Optimizing TDA7294 Output - Page 52 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 14th August 2013, 01:02 AM   #511
diyAudio Member
 
blakkshepeaudio's Avatar
 
Join Date: Sep 2010
Location: Country Victoria Australia
Quote:
Originally Posted by danielwritesbac View Post

>>> snipola
So I contacted Zoe Tsang (Not a financial affiliate) and requested this listing: Two board *stereo* kit TDA7293 Parallel amplifier
And I made this schematic.
And I made these assembly photos.
It is also in my signature line.

<<<< exit snipolito
Daniel,

Thanks for that clarification. I have bought a few fleabay amps over the years and board layouts have varied from good to appalling.
Nice to find a good one !

Kind regards,
Keith Arnold
blakkshepeaudio
  Reply With Quote
Old 30th August 2013, 03:42 PM   #512
diyAudio Member
 
andrewlebon's Avatar
 
Join Date: Feb 2008
Default TDA7294

TDA7294 with dc protection
Attached Files
File Type: pdf TDA7294 Doc.pdf (609.8 KB, 244 views)
__________________
[image][/image]"It's Better to try and fail than to never know and always wonder"
  Reply With Quote
Old 29th October 2013, 08:23 PM   #513
jayadev is offline jayadev  India
diyAudio Member
 
jayadev's Avatar
 
Join Date: May 2006
Location: Kerala
Quote:
Originally Posted by andrewlebon View Post
TDA7294 with dc protection
I wonder what they tried to achieve making this extra extensive layout.

ne5532 as dc servo ?
Ne5532 as voltage comparator for lm317..

What is that 470ohm, 0.5 ohm and 7.5k doing near the speaker ?
__________________
"One good thing about music, when it hits you, you feel no pain." - Bob Marley
  Reply With Quote
Old 18th December 2013, 10:51 PM   #514
diyAudio Member
 
Join Date: Aug 2013
Hi all,

Nice work Daniel and all who contributed to this great thread ...

I have one simple question about the schematic in post 461...
http://www.diyaudio.com/forums/attac...djustable2.gif

what is the purpose of the 220pF capacitor between the input pins? is it RF filtering? and what sonic effect does adding this capacitor have and the effect on the phase and magnitude of input signal like tyger23 mentioned in post 470?

Best regards.
  Reply With Quote
Old 20th December 2013, 11:37 PM   #515
diyAudio Member
 
Join Date: Aug 2013
Another question...What is the voltage rating for the bootstrap capacitor?
  Reply With Quote
Old 22nd December 2013, 12:51 PM   #516
diyAudio Member
 
Join Date: Aug 2013
Very useful guys thanks a lot
  Reply With Quote
Old 23rd December 2013, 03:21 AM   #517
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Quote:
Originally Posted by sghr220 View Post
I have one simple question about the schematic in post 461...http://www.diyaudio.com/forums/attac...djustable2.gif what is the purpose of the 220pF capacitor between the input pins? is it RF filtering?
It is to discourage RF. This is especially useful in the case of computers since would wouldn't want attempt amplifying the noise of a source that runs on extremely convoluted mess of a power circuit. Actually an inductor based filter would certainly work better, but it would not be so simple nor as inexpensive as the 220pF.
Quote:
Originally Posted by sghr220 View Post
and what sonic effect does adding this capacitor have and the effect on the phase and magnitude of input signal like tyger23 mentioned in post 470?
Testing input through output will show nothing other than you put in the cap, but this does not change any audible aspects of the amplifier. 330pF is also okay.

Although I loved the older production TDA7294, I absolutely hate the new production. So, unless you've got some new old stock sitting around, I'd recommend to avoid new TDA7294 new version craptastic waste of time. Instead of that, go with TDA7293's--those still sound a lot like they're supposed to.
Quote:
Originally Posted by sghr220 View Post
Another question...What is the voltage rating for the bootstrap capacitor?
50v, 63v, 83v, 100v are all suitable.
__________________
Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.
  Reply With Quote
Old 23rd December 2013, 02:12 PM   #518
diyAudio Member
 
Join Date: Aug 2013
Quote:
Originally Posted by danielwritesbac View Post
It is to discourage RF. This is especially useful in the case of computers since would wouldn't want attempt amplifying the noise of a source that runs on extremely convoluted mess of a power circuit. Actually an inductor based filter would certainly work better, but it would not be so simple nor as inexpensive as the 220pF.
Spot-on Daniel thanks a lot for the detailed explanation.

