I/V using opamps - Page 7 - 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 23rd December 2012, 12:25 PM   #61
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
You could try the LM4562 which is available in SMD. I like the OPA2604 when implemented correctly so either something is going amiss or you just don't like the subtleties of the OPA2604's presentation.

Swapping Op-Amps... you have checked to see it's stable haven't you ?

Also, try attaching your picture directly

To add a photo, files or non standard files.

First click "go advanced" in the box below the "quick reply" message box. Doesn't matter if you decide half way through a message to do that, it carries it foward.

Then click "Manage attachements". Maximise the new Window so that you can see all the text.

Click browse in the first box at the top and find your picture. Repeat for any more pictures.
Click upload... a message appears "uploading"
When complete the files will show as being attached. Now click the small text that says "close this window"

The pictures should now be attached and when you submit your post they will appear.

Make sure your pics aren't too big, a couple of 100k is plenty, and many members object when they are massive and it alters the margins
It tells you in the attachments window what max sizes are allowed.


If you want to attach a file that has a non standard format for example excel, circuit simulation etc then try putting the files in a zipped folder and attaching that.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 23rd December 2012, 12:34 PM   #62
Trident is offline Trident  Spain
diyAudio Member
 
Trident's Avatar
 
Join Date: Dec 2009
Location: La Coruña (Spain)
Mooly,

Thank you very much for your advice to add images, is the first image you insert.

If the assembly is stable. Not the first time I ride the OPA2604 with good results, but this time it was not so.

In the output stage OPA275've ridden. it also has a good sound.
  Reply With Quote
Old 24th December 2012, 12:52 PM   #63
diyAudio Member
 
Join Date: Oct 2009
Location: Brunei
Quote:
Originally Posted by abraxalito View Post
Definitely worth trying a filter, even with TDA1541A. Its definitely also worth bringing up the droopy top end by some means. You could do that by adding on two more TDA1541As (if you're feeling fairly rich) and feeding them with an HEF4517 delay line to create a 3 tap FIR filter. Thorsten also says undoing the droop is definitely worthwhile, I think he does it by some passive LC circuit, though not sure of the details.
Actually i have a small collection of tda1541a chips, so i could try the 3tap fir filter. But that seems a long term project.

For the time being, i will try the filter (not the amplification) stage as pictured here. Thorsten's tube Stage for TDA1541A

What do you think of that one? Seems a lot less complex than the one you described earlier (7th order elliptical).

What is your view on the adverse effects on phase?
__________________
--------
TDA1541a-S2 / 6072a / MediaplayerDac -- Michell Gyrodec -- Aikido Preamp -- Pass F5 -- Audio Physic Tempo 2SE -- Yamamura Cabling
  Reply With Quote
Old 24th December 2012, 01:04 PM   #64
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: 96
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Well I've tried caps (in this schematic, C2) to ground and haven't liked the sound. But then I've not tried with TDA1541A. The filter is only first order and you do need a very clean ground to connect that cap to - unfortunately its driven by a high speed DAC and hence the routing of that ground is crucial. I doubt I ever got it right So while it will correct the droop with that LC tank (which my elliptic doesn't) it won't filter glitches very severely. Which is probably fine when you have a valve following it, but not so good for SS.

As for phase effects, subjectively haven't noticed any even though the phase performance of my elliptic filter isn't so hot at the top end. Lots of group delay above 10k or so. I read somewhere that to be audible the group delay around 10k needs to be something like 2mS, I think my filter gives less than this.
__________________
It doesn't have to take the form of a conspiracy, rather a consensus... James H Kunstler
  Reply With Quote
Old 24th December 2012, 01:44 PM   #65
diyAudio Member
 
Join Date: Oct 2009
Location: Brunei
i am runnig my dac now non-oversampling without any filtering. Quite happy with it, but i do hear a recessed top-end. This would probably for me be the objective of adding a filter: compensate the roll-off towards 20khz.

The elliptical filter, and its steep cutoff would be more aimed at the (anti)aliasing effects beyond 20khz i would presume.
__________________
--------
TDA1541a-S2 / 6072a / MediaplayerDac -- Michell Gyrodec -- Aikido Preamp -- Pass F5 -- Audio Physic Tempo 2SE -- Yamamura Cabling
  Reply With Quote
Old 24th December 2012, 01:52 PM   #66
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: 96
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
The purpose is two-fold, yes definitely to attenuate the image frequencies - it has better than -50dB stop band. But I reckon (still have to simulate this to verify the hypothesis) that even a totally glitch-free DAC generates broadband noise just by virtue of having a finite settling time between output states. The filter severely limits the extent of this noise - the subjective effect being a considerable soundstage depth improvement (on TDA1545A).
__________________
It doesn't have to take the form of a conspiracy, rather a consensus... James H Kunstler
  Reply With Quote
Old 24th December 2012, 04:30 PM   #67
Trident is offline Trident  Spain
diyAudio Member
 
Trident's Avatar
 
Join Date: Dec 2009
Location: La Coruña (Spain)
Hi Mooly,

I have checked with my oscilloscope, the output signal at 1KHz-20dB in the OPA2604, and shows no oscillation, apparently.

I compared with a second unit SL-P999, oscillograms and levels are identical in both units.

But no the sound.
Attached Images
File Type: jpg 20121224_141546.jpg (287.9 KB, 229 views)
  Reply With Quote
Old 24th December 2012, 04:43 PM   #68
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
That looks OK, but you don't like the sound

All you can do is try other alternatives. The good thing is that you can identify differences and know what "kind" of sound you want. My experience of the OPA2604 has been good and so to the OPA2134.

I don't know what else to suggest to you. Maybe the "Excaliber" TLE2072 which based on the TL072 but with high drive ability.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 24th December 2012, 05:21 PM   #69
Trident is offline Trident  Spain
diyAudio Member
 
Trident's Avatar
 
Join Date: Dec 2009
Location: La Coruña (Spain)
Thanks Mooly

I've always had good experiences with the OPA2604, and has been my first choice. Maybe the problem is in the coupling between the two operational bridge, is a very common mounting Technics players with high-end linear DAC, I have not seen in other manufacturers.
Attached Images
File Type: jpg technics_sl-p999.jpg (86.9 KB, 222 views)
  Reply With Quote
Old 24th December 2012, 05:38 PM   #70
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
I've never seen that configuration before used with opamps. Its very like the Class AA ? Technics and Aubrey Sandmans Class S power amps.

I looked up the data sheet on the M5238 and its a high current output device which makes sense given the low values of "R" in the bridge.

The TLE2072 I mentioned has an 80 ma drive ability and operates on supplies down to -/+2.5 volts. Try it No guarantees though.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  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
AF filter using opamps - substitution of opamps neazoi Solid State 19 5th October 2011 04:01 PM
Need a better opamps msj965 Chip Amps 2 20th March 2010 05:34 AM
OPamps xaudiox Swap Meet 2 31st August 2006 02:40 AM
FS: Power Chip OpAmps and other OpAmps & D to A Converter dtm1962 Swap Meet 4 12th January 2006 10:07 PM
Opamps seiko_citizen Swap Meet 7 3rd May 2005 03:09 PM


New To Site? Need Help?

All times are GMT. The time now is 12:58 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