Using the AD844 as an I/V - Page 8 - 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 15th January 2013, 02:33 AM   #71
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
dont have time now, havent read them for years. i'll look into that when I refresh on his articles soon, looking to do a layout of the recent shunt version.

but another point I will make is that Walt is not the only one to have had trouble with AD797 at low or unity gain. its one of the reasons its been labelled as a somewhat cranky opamp. maybe its simply that running at low or unity gain accentuates issues with problem PCB layouts that would otherwise be fixed with higher gain.
  Reply With Quote
Old 15th January 2013, 02:36 AM   #72
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: 109
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Yes Walt had stability issues, that's what Jan was talking about, but he didn't abandon the AD797 in that design until he came up against RF issues. Only then did he chuck out the part in favour of AD825.
__________________
Seek not the favour of the multitude...rather the testimony of few. And number not voices, but weigh them. - Kant
The capacity for impartial observation is commonly called 'cynicism' by those who lack it.
  Reply With Quote
Old 15th January 2013, 02:43 AM   #73
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
Quote:
Originally Posted by abraxalito View Post
Yes Walt had stability issues, that's what Jan was talking about, but he didn't abandon the AD797 in that design until he came up against RF issues. Only then did he chuck out the part in favour of AD825.
huh? now your just being silly, just because there was another issue in addition to the stability that was the final straw, doesnt mean that stability was not an issue, or even the major issue. I'm not saying it was or wasnt, its been too long for me to remember, but why seemingly argue that stability was not an issue?

anyway thanks for the reminder, its always good re-reading articles from these guys as experience grows, further things usually click into place.
  Reply With Quote
Old 15th January 2013, 03:02 AM   #74
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: 109
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Stability wasn't the issue that killed the AD797 in that design - Walt was happy that it was resolved enough to continue to keep the AD797 in that reg design. You think Mr Jung would run with a design that he didn't consider good enough to publish and recommend others to copy when they needed a reg? To me that says stability wasn't a significant issue in that design.
__________________
Seek not the favour of the multitude...rather the testimony of few. And number not voices, but weigh them. - Kant
The capacity for impartial observation is commonly called 'cynicism' by those who lack it.
  Reply With Quote
Old 15th January 2013, 04:23 AM   #75
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
Looks like George is happy with Zin = 65 ohm for his 1704 after all.
But I have the SEN, and the AD844.



Zen -> Cen -> Sen, evolution of a minimalistic IV Converter


Patrick
__________________
xen-audio.com

Last edited by EUVL; 15th January 2013 at 04:36 AM.
  Reply With Quote
Old 15th January 2013, 04:27 AM   #76
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
yeah its too high for ESS or I would try it
  Reply With Quote
Old 15th January 2013, 04:38 AM   #77
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
Too high for me even for the 1704.
But I know some people has tried the 1704 with 22R passive IV followed by tube stage.
So maybe 3x 844 in parallel will do ....

I still prefer my SEN, by far. But then I am biased.


Patrick
__________________
xen-audio.com
  Reply With Quote
Old 15th January 2013, 07:30 AM   #78
diyAudio Member
 
georgehifi's Avatar
 
Join Date: Sep 2003
Location: Manly Australia (Jewel of the Pacific)
Send a message via MSN to georgehifi
Input Z for the AD844 is 50ohm typical, , and happy with it is an understatment, it's a game changer as far as being compared to the normal highend opamps with feedback.
This AD844 when used without global feedback and even with it's own output buffer has made me feel that all other opamp based I/V's are seriously flawed, and I don't think I have it at it's best yet either.
Someone said it needs to be biased higher than it's quiescent current of 6.5mA, but correct me if I'm wrong but the PCM1704 can only give +-1.2mA at full swing 0dbf.
But maybe they meant with the TDA1541 which gives out a much higher than that.

Cheers George
__________________
Avatar : Production Lightspeed Attenuator
www.lightspeedattenuator.com
  Reply With Quote
Old 15th January 2013, 09:51 AM   #79
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
We have eventually built the AD844 discrete using BC550 / BC560 (see the link above) ourselves to get to the low Zin of <10R.
I still prefer the SEN in an A-B test.


Patrick
__________________
xen-audio.com
  Reply With Quote
Old 15th January 2013, 12:54 PM   #80
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
What about this IV for PCM1704?

Click the image to open in full size.
  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
AD844 as a common base stage in the I/V converter Pedja Digital Source 42 25th March 2013 08:56 AM
WTB AD844 Opamps apassgear Swap Meet 6 31st January 2007 03:57 PM


New To Site? Need Help?

All times are GMT. The time now is 10:30 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