TDA-7294 - cheap audio power opamp - any modern alternative ( class A) ? - Page 1
Forum section: electronics / general

author: Hella_Wini22
author_rank: Contributor
timestamp: November 19, 2024, 06:55:00 am
content: I like the chip, but it's old and is getting pretty expensive on hard to get on that account, even though it used to be golden choice many years ago.To me, it was interesting not just as audio power amp, as it was fast enough to be used for many other uses.For example, one could use it to make a simple, but very decent variable benchtom DC power source. Or simple signal generator etc.So I wonder if there is modern alternative.Preferrably something with MOSFETs instead of bipolars, so it would be faster and more robust.That TDA could IIRC work up to 10 A peaks and 50V power supply, dissipating maybe 60W or so on a solid heatsink.Any ideas ? 🙄Or maybe I should just roll up my own from some nice opamp a pair of FETs to fit my needs ?It's certainly doable, but I was hoping for a solution of one cheap, ubiqutious component which could a good base for many simple projects...

author: Chicane
author_rank: Contributor
timestamp: November 19, 2024, 07:29:20 am
content: No modern chips are class A. Not sure if there are even AB left still. It's all class D for years. I don't even know if anyone makes a discrete class A still. They will be an arm and a leg, if you can even find one.Class A is not very practical in a car too. Having only 12V, it will be hard to get high in power output.Also not sure why do you insist on class A with all the tire, engine and road noise. It's going to be hard to tell the difference from AB.

author: Hella_Wini22
author_rank: Contributor
timestamp: November 19, 2024, 07:45:41 am
content: Quote from: Chicane on November 19, 2024, 07:29:20 amI don't care about the car or audio. As written in OP, it was interesting component for alternative uses. LIke, for example, making a ultracheap relatively nice analog power supply with regulation.Or signal generator with power output for low-ish frequencies (say up to 1MHz or so).

author: Chicane
author_rank: Contributor
timestamp: November 19, 2024, 08:20:20 am
content: You can use something like LM317 or LM117 with an external power PNP for that. It will be cheaper than TDA-7294.Mosfets are used for switching, not regulation in the sense of analog. SMPS, a DC-DC converter is what they are good for, but that is far more complex to build and comes with a lot of noise in the output.

author: Hella_Wini22
author_rank: Contributor
timestamp: November 19, 2024, 08:27:12 am
content: Both of those are not even a bad joke, compared to TDA-7294.It can do 10-ish A and 50V without anything external. It also has a push-pull etc.

author: Postal2
author_rank: Frequent Contributor
timestamp: November 19, 2024, 08:38:55 am
content: Quote from: Hella_Wini22 on November 19, 2024, 06:55:00 amTDA7294 costs $1 on Aliexpress. The sound is a bit provincial, compared to class D it looks weak. But if you have experience with this particular chip, it is sold by weight, I don't see any shortage.

author: Hella_Wini22
author_rank: Contributor
timestamp: November 19, 2024, 09:03:45 am
content: Quote from: Postal2 on November 19, 2024, 08:38:55 amIt's trivial to push TDA-7294 to work in class A. One simple ultracheap opamp and feedback can easily erase its dips.It's also dead simple to run it in bridge mode, quadrupling the power etc.But since we all grew up and chips are old, I'm looking for better, more modern, faster alternative.

author: tom66
author_rank: Super Contributor
timestamp: November 19, 2024, 11:24:15 am
content: High power op-amps exist:https://www.ti.com/product/OPA541The problem is the market has been replaced by class D. It wouldn't have been unusual to find an amp IC like this in a car stereo but nowadays everything will be SMD and class D. It's more power and cost efficient.You could always use a generic high current op-amp to drive a class-AB stage and effectively get the same performance as this IC. If you use TO-247 transistors and SMD op-amp capable of driving +/-500mA for the bases (e.g. OPA547), you can probably get away with quite a small solution.

author: dietert1
author_rank: Super Contributor
timestamp: November 21, 2024, 04:14:03 pm
content: Quote from: Postal2 on November 19, 2024, 08:38:55 amNo, chips like TDA7294 or LM3886 don't have a sound. Those are linear amplifiers of good quality and large noise free dynamic range. The good quality and usability of those solutions are the background of "no modern chips". Higher power requirements, e.g. for subwoofer or PA, are well covered by class-D integrated circuits.Only audiophools run after special solutions like discrete and/or class A. Once they found something with audible distortion, they will praise its sound.Regards, Dieter

author: David Hess
author_rank: Super Contributor
timestamp: November 21, 2024, 07:42:12 pm
content: I do not see any lack of cheap integrated class-AB amplifiers, including the TDA-7294:https://www.mouser.com/c/semiconductors/audio-ics/audio-amplifiers/?class=Class-AB&mounting%20style=Through%20Hole&instock=y&sort=output%20power%7C1The LM3886 is the obvious alternative.QuoteI do not think that matters for an integrated solution where the bipolar transistors are fast and protection circuitry is included. Speed for an integrated solution is limited by other things, like it is for integrated operational amplifiers.

author: coppercone2
author_rank: Super Contributor
timestamp: November 23, 2024, 02:03:17 am
content: I miss these types of chips too, people underestimate how well they work in various custom circuits for whateverAll the newer ones seem to oscillate alot easier.also its almost expected to get aD-ealer to show up in these high power op amp threads for no reason. It might make sense at a cost sensitive auto parts manufacturer, but this is a electronics forum. Things run on selenium, tubes, spark gaps and class A just fine for us. It can alsopower some interesting transducers and stuff meant for science.If the thread read "I am a new hire for a major automotive company operating in a cut throat market...." then maybe the response would be welcome. Lol, I almost feel like someone is trying to goad people into developing D-topologies

author: themadhippy
author_rank: Super Contributor
timestamp: November 23, 2024, 02:18:34 am
content: QuoteIs a fiver expensive for a 100w amp? your gonna pay a lot more than that for a suitable transformer to power the thing.

author: coppercone2
author_rank: Super Contributor
timestamp: November 23, 2024, 02:20:41 am
content: not exactly a good product if you wanna make a small business that will run out of chips eventually, if you can see it going for yearsI was looking for modern parts too. I have some circuits that oscillate with the new 'efficiency' improvement they added to these chips. Its making me go way more discrete. Apex audio power amp is "Class C"!!!Alot of people are complaining about new op-amps being harder to use for anything but bog standard circuits because of low power stuff their doing in them. Difficult to compensate composite amps. Composite amps are the the kind of thing the companies should encourage. !