Quote:
Originally Posted by danielwritesbac View Post
Although I loved the older production TDA7294, I absolutely hate the new production. So, unless you've got some new old stock sitting around, I'd recommend to avoid new TDA7294 new version craptastic waste of time. Instead of that, go with TDA7293's--those still sound a lot like they're supposed to.
Again you read my mind i have some NOS chips (to avoid the fakes) and a huge anodized heat all i need now is a good layout and i will give it a go. By the way i am going with your version named "TDA7294-Adjustable2" with some minor mods, I'll tell how it sounds as soon as i am finished.

Thanks and best regards.
  Reply With Quote
Old 4th January 2014, 01:30 PM   #519
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Guesstimation table for new production chips:
V7 TDA7293 = Real higher cost TDA7293
V6 TDA7293 = Real low cost TDA7294H (max 25+25vac transformer)
TDA7294 = TDA7295 or dirt cheap cull (terrible audio quality)
TDA7295 = TDA7295 or dirt cheap cull (terrible audio quality)
TDA7296 = Real TDA7296 OR a cheap substitute

This also affects authorized vendors. The ST chips that I have purchased from Mouser and Digikey have been identical to those in the eBay kits.

You really can buy an old-production quality TDA7294; but, it won't have "TDA7294" printed on the casing, AND all 15 pins will work.

Attempting to purchase TDA7296's sometimes works, and I guess that is because old stock of the less popular chip hasn't run out yet.
__________________
Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.
  Reply With Quote
Old 4th January 2014, 04:05 PM   #520
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
My above post has an error. It is actually TDA7294S that has all 15 pins working. That chip is great. It can be labeled as TDA7293 in cheap kits. Sounds good, but has TDA7294's voltage and load maximums. If the whole kit costs less than TDA7293's, then I think that 25+25vac transformer is maximum. Otherwise, those things work great. They're a lot better than new production TDA7294's.
Quote:
Originally Posted by sghr220 View Post
By the way i am going with your version named "TDA7294-Adjustable2" with some minor mods, I'll tell how it sounds as soon as i am finished.
Sort of a made for a "big" sound arrangement. The adjustable gain is needed to find an ideal gain setting which varies by power voltage. The sweet spot isn't really findable with fixed resistor values.
One missing trick!
It needed a variable input load since 22k images better but with Louder Mids and 27k has softer pleasant mids. That probably needed to be a variable resistor for the slight fine tuning that could be done with it.

From years and years ago, here's an alternative: My old chip has 100k feedback, 2k7+220u feedback shunt, 36+36vdc rails (if you have less voltage likewise decrease the gain too), and is otherwise similar to the newer schematics. I like the lighter current at small signal area for its prettier midrange and treble and decent imaging; however, it is not as bassy. Both adjustable input load and the BlareBuster circuit can work with it, for relatively easy fine tuning of the input impedance that is and isn't.

P.S.
If you decided to separate the rails, protect the small signal voltage amplifier's power pins with MBR1645 schottky so that they can't go more than 1/3rd of a volt lower voltage than the output buffer's power pins. This approach is listed on some "hi fi version" schematics online but the chip breaks if lossy diodes are used for the safety bypass. SO, I suggest upgrading the BY fast silicon to MBR schottky on those separate rails schematics. I didn't publish any like that, because actually doing it right is more complicated than building a better discrete amp, and half measures don't outperform the simplified bus rail system shown on my schematics.

P.P.S.
These chips explode immediately if the bootstrap cap is backwards or a bad cap. Might want to give that thing a quick checkup before powering on. Or the easy way--a 33u Nichicon ES, which is good quality and never backwards.
__________________
Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.

Last edited by danielwritesbac; 4th January 2014 at 04:10 PM.
  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
OPtimizing the VBE MUltiplier fglabach Solid State 41 17th January 2013 01:27 PM
Optimizing active crossover atledreier Multi-Way 27 19th August 2011 02:53 PM
optimizing the VBE multiplier hienrich Solid State 80 29th November 2010 10:25 PM
Interesting linestage optimizing ideas PixelPlay Tubes / Valves 5 23rd June 2008 10:18 PM
optimizing for efficiency Dwiel Solid State 13 10th May 2005 09:31 PM


New To Site? Need Help?

All times are GMT. The time now is 02:33 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