Boucherot Cell ( Zobel) not required for the TDA7294 ? - diyAudio
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Old 18th December 2007, 07:22 AM   #1
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Default Boucherot Cell ( Zobel) not required for the TDA7294 ?

The Application data says that the Zobel is not required for supply voltages higher than +/- 25 V .
Is everyone using the TDA7294 without the Zobel network without stability problems ?
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Old 17th September 2014, 02:40 AM   #2
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I have been looking also at these and see the post is from 2007.
Have you ever used this device? The challenge for me is cooling at the stated power level.
Normally for that power level I have tremendous surface area for the output devices against the heatsink compared with this device. Any experience with this?
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Old 17th September 2014, 04:37 AM   #3
sangram is offline sangram  India
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The TDA series chips are extremely fragile with very ambitious specifications. They sound good enough for the most part, but you should assume any chipamp is to be used well within its ratings. 50% is a good starting point, may need downward revision. Once you accept those limitations, they can impress you.

I used these as a stereo kit, almost 20 years ago and lost one to unexplained failure. The other was repurposed into an amp for our bands bassist. It died, as expected, within a month of use.

The LM3886 is a very durable chip by comparison, almost impossible to kill - believe me, I've tried... It clips horribly when pushed hard, but survives.
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Old 17th September 2014, 06:51 AM   #4
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From memory, my test of the TDA7294 vs LM3886 showed the TDA to sound more 'powerful'. Now that was easy to hear but not quite so sure how to describe it otherwise since they are essentially almost the same power rating.
I have a pair working for the past year with no problems and great sound. It is used everyday for several hours.
Supply is +/- 36 V unloaded. The heat sink is about 190x100x33 mm. The fins are vertical on the 100 mm side and about 25 mm deep. There are 20 fins. Works fine when played loud into min 6 ohms and most likely clipped only on the ocassional louder bass notes. I like this chip amp a lot.
If you try the mod's Ilimzn described long ago, it will possibly sound even better ! I've been planning to do that but haven't got there yet ! Too many things to do and not enough time !
The board is a Chinese board off Ebay. The bare board was US$4 !! But shipping added it brought it up to $9/- or something like that.
There is a Zobel on it . 10 Ohm 1/2 watt + 100nF cap. There is chip based relay protection for the speaker on the board. I had a all the parts and so bought only the board. The amp appears to require a burn in period. At least 50 hours I'd say. Not sure if my ears were getting used to it or it was getting better. But compared to some small classD amps and other AB discrete amps , overall, I prefer it over the others!

2007...Hmmm... ....the interest hasn't flagged yet for this chip ! Remember there is a current boosted circuit also to try ! A pair of bipolar power devices used to up it's low impedance load capability . Search it on this forum.

Check the posts here;
Need help on this TDA7293 schematic
TDA7294 + Power Transistors AMP (TDA7293 to come also)

Last edited by ashok; 17th September 2014 at 06:58 AM.
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Old 17th September 2014, 08:35 AM   #5
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It can be omitted and the HOPS protection as mentioned in the IRAUDAMP reference designs added. The HOPS mod to suit the TDA7293/4 is given here:

DC Protection and High Output Peak Shutdown (HOPS) for TDA7293

DC protection is also added.
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Old 26th June 2016, 12:50 AM   #6
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I have a Marshall 100 watt head amp and that has a chip amp in it.
I think that's a TDA7294 too.
Its on a tidy heat sink with a small fan to keep it cool.
Murton-Pike Systems PCBCAD51 pcb design software.
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Old 26th June 2016, 01:29 AM   #7
JMFahey is offline JMFahey  Argentina
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Both LM3886 and TDA729* have exact same case, which amounts to two TO220 packages side by side which dictates how much heat can they pass through, you canīt beat Physics Laws.
One of them is rated 50/60W and works reliably, the other one, with exact same capabilities is rated 100W and dies often, as simple as that.
I use TDA7294 in 70W Musical Instrument amps and have no problems with them, but I use them within reasonable parameters, not the datasheet inflated ones.
And *always* use Zobel/Boucherot/snubber networks, even if they tell me I donīt need them.
Design/make/service musical stuff in Buenos Aires, Argentina, since 1969.
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Old 26th June 2016, 05:20 PM   #8
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depends on the speakers too.
absolutely not impossible to achieve a speaker load that seems allmost perfect ohmic load.
then it is pretty safe to ommit it.

but in my opinion it may not worth the trouble and the components.
V*A*PowerFactor = WATT
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