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-   -   Using a pair of TDA7293 im parallel... (http://www.diyaudio.com/forums/chip-amps/43009-using-pair-tda7293-im-parallel.html)

Luke123 20th October 2004 06:43 PM

Using a pair of TDA7293 im parallel...
 
...Is it to approximate a better voltage source?
So you get real doubling of power in 4 ohms?
Or a better control in LF where reactive loading can be important?

Luke123

Cro maniac 21st October 2004 08:12 PM

Hi Luke123 !

Because 7293's don't need current sharing resistors when connected in parallel you'll get half output impedance and double damping factor. So, yes, it will be better voltage source and will have better control in bass.
You'll get doubling of power if you raise power supply voltage because each chip will "see" twice of speaker impedance when connected in parallel. So, with 4 ohm speakers, each chip will see 8 ohms so you'll have to raise power supply voltage from +/-29V to +/- 40V to get double power.
If you leave power supply of about +/- 29V you'll have to use 2ohm speakers to double the power output.

carlosfm 21st October 2004 09:06 PM

2 Attachment(s)
Quote:

Originally posted by Cro maniac
You'll get doubling of power if you raise power supply voltage because each chip will "see" twice of speaker impedance when connected in parallel. So, with 4 ohm speakers, each chip will see 8 ohms so you'll have to raise power supply voltage from +/-29V to +/- 40V to get double power.
If you leave power supply of about +/- 29V you'll have to use 2ohm speakers to double the power output.

What? :eek:
:whazzat:

Look at this example, taken from the LM4780 datasheet.
Observe the power at +/- 30V, single chip at 8 ohms, and two paralleled chips at 4 ohms.
The voltage is the same.
The power rating is double.

Cro maniac 22nd October 2004 02:32 PM

Quote:

Observe the power at +/- 30V, single chip at 8 ohms, and two paralleled chips at 4 ohms.
Carlosfm, maybe I missed something here, but I don't see the difference in what you and I said. In your example with LM4780 you noted that you will get double power with same supply voltage with parallel connection if you cut speaker impedance to one half. It is exactly what i said.
Luke123 asked if he would get real doubling in power when using 4ohm speakers and 2 chips in parallel. If power supply voltage stays the same as for single chip when using 4ohm speaker (2x29V) the only advantage will be that chips will now share the power dissipation, but power output will not be doubled. 2 LM3886 in parallel also use 2x35V for powering 4ohm speakers, not 2x28 as for the single chip.

Luke123, try to google for a100-daten-301.pdf. On page 14 you have tables with available power with various connections of TDA7293. With 2x40V and 2 chips in parallel clipping point will be about 120W on 4 ohm speaker.


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