Digital potentiometers why not more widespread... - 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 4th February 2004, 02:36 PM   #1
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Default Digital potentiometers why not more widespread...

Won't a digital pot be the ultimate in combination with a nice DAC?

Why are there no diy examples of these around?

Or are there?

Regards,
Bas
  Reply With Quote
Old 4th February 2004, 04:04 PM   #2
A 8 is offline A 8  Sweden
diyAudio Member
 
Join Date: Mar 2003
Location: Gothenburg
How do you figure it would be "ultimate" with a nice dac?
  Reply With Quote
Old 4th February 2004, 04:09 PM   #3
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Since I suppose attenuation in the digital domain would do less harm?
  Reply With Quote
Old 4th February 2004, 04:16 PM   #4
tiroth is offline tiroth  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
Edit: no, I disagree. Better to do only very small or no digital attenuation. Linearity will be much better.
  Reply With Quote
Old 4th February 2004, 04:17 PM   #5
diyAudio Member
 
Join Date: Sep 2002
Location: Sweden
Quote:
Originally posted by Bas Horneman
Since I suppose attenuation in the digital domain would do less harm?
You will need a DAC with a much better dynamic range then, so
it seems a bit questionable. It also assumes all sources are
digital in order to make sense.
  Reply With Quote
Old 4th February 2004, 04:17 PM   #6
tiroth is offline tiroth  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
If you want a digital pot just buy a sound blaster extigy and use the digital in and out.
  Reply With Quote
Old 4th February 2004, 04:18 PM   #7
A 8 is offline A 8  Sweden
diyAudio Member
 
Join Date: Mar 2003
Location: Gothenburg
Well, by doing it the digital domain you loose digital resolution and get more distorsion compared to analog attenuation on any level below 0dB.
  Reply With Quote
Old 5th February 2004, 07:08 AM   #8
August is offline August  Netherlands
diyAudio Member
 
Join Date: Jan 2004
Location: Utrecht
Although I have a digital attenuation on my dCS DAC, I never use it because it decreases the overall resolution audibly.

In my opinion adding a good preamp is better than driving a poweramp directly with a digital attenuation in the DAC. YMMV.
  Reply With Quote
Old 5th February 2004, 11:36 AM   #9
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Ok...that is settled .... digital attenuation sucks!

Thanks for all the contributions...

Cheers,
Bas
  Reply With Quote
Old 5th February 2004, 02:57 PM   #10
diyAudio Member
 
Join Date: Feb 2002
Quote:
Originally posted by Bas Horneman
Ok...that is settled .... digital attenuation sucks!

Thanks for all the contributions...

Cheers,
Bas

It may not be worth dredging up the details, but simply saying that digital attenuation sucks is way too simple.

It is probably true that for the 'typical' diy project, analog attenuation is easier/cheaper and likely to be better than digital attenuation. However, if you design and set up your system properly, digital attenuation *can* be essentially perfect. It's not all that easy to do, though.

Mathematically, digital attenuation is so close to perfect *provided you preserve 24 bit output* as to become an academic question - the distortion products will be 140dB down. However, in a real-world system the performance of the DAC is what limits the performance of a digital attenuation approach. Once you shift your signal down to where the the LSB of the input reaches the level of distortion and low-level nonlinearity of the DAC, you're to the point where you are distorting the signal.

With a modern high-performance DAC, you typically have noise/distortion/linearity performance down around -110 to -115 dB below full-scale. A 16 bit input from a CD has an inherent dynamic range of 96dB, so the first 10-15 or so dB of digital attenuation will be effectively perfect. HOWEVER, due gain mismatches between source and power amps, it is not unusual for a system to run with 5-10dB of attenuation even when playing loud, and 'typical' listening levels can easily be 20+dB down from full-scale, meaning that you are into the area where you are comprimising performance before you even start.

Of course, the noise floor and distortion profile of the power amp also come into things, but that doesn't change the fundamental issues, simply changes the boundary levels a bit.

So, all of this means that in most practical situations analog is the way to go. However, if you carefully design your system with the specific intent of being all-digital, you can build digital attenuation into the system without compromising it in any significant way.
  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
So I did try all those different potentiometers Peter Daniel Chip Amps 308 12th August 2009 02:29 PM
potentiometers mylar Parts 3 26th December 2001 08:54 PM
Potentiometers mylar Solid State 3 15th December 2001 05:04 PM


New To Site? Need Help?

All times are GMT. The time now is 10:54 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