Is it a joke to say pair of TDA7293 in parallel can deliver 100+W power into 4ohm - diyAudio
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Old 4th July 2011, 03:03 PM   #1
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Default Is it a joke to say pair of TDA7293 in parallel can deliver 100+W power into 4ohm

I fell it is a joke to say pair of TDA7293 in parallel can deliver 100+W power into a 4ohm load. This is concluded from my own experience of using 7293 in parallel.
My setup is as follows
1) two 7293 in parallel, by using standard modular application schematic as from the datasheet
2) power supply, two Agilent 30v 7.5A power supply
3) Agilent33250 signal generator
4) four 1 ohm dale resistors in serie (4.2ohm measured resistance) for load
5) Agilent MSO7054scope
Signal freq. is 1000Hz. The scope show that the output started peak-cut at about 18.6v. The max output power is merely 82w. I think this is what I can get from a IC PA? Even in that datasheet, it does not say the parallel application can output more power, it only says the parallel application can more easily drive lower impedence load. I might have got fake ICs? I really think my ICs are real.

Here are some pictures of the staff I have used.

By the way, the signal distortion is already very obvious at 20KHz. If anybody interested, I will post more pictures later.

This is the load
SNC00281.jpg

This is the DM
SNC00282.jpg

This is the signal generated and view from scope when directly feed the signal into scope channel, which show what measurement tools were used and they work perfectly.
SNC00276.jpg
SNC00277.jpg
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Old 4th July 2011, 04:12 PM   #2
tinitus is offline tinitus  Europe
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only very good SS amps doubles power into half impedance load
or else they are designed to do so, by using lower supply voltage
so if you set it up to do 30watt into 8ohm, it might double its power to 60watt into 4ohm

no amp design pushed to its limits into 8ohm will double the power into 4ohm
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Old 4th July 2011, 04:14 PM   #3
AndrewT is offline AndrewT  Scotland
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It is no joke.
It is very easy to design and build an amplifier that can deliver 100W into a 4r0 resistor. That is what you see in the chipamp manufacturers' datasheets.

What they don't tell you is whether these same amplifiers can deliver real power into real 4ohm speakers that have a very significant reactance.

4r0 and 100W requires 28.28Vpk and 7.07Apk.
4ohm and 100W could require 28.28Vpk and >21Apk. There is the problem that they don't admit to !
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regards Andrew T.
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Old 4th July 2011, 04:25 PM   #4
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well I bought a board on ebay a while back for fun, it featured 2 7293's in a stereo setup with power supply caps and a bridge for less that $20 US. I hooked it up to a 30-0-30 transformer and it gave me around +/- 44VDC with no load. I measured about 72 watts RMS just before clipping into an 8 ohm load (actually 7.5). So a parallel pair should deliver 100 watts plus into 4 ohms given a proper power supply(voltage and current). You need to deliver 28volts Peak or 20 volts RMS to get the 100 watts at 4 ohms. Seeing how your power supply was only +/- 30 there is very little room for losses. The data sheet shows a power output of 75 to 100 watts at 4 ohms with +/- 29 vdc(distortion 1-10%) under ideal conditions (Page 3). So your setup is within spec.

I tried to upload the data sheet but it is too big
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Old 5th July 2011, 04:46 AM   #5
lithoc is offline lithoc  Malaysia
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to get >100W @ 4 ohm, I believe you need higher voltage. According to datasheet, you need >40v.

I've a pair of TDA7293 in parallel. unfortunately the chip blew off before I can here any sound from this chip.

Last edited by lithoc; 5th July 2011 at 04:48 AM.
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Old 5th July 2011, 05:27 AM   #6
a.wayne is offline a.wayne  United States
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Avoiding TDA7293 pitfalls


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Old 5th July 2011, 11:11 AM   #7
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multisync: I agree with you that my setup is within spec. But why so many still say that higher voltage may yield higher Pmax out? When we rise up the power supply voltage, we also bring up the risk. That is why we see so many 7293 blow into smoke. I have no doubt that single 7293 can output 70W+ at resonable distortion. But the parallel application, even when you follow the datasheet, cannot deliver the desired output power. Have you ever tried or wanted to try the 7293 parallel?
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Old 5th July 2011, 11:18 AM   #8
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AndrewT: The problem is that even you follow the setup in the datasheet, you cannot get the desired result. And I have not find post in this forum which gives concrete fact that the modular application in the datasheet delivers higher power than a single 7293 delivers.
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Old 5th July 2011, 11:20 AM   #9
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Quote:
Originally Posted by a.wayne View Post
Do you mean 7293 itself is a pitfall or there are pitfalls when you use 7293?
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Old 5th July 2011, 11:38 AM   #10
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Just post more information about the setup

The setup(PAmp+Scope+DM)
CIMG2832.JPG

The scope show peak cut at 20.467vRMS
CIMG2843.JPG

20KHz squre wave output at 11.776vRMS
CIMG2833.JPG
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