Simulation of I/U (I/V) converter versions for TI PCM R2R DAC's (e.g. PCM1704) ?" - 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 20th July 2009, 11:15 AM   #1
diyAudio Member
 
tiefbassuebertr's Avatar
 
Join Date: Jul 2005
Location: D-55629 Schwarzerden
Default Simulation of I/U (I/V) converter versions for TI PCM R2R DAC's (e.g. PCM1704) ?"

For check out and compare of different I/U circuit topologies by simulation I cannot use the generator with internal resistance of 0 ohms. What I must do for prepare to get exactly simulation results ?

Best thanks for your advices.
  Reply With Quote
Old 20th July 2009, 11:47 AM   #2
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
Use a current source, it should be there in the simulator.

I use LT spice and it is called Current
  Reply With Quote
Old 24th July 2009, 06:40 PM   #3
Hurtig is offline Hurtig  Denmark
diyAudio Member
 
Join Date: Feb 2005
Location: Denmark - Århus
Sorry to correct you Sonnya, but using a current source will NOT simulate a true PCM1704 or similiar output.
Check page 2 in the PCM1704 datasheet: PCM1704 Datasheet
Find the "Analog Output" section... Here it says that the output current is 1.2mA and the output impedance is 1kohm. Since this is a "current generator", the output impedance should med simulated by using a 1.2mA current source in parallel with a 1kohm resistor.

By doing this, you will notice why the input impedance of the I/V converter is so critical. If you have a 1kohm input impedance, only half of the signal strength will go into the I/V converter, while the rest is blown away inside the PCM1704.
But it gets worse. Since the input impedance will most likely be non-linear, you will have a non-linear transfer between the PCM1704 and the I/V converter. The lower the input impedance, the less critical the non-linarities of the impedance will be. The difference in signal-energy transferred will be less, since almost all the energy is transferred at low impedances.
This really is one of the main reasons why you must ALWAYS use a low impedance I/V converter for critical applications.

The other reason is, that a high impedance input will result in voltage changes along with the music signal. And that will cause non-linarities inside the DAC-circuit.

So again! Use a low impedance input I/V-converter, and remember the paralell resistor at the current source when simulating.
  Reply With Quote
Old 24th July 2009, 09:54 PM   #4
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
well. If you have read the original thread. You would have seen that i already have addressed the non lin. problem. Once again too hurtig
  Reply With Quote
Old 25th July 2009, 11:06 AM   #5
Hurtig is offline Hurtig  Denmark
diyAudio Member
 
Join Date: Feb 2005
Location: Denmark - Århus
The "Original Thread". Where is that????

I just replied to the discussion in this thread....
  Reply With Quote
Old 27th July 2009, 09:37 PM   #6
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
Sorry it is my fault. I thought i have seen the link in the top of this thread.

Here is the link

http://www.diyaudio.com/forums/showt...33#post1882633
  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
Who has the "best" PCM1704 DIY board/design/kit?? bear Digital Source 26 21st September 2012 01:43 AM
Aleph 4 - Simulation Results from "Circuitmaker" tiefbassuebertr Pass Labs 0 18th July 2009 12:53 AM
Do they make 1/4" balanced pro jack to RCA converter plugs? darkmoebius Parts 7 17th July 2005 06:52 AM
can one buy a head phone "wireless" converter cord? joywrex Parts 0 14th June 2003 05:41 PM
Real "cool" R-Theta heatsink simulation Gabster Pass Labs 26 15th April 2002 05:14 AM


New To Site? Need Help?

All times are GMT. The time now is 04:23 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