Upgrading the output components in a prosumer dac - Page 2 - 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 29th September 2010, 10:09 PM   #11
DougL is offline DougL  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Wheaton IL.
Blog Entries: 30
Quote:
Would I be able to directly connect the transformers to the dac outputs
Yes, you can attach the transformer primaries directly to the transformer, as long as the voltage on both is roughly the same. In your application, I would not ground the center tap.

HTH

Doug
__________________
Scienta sine ars nihil est - Science without Art is nothing. (Implies the converse as well)
Mater tua criceta fuit, et pater tuo redoluit bacarum sambucus
  Reply With Quote
Old 2nd October 2010, 06:52 AM   #12
diyAudio Member
 
Join Date: Dec 2007
I may have to draw a diagram. The codec chip has 8 output channels, so I guess I would be willing to experiment on a set of them. If I manage to get the drawing right, would anybody here be willing to help take a look at it and suggest what sort of modifications might be advisable?
  Reply With Quote
Old 3rd October 2010, 04:55 AM   #13
dangus is offline dangus  Canada
diyAudio Member
 
Join Date: May 2004
Location: Vancouver Island
How about adding servos to null out the DC offset? Take a look at Walt Jung's audio opamp articles.
  Reply With Quote
Old 3rd October 2010, 05:51 AM   #14
diyAudio Member
 
Join Date: Dec 2007
I'll try to get the diagram together, there is a lot of stuff going on and they may already be doing that on the board. I'll try to get a diagram up in the next few days.
  Reply With Quote
Old 9th October 2010, 04:59 AM   #15
diyAudio Member
 
Join Date: Dec 2007
Alright, the pcb is too complicated to figure out. Its many layered and there are no schematics anywhere. Given the options, it seems like using a pair of transformers coupled to the dac outputs are the way to go.

Before I commit to this experiment, I want to be sure that there won't be a problem with the output levels going on. Attached is a diagram from the datasheet of the dac that shows the output levels. There is a 2.7v offset. With that issue, can I still use the transformers directly connected to it because the offset is identical and thus the transformer would effectively block the DC? Or does this mean that I need to correct the 2.7v offset first before I can use a transformer?

The other part I need help with is about the transformer itself. The dac datasheet says:

dac output impedance: 150 ohms
AC load resistance: 3K ohms
load capacitance max: 30 pF

So from that I know that I need a relatively high impedance input for the transformer, which is why the 10k input was suggested. Now the part I'm concerned about is that in the suggested 10k:10k. The second 10k listed is the load impedance correct? Does that mean that the output impedance is 10k and thus I would need a 100k input impedance on the receiving device, or does it simply mean that it expects a 10k or greater input impedance for that other device?

I think that about covers it. The edcors seem like they may be a decent budget way to try this out, anything to watch out for with them? Thanks.
Attached Images
File Type: jpg cs42428_outputdiagram.jpg (28.3 KB, 61 views)
  Reply With Quote
Old 9th October 2010, 05:50 AM   #16
DougL is offline DougL  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Wheaton IL.
Blog Entries: 30
Quote:
Before I commit to this experiment, I want to be sure that there won't be a problem with the output levels going on. Attached is a diagram from the datasheet of the dac that shows the output levels. There is a 2.7v offset. With that issue, can I still use the transformers directly connected to it because the offset is identical and thus the transformer would effectively block the DC? Or does this mean that I need to correct the 2.7v offset first before I can use a transformer?
As long as you do not DC ground the center tap on the input side, the 2.7 volts will not cause a current and everything will work.
Quote:
So from that I know that I need a relatively high impedance input for the transformer, which is why the 10k input was suggested. Now the part I'm concerned about is that in the suggested 10k:10k. The second 10k listed is the load impedance correct? Does that mean that the output impedance is 10k and thus I would need a 100k input impedance on the receiving device, or does it simply mean that it expects a 10k or greater input impedance for that other device?
Transformers do not have an impedance. On a 1:1 transformer, it reflects the output Z of the Dac, and reflects the load resistor.
I like to think of it this way, the output Z of the drivers should be less than 10K and the next stage should be 10K or higher.
__________________
Scienta sine ars nihil est - Science without Art is nothing. (Implies the converse as well)
Mater tua criceta fuit, et pater tuo redoluit bacarum sambucus
  Reply With Quote
Old 10th October 2010, 06:57 PM   #17
diyAudio Member
 
Join Date: Dec 2007
Thanks for setting that straight

I have just noticed an issue with the dac outputs, so I'm going to make another thread and before I try the transformers I'd like to correct the issue. Please check that thread out!
  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
Upgrading crossover components, any advices? Ageve Multi-Way 5 15th April 2008 12:21 PM
upgrading components on Bush CD790 Simpleton Digital Source 5 16th August 2005 07:20 PM
Upgrading crossovers with Solen components & a small problem. KevinLee Multi-Way 15 20th June 2003 12:23 AM


New To Site? Need Help?

All times are GMT. The time now is 04:45 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