ESS Sabre Reference DAC (8-channel) - Page 25 - 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 3rd March 2008, 08:45 PM   #241
diyAudio Member
 
Join Date: Oct 2006
Default Re: Digital Filter

Quote:
Originally posted by FuriousD
Dustin,

Can you bypass the digital filter and go straight into the DAC / Jitter reduction stage and use an external digital filter?

Cheers.

D.

What type of input did you have in mind. Simply a superfast "I2S" port that skips the data over the FIR? If this is what peple want, it will be easy to add in a future rev.


For the current chip, you could run the I2S data in at up to 351.5625kHz (thats 22.5MHz on the Data_Clk) and it should be fine. In that case you will want to have an 80MHz XI clock speed or so (just needs to be greater than 192*FS, so 67.5MHz, but adding a bit more speed helps the jitter blocker when LOTS of jitter is present)

Then is you dont like the Sharp OSF filter, you can choose the slow rolloff, this is actually a SINC responce filter that has been set such that the -3dB point is exactly 20k/44.1k or 0.4535FS. So if you run the data in at 151kHz and use the sloww rolloff filter, you will get a non-rippling filter with a -3dB point at 159kHz. IF this can work for you, then its already to go.


Thanks

Dustin
  Reply With Quote
Old 4th March 2008, 09:36 AM   #242
diyAudio Member
 
Join Date: Jun 2004
Location: UK
Default I2S Data width

Hi Dustin,

Am I correct in assuming that the 352kHz I2S input has data width of 24Bits? In which case i have to restrict my filtering to a 24-Bit data width which is not good. The advantage of the Texas part is that when you bypass the filter you have access to a 32-bit data width (Admittedly only at 192kHz but I can live with that).

I have a good idea what you have done after this, but the filter is the key to going from good sound to great sound. When I designed the concept of the Chord DAC64 filter it took a fairly unremarkable D2A concept and made it sound excellent.

I would love to be able to take an improved variant of that concept and couple it with the excellent performance of your modulator and DAC, but 24-bits is just not going to cut it.

If your filter has several stages, can we break in further down the line? at a wider bit width or faster rate?

Is there a work around on this? and if so what sort of time frame would this based upon.
  Reply With Quote
Old 4th March 2008, 09:46 AM   #243
Account Disabled
 
Join Date: Jan 2006
Location: whereisit
What's the use of 32 bits? There's no audio DAC on the planet linear to the full 24 bits even, and 20 bits alone more than covers the ear's audible dynamic range from threshold of hearing to threshold of pain.
  Reply With Quote
Old 4th March 2008, 10:04 AM   #244
diyAudio Member
 
Join Date: Jun 2004
Location: UK
Quote:
What's the use of 32 bits? There's no audio DAC on the planet linear to the full 24 bits even, and 20 bits alone more than covers the ear's audible dynamic range from threshold of hearing to threshold of pain.
The ESS DAC itself uses a user selectable bit width quantiser. Normally set around 6-Bits. This is the actual DAC resolution. So Delta Sigma modulation is being used to sacrifice out of band noise perfromance in favour of increasing in band SNR.

If you read the datasheet for the ESS part you will see that it has an internal data path of 48-Bits. You will note that the DAC64 has an internal data path of 64-Bits. There is a good reason for this.

Whilst 24-input bits gives a theoretical DNR of 144dB, if the data path has out of band components at -144dB prior to the actual DAC stage internally, then the massive out of band gain of the modulator will amplify these components up to a level that is very much significant.

24-Bit input data x 24 bit tap coefficients in the filter = 48-Bit result. To input that back into a 24-bit input, you would need to dither or just truncate it back down to 24-Bits and that is where the problems begin.
  Reply With Quote
Old 4th March 2008, 10:07 AM   #245
Account Disabled
 
Join Date: Jan 2006
Location: whereisit
So what's wrong with dithering? If whatever error is out of band, why would it be a problem, regardless how much amplified?
  Reply With Quote
Old 4th March 2008, 11:21 AM   #246
diyAudio Member
 
Join Date: Nov 2005
Location: Greenwich, London, UK
Default Re: I2S Data width

Quote:
Originally posted by FuriousD
Hi Dustin,

Am I correct in assuming that the 352kHz I2S input has data width of 24Bits? In which case i have to restrict my filtering to a 24-Bit data width which is not good. The advantage of the Texas part is that when you bypass the filter you have access to a 32-bit data width (Admittedly only at 192kHz but I can live with that).

I have a good idea what you have done after this, but the filter is the key to going from good sound to great sound.
When I designed the concept of the Chord DAC64 filter it took a fairly unremarkable D2A concept and made it sound excellent.

I would love to be able to take an improved variant of that concept and couple it with the excellent performance of your modulator and DAC, but 24-bits is just not going to cut it.

If your filter has several stages, can we break in further down the line? at a wider bit width or faster rate?

Is there a work around on this? and if so what sort of time frame would this based upon.
The DAC64's filter is a Watts Transient Aligned filter (WTA Filter). Are you Rob Watts?

If not, you must be Mark Dixon?
  Reply With Quote
Old 4th March 2008, 11:23 AM   #247
Account Disabled
 
Join Date: Jan 2006
Location: whereisit
Default Re: Re: I2S Data width

Quote:
Originally posted by InfiniteGain
The DAC64's filter is a Watts Transient Aligned filter (WTA Filter).
Hmm, there was a discussion on that at Bruno Putzeys' forum.

Anyway, back to topic please.
  Reply With Quote
Old 4th March 2008, 11:41 AM   #248
diyAudio Member
 
Join Date: Nov 2005
Location: Greenwich, London, UK
Default Re: Re: Re: I2S Data width

Quote:
Originally posted by abzug

Hmm, there was a discussion on that at Bruno Putzeys' forum.

Anyway, back to topic please.

I started this thread. I believe the topic is specifically based around my initial question of how us DIYers get our hands on one or two chips in low volume, and if anybody had already used it and could give feedback on how it sounds given the impressive specs.

Those questions remains unanswered. It seems the chip is really still a prototype and is yet to undergo a few revisions. There has only been technical questions and answers about certain aspects of the chips design implementation and some interfacing options. They only come in handy if I can get hold of it to do something with it.

  Reply With Quote
Old 4th March 2008, 11:49 AM   #249
Sheriff is offline Sheriff  United Kingdom
diyAudio Member
 
Sheriff's Avatar
 
Join Date: Feb 2003
Location: England
Send a message via Skype™ to Sheriff
If i remember rightly , almost all of the DAC 64 work was completed before Mark Dixon joined Chord.

The DAC64 started out life as an AV processor.
  Reply With Quote
Old 4th March 2008, 12:38 PM   #250
diyAudio Member
 
Join Date: Nov 2005
Location: Greenwich, London, UK
Quote:
Originally posted by Sheriff
If i remember rightly , almost all of the DAC 64 work was completed before Mark Dixon joined Chord.

The DAC64 started out life as an AV processor.
So you would be Mike Gregory then?

Is there anybody on this thread other than myself who does not work for a commercial electronics/audio firm and/or have an electronics degree or doctorate? I am feeling distinctly out of place!

  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 03:30 PM.


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