a level 6 dB lower, the 16 bit CD format will sound like a 15 bit one.

It is claimed that some companies like Wadia overcame this limitation by employing a conversion technology, which converts the 16 bit CD output to 21 bit, so that no noticeable reduction in quality occurs with reduction in volume using a digital volume control.

My questions are:

1.) Whether there is truth in the statement that digital volume controls reduce the quality of sound reproduction from CDs, by about 1 bit for every 6 dB reduction in volume?

2.) If it is true, why does it occur?

3.) Is using a CD player's built in volume control, for managing the overall system's (=integrated amplifier, subwoofer, speakers etc.) volume, bad?

I would be grateful for a reply.
  Reply With Quote
Old 3rd May 2004, 05:08 AM   #2
diyAudio Member
 
b-square's Avatar
 
Join Date: Feb 2004
Location: Seattle, WA
Yes, this is true in most cases. 6db is a factor of 2 change in volume (up or down), and each bit in a word is a factor of 2 change in range. Chop bits as digital voume controls typically do and you lose range.

CD players with variable outputs generally do the attenuation in the analog output section, not in the digital domain so there isn't the loss of range above.
  Reply With Quote
Old 4th May 2004, 03:27 AM   #3
diyAudio Member
 
Join Date: May 2004
Location: Ann Arbor, MI
Default Re: Digital Volume Control - Is It Good?

Quote:
Originally posted by kspv

My questions are:

1.) Whether there is truth in the statement that digital volume controls reduce the quality of sound reproduction from CDs, by about 1 bit for every 6 dB reduction in volume?

2.) If it is true, why does it occur?

3.) Is using a CD player's built in volume control, for managing the overall system's (=integrated amplifier, subwoofer, speakers etc.) volume, bad?

I would be grateful for a reply.
It is true that you lose a bit for every 6dB you attenuate. To reduce by 6dB is to cut it into half. The following explains how that equates to losing a bit: (2^n)/2 = 2^(n-1), where n is the number of bits and thus 2^n is the number of quantization levels. It is valid to increase the number of bits before applying the volume control. If a rate converter is being used, the output is most probably 24 bits anyway. Analog volume controls add their own degredation to the sound. There just isn't a neat word like "bit" that can be used to describe it. (Digital gets a bad rap sometimes in general for that reason.)

If you're using a source with digitally controlled volume coupled to a preamplifier (or intergrated amp) it is best to leave the source's volume at it's maximum level and use your analog pot.
  Reply With Quote
Old 4th May 2004, 09:48 AM   #4
diyAudio Member
 
Join Date: Nov 2002
Location: Essex, UK
Default Not to be confused with...

Beware that there are also digitally controlled resistor arrays that are used as volume controls. In this case, the signal is kept in the analogue domain and the digital part is used to route the signal through a series of resistors.
Have a look at the Dallas (Maxim) website for examples.
  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
digital volume control aardvarkash10 Tubes / Valves 11 10th December 2008 02:41 PM
Digital volume control maharadza Digital Source 9 8th April 2006 04:59 PM
Which VCA for Digital volume control gmphadte Analogue Source 8 30th September 2004 11:21 AM
Digital Volume control for in Car use dunderchief Digital Source 7 28th March 2004 12:08 AM


New To Site? Need Help?

All times are GMT. The time now is 02:18 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