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Old 28th February 2011, 11:29 AM   #1
sesebe is offline sesebe  Romania
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Default 7293 parrallel or bridge/paralel for best sound?

Hello all,

I want to use Tda7293. I do not want a discrete or LM configurations.
The amplifier will have 3 TDA7293 in paralel for paralel only configuration, or 2 IC paralel conected in bridge with 2 IC paralel (4 IC per channel).

What is the best configuration for best sound? (under these conditions

Power supply 2*40V, load 8Ohm (150W RMS/250W Music for speakers).
The amplifier will be used 90% from time at 20-30W mean power but I want a very high reserve for peak power (over 150W) and a high slewrate.

I searched the forum but have not found a clear answer.

Thank you
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Old 28th February 2011, 05:24 PM   #2
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The sonic differences, if audible at all, will be small enough to be a question of taste. You won't find a clear answer except if you build both and compare them yourself.

From a heatsinking point of view it makes more sense to either use 2 single ended ICs in parallel or 3 BTL in parallel.

If the datasheet specifies that 40 V give 100 W into 8 Ohm (10 % THD!), it is not likely that you get 150 W just by using several ICs in parallel.

90% at 20-30 W mean power? Either your speakers are really bad or you are deaf or you soon will be.
If you've always done it like that, then it's probably wrong. (Henry Ford)
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Old 28th February 2011, 06:02 PM   #3
asbjbo is offline asbjbo  Norway
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Just to elaborate on pacificblue's comment: If we guess that your speakers have low efficiency, say 85 dB @ 1 W @ 1 m, we can guesstimate that 30 W is somewhere around 99 dB @ 1 m for one speaker. We can also conveniently guess that the loss in SPL due to the listening distance being greater than 1 m roughly cancels with the gain from using two speakers, leaving us with an average SPL around 99 dB in the listening chair using two channels of 30 W each.

However, uncompressed music has a dynamic range of perhaps 20 dB, so to reproduce real musical dynamics you will need quite a bit more power than the average level. 20 dB peaks takes 100x more peak power than the average. So, if your 20-30 W mean is correct, you should be looking at something that can deliver 2-3 kW peak for correctly scaled musical dynamics (and inventing speakers that can take all that power without melting). 20 dB peaks above 99 dB average will be really loud, as in a jet fighter taking off 200 ft away. Of course, if you only listen to highly compressed pop music, you might not need more than 9-12 dB headroom, or somewhere in the 150-500 W range. All assuming that your 20-30 W average is correct.

I'm curious: What speakers are you going to drive with these, for what type of music, and in what sort of room? How did you estimate 20-30 W mean power?

Last edited by asbjbo; 28th February 2011 at 06:04 PM.
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Old 28th February 2011, 06:35 PM   #4
sesebe is offline sesebe  Romania
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Ok! Maybe the power is to big but I know what I mean.
My speakers have a high sensibility and are good enough to deafen anyone in normal circumstances when use this power.
Maybe under 20-30W is the correct expresion, but if this power is used in 20-80Hz bandwidth you will see that is not to much.
At 40 V the peak power is around 144W
(power supply - voltage drop in IC (~6V)) squared /Rload.
In bridge configuration the peak power is around 578W
(positive power supply + negative power supply- voltage drop in IC (~12V)) squared /Rload. In the same time the slewrate will be double.
The peak power is specified only from cliping poit of view.
In bridge configuration the cliping will be at a very high output and is unlikely to be touched.
Question is whether it is worth the complication and the necessity of enlarging the heatsink.
When I will finish I will post the layout together with a complexe protection and maybe some photos, but I need your help until then.

And pacificblue I like you post.
I think that here there are people that allready made these tests.
I do not have enough time to test every configuration and is a good ideea to have a second opinion.
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Old 28th February 2011, 07:03 PM   #5
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99 db is already really loud. At workplaces it is usually obligatory to wear hearing protection when the SPL is 80 dB(A).
If you've always done it like that, then it's probably wrong. (Henry Ford)
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Old 28th February 2011, 09:56 PM   #6
sesebe is offline sesebe  Romania
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To limit the discution my speaker have 91dB @ 1 W @ 1 m, so more than you consider.
My previous posts provide enough information to generate an image about what I want.
I do not want power and sound pressure calculation. The forum is full with this and I don't know who needs this in real life at home.

Pacificblue what means 3 BTL in parallel? 6 IC's per channel? This was my first idea but I do not have enought space for so many IC's.
This amplifier need to be fit inside of an old amplifier box.

Asbjbo by the way you have been at least once near a military plane taking off when the afterburner lit? I was once and know very well what it means. And to not start another comment I do not have any problems with hearing.

I start this topic to have a second opinion regarding my question not to read a lot of breastbone comments. If this is the only comments that you can do beter not.
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Old 1st March 2011, 10:36 AM   #7
AndrewT is offline AndrewT  Scotland
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This is a very non technical reply to your bridging vs paralleling vs bridged/parallel.
If very good discrete based on lme498xx is given 10/10 for sound quality, then I would rate the three options as:
Single - 9/10
Parallel - 8.5/10 if you feed the same speaker impedance
Parallel - 8/10 if you feed a lower impedance speaker.
Bridged - 8/10 if you feed a doubled impedance speaker
Bridged - 7/10 if you feed the same impedance speaker.
BPA - 8/10 if the speaker impedance is high enough to not trigger any of the protections.

I believe all the multiple chip versions are poorer sound quality than the best single chipamp.
regards Andrew T.
Sent from my desktop computer using a keyboard
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Old 2nd March 2011, 08:22 PM   #8
sesebe is offline sesebe  Romania
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Thank's all of you who reply to my post.

I supose that that these are the only answere that I will receive in this forum.
It was a joke and I hope to receive more reply, maibe from people who made other tests.

Audio electronics is unfortunately not my strong point in electronics but I'll try to give answers, in my time limit on how many posts on that side of electronics were I'm really master.

Firt replay from me in this forum is on Improving heat transfer of IC.
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Old 12th January 2012, 10:22 PM   #9
sesebe is offline sesebe  Romania
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I'm back.

I finish the schematic for my TDA7293 design.
I is a MOS g class for a 2 parallel version.
I run some measurements and seems to be a promising design.

I will post in a short time some measurements and photos of testing board.
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Old 17th January 2012, 07:13 PM   #10
sesebe is offline sesebe  Romania
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Default Screenshot's


The schematic use two TDA7293 in parallel like in datasheet. I powered the IC's with 20V on low rail and 40V on high rail.The G class (power supply modulation) it is applied only to power pins (13 and 15) and it is made with MosFet's.

Some measurements and photo of test board and test setup:
Attached Images
File Type: png Class G start modulation.png (81.0 KB, 553 views)
File Type: png 20khz_8ohm_max_power.png (92.8 KB, 536 views)
File Type: png 20khz_square_4ohm_max_power.png (87.9 KB, 521 views)
File Type: png 50khz_4ohm.png (94.3 KB, 504 views)
File Type: png sweep_10hzto100khz_20khz_marker_.png (102.6 KB, 486 views)
File Type: jpg DSC00175.JPG (591.4 KB, 221 views)
File Type: jpg DSC00174.JPG (616.5 KB, 210 views)
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