Need Help with TDA7294 Stereo Amplifier

[ahsrabrifat]

Hi everyone,
I'm working on a stereo audio amplifier using two TDA7294 ICs and I'm a bit confused about the best configuration for my setup. I’ve seen various implementations using both bridge mode and parallel mode, but I’m not sure which one would be better for driving 8-ohm speakers with around 100W per channel.

Here are a few details about my build:

• Power supply: ±35V dual rail
• Speakers: 8-ohm, full-range
• Application: Home audio
• Cooling: Large heatsink with fan

My questions are:

1. Is it better to use each TDA7294 in single-ended stereo, or to bridge them for more power?
2. Are there any risks to reliability or sound quality when using bridge mode at 8 ohms?
3. Would parallel mode offer better thermal sharing and lower distortion for long listening sessions?

I’d appreciate any tips, schematics, or practical experience you've had with this chip in stereo or high-power configurations.

 

[danadak]

 

[Nigel Goodwin]

Hi everyone,
I'm working on a stereo audio amplifier using two TDA7294 ICs and I'm a bit confused about the best configuration for my setup. I’ve seen various implementations using both bridge mode and parallel mode, but I’m not sure which one would be better for driving 8-ohm speakers with around 100W per channel.

Here are a few details about my build:

• Power supply: ±35V dual rail
• Speakers: 8-ohm, full-range
• Application: Home audio
• Cooling: Large heatsink with fan

My questions are:

1. Is it better to use each TDA7294 in single-ended stereo, or to bridge them for more power?
2. Are there any risks to reliability or sound quality when using bridge mode at 8 ohms?
3. Would parallel mode offer better thermal sharing and lower distortion for long listening sessions?

I’d appreciate any tips, schematics, or practical experience you've had with this chip in stereo or high-power configurations.

It really depends what you're trying to do?, their output isn't 100W anyway, it's only 60/70W RMS at a fairly high distortion of 0.5%. However, by bridging two of them, thus using four, you could get 120/140W in to 8 ohms - bridging doesn't increase power, it allows the same power to a different impedance (each chip is providing 60/70W to 4 ohms). However, bridging increases distortion even more, and probably isn't a good idea. You would also need a different supply, as 8 ohm is +/-35V maximum, and 4 ohm is +/-27V maximum, and required for bridging to an 8 ohm load.

For home audio use a single TDA7294 per channel and 60/70W is plenty more power than you're going to need anyway, and as they shouldn't be running hard anyway, distortion will be considerably lower than when hitting the absolute maximum power.

Bear in mind volume is logarithmic, so 100W is only twice as loud as 10W - unless you live in a vast mansion, and have highly inefficient speakers, two single ended TDA7294's should be plenty.

I've seen various guitar amps using these chips, they seem to work pretty well, and are quite reliable - and they don't tend to use expensive huge heatsinks, despite their much higher power levels and considerable abuse.

 

[ahsrabrifat]

View attachment 150307

Thank you. Here I have found a design too. https://www.pcbway.com/project/shareproject/TDA7294_stereo_amplifier_7f5f30c5.html
It consists of
1. 6×22KΩ resistor 1/4W.

2. 2×10KΩ resistor 1/4W.

4. 2×680Ω resistor 1/4W.

5. 4×22uF capacitor 50V.

6. 4×10uF capacitor 50V.

7. 4×4700uF capacitor 50V.

8. 2×Capacitor 0.1uF(104).

9. 2×Capacitor 0.47uF(474).

10. 1×3 pin XHB connector base 2.54 mm.

11. 2×2 Pin screw terminal.

12. 1×3 Pin screw terminal.

13. 1×Bridge rectifier GBU808.

14. 2×IC TDA7294.

If I implement this, will I need a heat sink?

 

[ahsrabrifat]

It really depends what you're trying to do?, their output isn't 100W anyway, it's only 60/70W RMS at a fairly high distortion of 0.5%. However, by bridging two of them, thus using four, you could get 120/140W in to 8 ohms - bridging doesn't increase power, it allows the same power to a different impedance (each chip is providing 60/70W to 4 ohms). However, bridging increases distortion even more, and probably isn't a good idea. You would also need a different supply, as 8 ohm is +/-35V maximum, and 4 ohm is +/-27V maximum, and required for bridging to an 8 ohm load.

For home audio use a single TDA7294 per channel and 60/70W is plenty more power than you're going to need anyway, and as they shouldn't be running hard anyway, distortion will be considerably lower than when hitting the absolute maximum power.

Bear in mind volume is logarithmic, so 100W is only twice as loud as 10W - unless you live in a vast mansion, and have highly inefficient speakers, two single ended TDA7294's should be plenty.

I've seen various guitar amps using these chips, they seem to work pretty well, and are quite reliable - and they don't tend to use expensive huge heatsinks, despite their much higher power levels and considerable abuse.

Does TDA7294 need any heat sink?

 

[Nigel Goodwin]

Does TDA7294 need any heat sink?

Presumably it depends how hard you drive it?, but I assume with no heatsink at all you wouldn't be able to run it at any worthwhile volume - but bolting it to a decent metal chassis might be all that's required?.

Here's a link to a video about the Leak Stereo 70, a highly regarded amplifier from long ago:

It's rated at 35W per channel RMS to 8 ohms, both channels driven, but will considerably exceed that to 8ohms, and will also drive 4 ohms fairly well. I had one for years, an excellent amp, and as well as my home HiFi I used it as a PA amp, and for discos. I've seen many used for PA and even as guitar amplifiers, a really great old amp, and surprisingly bombproof.

The reason for mentioning this, and posting the YouTube link, is the picture before you even press play - it has a nice clear view of the top, clearly showing the tiny heatsink with four 2N3055's mounted on it!.

 

[danadak]

A quick test, if you choose not to do design analysis, take a tone generator, at some
moderate volume and freq, and using your IR handheld thermometer apply the generator,
first getting ambient reading off TDA package, and then apply generator and get reading
after some period, say 10+ secs or so. Then backtrack case T into Tjunction and compare
to datasheet max. You want a lot of margin. T is the enemy of reliability in semiconductors.

https://www.ti.com/lit/an/slua844b/slua844b.pdf

If its running too hot get out the metal, and use thermal paste to make low Theta-J
case to heatsink resistance.