TDA7396 trouble

[jeeptechfred]

Today I measured the new chip amp from pin 5 to the ground pin and pin 7 to the ground pin. In both situations I got a measurement of several kohms. I removed the old chip amp. I then rechecked the inputs and outputs on the board. All checked okay so I installed the chip and it worked correctly. Thanks for your help!!

Problem solved

[soundguruman]

You can run 8-16 ohm load. A 4 ohm load causes it to fail quickly.
This is why a lot of them fail.

[g1]

They're rated for 2 ohms minimum. So if there are designs where they're failing at 4 ohms they must have a very inadequate heatsink.
Or maybe you're talking about a different part number.

[Enzo]

Or maybe just talking, period.

[Leo_Gnardo]

They're rated for 2 ohms minimum. So if there are designs where they're failing at 4 ohms they must have a very inadequate heatsink.

"Blue sky" ratings from the manufacturer. Also remember real speakers have impedance curves, and for some frequencies, the impedance is lower than the supposed nominal impedance averaged over all "frequencies of interest." You hit the right note, poof goes your chip. I've found it best practice to not challenge chip amps, or sand amps of any sort for that matter.

[g1]

C'mon, skip the subtle diplomacy and give us some more of the good stuff .

edit: should have included this

Or maybe just talking, period.

[Leo_Gnardo]

C'mon, skip the subtle diplomacy and give us some more of the good stuff .

OK, and I'll try to do it in my best broken French, the language of diplomacy, sort of.

IMHO, les amplificateurs de chip sont merde.

Something like that. Or disposable, which is the same en Anglais or in French, give or take a carat or accent acute or grave.

Hope that does it for ya!

[g1]

Oops! Sorry Leo, that comment was meant for Enzo. This slow motion forum action is really getting wearisome.

[Leo_Gnardo]

Oops! Sorry Leo, that comment was meant for Enzo.

Wayll then, par donny mwa, svp.

Your international ambassador of good will, LG.

[km6xz]

Talk...and 2 ohms

Leo, this is a part that is optimized for 14 volt operation, directed to automobile electronics and has a different topography than a conventional AB common emitter push-pull circuit. It is rated as most efficient at low Z loads and have several key protection and current limiting features making it very well suited to powering speakers in car use that often drop below 2 ohms, such as unlimited short circuit rating. This defect in this case is a good example of the protection circuit working, no DC offset yet having a shorted MOSFET transistor. Try that with a conventional AB amp module. Normally you would expect smoke, burned pc board, fuse blowing and burned voice coil.If one has not kept up with newer chips and modules for home entertainment equipment they will be surprised how much has changed, to drive higher efficiency, lower supply voltages, single supplies, low part counts, lower distortion, higher power, and more protection. Spend an afternoon with the spec sheets for all the TI parts for example that use Class D and get in the 90's% range on low single voltage with very low part count. Portable electronics popularity has upped the R&D budgets and some really cool devices are available for very low cost.A 300 watt Class D used to be complicated to build but now is easier and cheaper than a 25 watt discrete bipolar linear, besides not needing much heat sink or power supply. I just built a utility bench powered speaker, just a wooden box with several input jacks for speaker direct, speaker attenuated( a 100:1 and 10:1 switchable power divider) or -10 or +4 line input. Used a single chip for the amp, and a single chip supply. It is 30 watts, sounds good and cost $30 to build, most of that being the speaker. It runs on a 12volt single supply that generates 18 volts from a single chip boost regulator and is so efficient, can be used with a small lead acid battery for total isolation for days. I got the chips free from TI but the $30 was the price if I bought the parts locally. If the battery terminal voltage sags from low charge, it still works, just pulls more current since it is a boost regulator. It runs fine on 5 volts in but it is not as efficient, only about 85% but when running on 12 volts the amplifier and supply combine to get right at 90% total system efficiency: power from source>power at load. No heat sinks are used and nothing gets warm except the VC of the speaker.

[Leo_Gnardo]

Talk ... and 2 ohms

I'm glad to hear of your success with your chip amp Stan & of course you properly engineered your powered speaker. Thanks also for the explanation that this TDA was intended for 14V rail, in automobiles.

I've encountered way too many cheapo guitar amps that use this or another TDA, run with bipolar 40V rails and a chip of aluminum for a heat sink. Add to that circuit board traces that practically evaporate when attempting to remove the roasted chip. Most of these I'd classify as disposable.

There is one Crate model however that no owner wants to part with. A 2 x 8 speaker, separate amp for each, and built-in chorus that sounds very attractive. The whole amp is the size of a lunchbox - very portable. Chip outputs but - thank goodness it's rarely the case that one of these goes bad. Only if the user tries to run the speaker output into a DI that's grounded, because the speaker outputs are "floating" and the circuit can't survive having one of its speaker leads attached to ground.

[km6xz]

What is being grounded? That sounds more like an improperly used or designed DI. At least flip the ground lift switch would solve the problem.
Showing him how to use or even select DI that will work only takes a second.
There are more chip outputs in operation today than discrete bipolar by far and they tend to be reliable and with effective protection circuits.
I tend to look at the task to be done more than what is familiar habit. In some cases discrete will work best, in many tasks class D or single chip solutions are going to be more reliable and rugged with better performance. There are lots of ways of generating soundwaves, all are better in something, none better in everything. In a few cases, tubes are good choices but many nowadays.
That is the nice thing about self contained, powered speakers, how it gets its work done is up to the designer to optimize the system as a whole rather than be constrained to the I/O standards for interfacing with external gear which became standard long ago when they were effective choices for the technology available at the time. With a powered speaker, only the input signal interface is required to be traditional. If designed today, the traditional consumer -10dbv differential input would not be considered as a standard. Neither would a 1/4 phone plug/jack. The only big change in interconnection of gear was years ago when bridging transformers were discarded for voltage levels of terminated loads instead of power levels (dbm) of terminated loads for maximum power transfer. Otherwise it has been stagnant until digital I/O became the interface signal type of choice for most modern applications. Even there you are constrained to a few standards that are almost obsolete. AES/EBU with XLRs just looks like a kluge, taking up way too much panel space and not good for stray capacitance for example.
The customer with the portable two channel amp is glad he has chips in his amp because he can afford it, it works well, and does not weigh much.