tda1541a sound signature - Page 3 - 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 13th June 2011, 07:12 AM   #21
diyAudio Member
 
Join Date: Apr 2007
Hello Thorsten

The OPA637 need a minimum gain of 5 but better with a gain of 10 to work good.

How can we use it in a IV amp ?

Thank

Bye

Gaetan

Last edited by gaetan8888; 13th June 2011 at 07:16 AM.
  Reply With Quote
Old 13th June 2011, 07:22 AM   #22
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by gaetan8888 View Post
The OPA637 need a minimum gain of 5 but better with a gain of 10 to work good.
That is not entirely correct. The OPA637 needs a NOISEGAIN of 5 (this is not neccesarily the same as the actual gain) and only at high freqiuencies.

Quote:
Originally Posted by gaetan8888 View Post
How do you manage to use it in IV amp ?
The usual way?

For a typical TDA1541 CD-Player from Philips/Marantz remove the 15-33pF compensation capacitor between pin 5 & 8 and connect 10nF (low inductance) from the inverting input to ground. The OPA637 will then work without any issues (as the noisegain is 5) and any additional problems caused by the very fast current steps from the DAC are mitigated.

While I derived this principle by my little old self, it was described before by Scott Wurcer in the Application notes for the AD797 somewhere, it was discussed several times here at DIYA, which is how I became of Scott's work on this.

Ciao T
  Reply With Quote
Old 13th June 2011, 07:23 AM   #23
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 98
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Quote:
Originally Posted by gaetan8888 View Post
How can we use it in a IV amp ?
Use what I call a 'gain stealing' network. A series RC to ground from - input raises the loop gain only at high frequencies whilst keeping it at unity for low DC offset. I see T suggests 10nF but does not mention any value for R. You'll want to watch the settling behaviour though on your scope - its easy to get the R and C values wrong.
__________________
It doesn't have to take the form of a conspiracy, rather a consensus... James H Kunstler
  Reply With Quote
Old 13th June 2011, 07:32 AM   #24
diyAudio Member
 
Join Date: Apr 2007
Hello Thorsten and abraxalito

Maby a simulation with LtSpice or Tina-Ti

Btw, is that higher value of cap for compensation will reduce the slew-rate of the 637 ?

You are both living in asia, I think, what time is it there ?

Here it's 3:30 am, I have to go to sleep.

Thank

Bye

Gaetan

Last edited by gaetan8888; 13th June 2011 at 07:35 AM.
  Reply With Quote
Old 13th June 2011, 07:37 AM   #25
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 98
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
3.30pm where I am.

You can try that LTSpice sim but in my experience the models aren't that close to reality, particularly in terms of dynamics. If you want good results you'll end up developing your own models and that takes longer than building and testing.

Nice job on the CD-77 btw Thorsten. I just wonder about one thing - the little labels on all but one of the ICs (not the TDA1541) in the Six Moons pic. Their purpose is?
__________________
It doesn't have to take the form of a conspiracy, rather a consensus... James H Kunstler
  Reply With Quote
Old 13th June 2011, 07:54 AM   #26
diyAudio Member
 
Join Date: Apr 2007
Hello

And about the slew-rate of the 637 with the higher value of that compensation cap ?

Thank

Bye

Gaetan

Last edited by gaetan8888; 13th June 2011 at 07:57 AM.
  Reply With Quote
Old 13th June 2011, 08:03 AM   #27
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 98
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
The comp cap Thorsten is talking about is the one needed to make a 5534 stable in unity gain. OPA637 has no such facility to compensate it for unity gain. With the external cap he's suggesting you don't lose any of the 637's better slew rate.
__________________
It doesn't have to take the form of a conspiracy, rather a consensus... James H Kunstler
  Reply With Quote
Old 13th June 2011, 08:17 AM   #28
diyAudio Member
 
Join Date: Apr 2007
Hello abraxalito and Thorsten

Since, in the Thorsten's example for those cd players, the opamp are use in inverting input, that 10nF cap from the inverting input to ground are just an input filtering to filter rf frequency ?

Thank

Bye

Gaetan

Last edited by gaetan8888; 13th June 2011 at 08:27 AM.
  Reply With Quote
Old 13th June 2011, 08:24 AM   #29
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 98
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Perhaps its best for Thorsten to answer that one. Myself I shy away from putting naked capacitors on the output of DACs - that's why you see my suggestion has a series resistor too. With the series R, the HF noise gain is clearly defined - so the R can be chosen to be one-quarter the value of the feedback resistor. Then the idea is not RF filtering rather opamp stability.
__________________
It doesn't have to take the form of a conspiracy, rather a consensus... James H Kunstler
  Reply With Quote
Old 13th June 2011, 08:48 AM   #30
diyAudio Member
 
Join Date: Oct 2005
Here you can find a schema for a ad811 i/v. Resister R2 is the key here. (All in dutch though). All inspired on Walt Jung's work.

Toon onderwerp - Philips DAC-960 modificatie • forum.zelfbouwaudio.nl
  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
FS : TDA1541A & TDA1541A S2 (Double Crown) Pocoyo Swap Meet 2 27th October 2010 03:26 AM
Sound signature differences between IRF510, 520, 530, and 540s? BoilermakerFan Solid State 17 6th August 2010 04:10 AM
MFA Lumi - possible to "un-darken" the sound signature? marknoir Tubes / Valves 16 23rd January 2007 04:02 AM
comments on my signature... roibm The Lounge 90 13th December 2004 07:03 PM
Crackling sound in right channel of TDA1541A DAC HeadSh0T Digital Source 3 9th December 2003 10:16 PM


New To Site? Need Help?

All times are GMT. The time now is 03:44 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