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Old 17th September 2014, 10:22 PM   #1
wazzy is offline wazzy  Zimbabwe
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Default My tda7294 Amp

This is my attempt at building an amp using the tda7294 ic.
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Old 22nd September 2014, 03:57 AM   #2
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Nice built.

The capacitors could be closer to the TDA.

Gajanan Phadte
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Old 22nd September 2014, 03:42 PM   #3
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by gmphadte View Post
Nice built.

The capacitors could be closer to the TDA.

Gajanan Phadte
the smoothing capacitor + rectifier + transformer loop MUST be kept small for least interference.

The smoothed DC can be any length since cable impedance does NOT affect DC.

The on board local decoupling does the job of supplying current demand at HF and VHF.
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Old 22nd September 2014, 10:31 PM   #4
wazzy is offline wazzy  Zimbabwe
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Quote:
Originally Posted by AndrewT View Post
the smoothing capacitor + rectifier + transformer loop MUST be kept small for least interference.

The smoothed DC can be any length since cable impedance does NOT affect DC.

The on board local decoupling does the job of supplying current demand at HF and VHF.
Makes sense to me, I have 1500uf local decoupling on the boards and 24700uf per rail on the smoothing capacitors. The amp is absolutely silent when powered on no hum at all and the sound is pretty dynamic too.
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Old 8th October 2014, 10:24 PM   #5
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Pretty neat asymmetrical heatsinks!

Could you also post a pic of it when closed?

I still have about 50 caps of 12,000uF. Maybe I should put them all in one TDA7294 amp just to boast...
(originally bought for a TDA7294 dual supply-rail project, the testversion had 2x24,000@+/-20V and 2x54,000uF@+/-40V with 1000uF on the PCB for each voltage ).
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Old 14th October 2014, 09:59 PM   #6
wazzy is offline wazzy  Zimbabwe
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[IMG]Click the image to open in full size.[/IMG] Thanks for that it was from an old car amp. Did you hear any difference using the different voltages?
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Old 14th October 2014, 10:00 PM   #7
wazzy is offline wazzy  Zimbabwe
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Click the image to open in full size. this is the back...
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Old 15th October 2014, 09:09 PM   #8
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Originally Posted by wazzy View Post
Did you hear any difference using the different voltages?
It switched between the voltages by itself, it is a function discussed in the datasheet.
I never got it to work properly and one blew up, so I left the project for years until I found cheap boards in China for the regular use and shortly after, this thread. (And still have not finished one )

One thing that always puzzled me is that my version clipped the signal at 25V (oscilloscope, not a voltmeter showing rhe RMS or average voltage). Why it clipped at 25V with a 20 and a 40V supply, I never found out.

Last edited by ric-paul; 15th October 2014 at 09:11 PM.
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Old 15th October 2014, 10:08 PM   #9
wazzy is offline wazzy  Zimbabwe
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So were you using the high efficiency application? To be honest I have not tried this implementation so I defer to more experienced members.
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Old 16th October 2014, 07:14 AM   #10
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Main reason for doing it is being able to wring the most power out of it. I wanted to use it on a 4ohm speaker, and back then, it was the cheapest/simplest solution I could see (mid 90's) to make a subwoofer-plate amp of about 150Wrms@4ohm on a 12" sub with active filtering down to 24Hz within 3dB.

If I had seen this thread back then, I wouldn't have had design a PCB, to have custom transformers wound, to order everything in 5 fold with the plans to sell 4 of them, etc...

I should also have left it to the more experienced members...

It did work for a while though, just not putting out the numbers I had hoped, but enough for some decent rumble in the livingroom of my student dorm. (But the reference was my 15"sub on a car cross-over + caramp + battery + 12V 5A supply, so we were spoiled already).

Last edited by ric-paul; 16th October 2014 at 07:19 AM.
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