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Old 27th September 2011, 04:05 AM   #1
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Default TDA7293 single, bridge, parallel

I am going to evaluate TDA7293 in single, bridge and parallel operation modes. In this first post, performance of single mode will be presented.

I used a board (two channels configurable for stereo or mono-bridge) purchased from TaoBao. It is powered by a +/- 40 V supply.

THD vs power for 8 and 4 Ohms are shown here.

Distortion residual for 4 and 8 Ohms are near rated power are also shown below. Crossover spikes can be seen from the figures.
Attached Images
File Type: jpg THD vs power 4 Ohms.jpg (81.7 KB, 1425 views)
File Type: jpg THD vs power 8 Ohms.jpg (81.9 KB, 1338 views)
File Type: jpg IMGP3498.JPG (117.0 KB, 1360 views)
File Type: jpg 8 Ohm 61 W 1 kHz residual.jpg (82.2 KB, 1335 views)
File Type: jpg 4 Ohm 91 W 1 kHz residual.jpg (83.9 KB, 1226 views)
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Old 27th September 2011, 04:46 AM   #2
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Very cool !!!
I will Be looking foward to seeing some more of your results.


jer
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Old 27th September 2011, 04:58 AM   #3
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Gain of the board is set to 31 (30 dB).

The board is slightly modified for parallel operation. THD vs power for 8 and 4 Ohms load are shown below. Compared to single chip operation, higher output power is obtained. Lower distortion is obtained. On the other hand, distortion at rated output power is similar to that of single chip operation.

Less crossover spike is seen from the distortion residual.
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Old 27th September 2011, 08:50 AM   #4
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I cleaned up the wiring for parallel operation and run measurement again. THD vs power for 4/8 Ohms of two in parallel is shown in the figure below.

Comparison for single and two in parallel are shown for 4 and 8 Ohm loads, respectively. In all cases shown, parallel operation has lower distortion as expected. It also offers higher output power for 4 Ohms, from 70 W to over 100 W.

PS: Oscillation occurred for high output level in to 4 Ohms load. It was due to the wires connecting bootstrap pins (P12, P6) too close to wire connecting buffer driver pins (P11).
Attached Images
File Type: jpg THD vs power 4 8 Ohms x2 x1.JPG (191.3 KB, 185 views)
File Type: jpg THD vs power 4 Ohms x2 x1.jpg (145.3 KB, 133 views)
File Type: jpg THD vs power 8 Ohms x2 x1.jpg (145.2 KB, 115 views)

Last edited by panson_hk; 27th September 2011 at 09:02 AM.
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Old 27th September 2011, 04:09 PM   #5
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Panson,

Thanks for posting all of these results. Very interesting. I wonder if the decrease in distortion will continue as more chip amps are paralleled?

Also, 40VDC rails are getting a little high perhaps... what's the power dissipation like? Can you try 35VDC rails?

The higher levels of distortion that you observe at 20k is typical for this chip amp. It's not a great full range amp because the distortion above 1k rises too rapidly. It should be very nice in a multi-amped system for lower frequency use, however.

-Charlie

Last edited by CharlieLaub; 27th September 2011 at 04:11 PM.
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Old 27th September 2011, 11:26 PM   #6
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Hi Charlie,

I think +/- 40 V rails is fine for paralleling the chips. For single, it would be too high. Yes, a big heatsink is needed.

I think improvement for 4 Ohms will be more or less stop when paralleling up to four chips as LM3886.

I am also thinking to use a configuration "opamp + TDA7293 (slave)". We may have an amp with better performance where output stage in a single package with protection.

Panson

Last edited by panson_hk; 27th September 2011 at 11:36 PM.
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Old 29th September 2011, 10:30 PM   #7
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Quote:
Originally Posted by panson_hk View Post
Hi Charlie,
I am also thinking to use a configuration "opamp + TDA7293 (slave)". We may have an amp with better performance where output stage in a single package with protection.
Panson
Hi Panson,

If I understand what you wrote, you want to use an op amp driver instead of one of the TDA7293s as the "master"? Why do you think that would give better performance? Are you sure an all slave configuration will work, e.g. without one of them being the master? What would that gain over other "driver IC + output devices" designs?

-Charlie
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Old 30th September 2011, 03:15 AM   #8
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Hi Charlie,

We can find an opamp outperforming the front-end of TDA7293. The amp "opamp+TDA7293 output (slave)" may be a better amp.

I will try to see if TDA7293 can be operated in solely slave mode driven by another signal source.

Panson
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Old 30th September 2011, 03:17 AM   #9
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Interesting ideas there Panson - can the TDA7293 work as a kind of super output buffer? But isn't the voltage gain in this mode limited to +1 so the opamp's power supply will be the limiting factor?
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Old 30th September 2011, 03:33 AM   #10
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Quote:
Originally Posted by abraxalito View Post
opamp's power supply will be the limiting factor?
Good point!

May be Opamp + 7293 (slave) a low-power amp? A headphone amp? Or LME498xx + 7293 (slave) .....
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