TDA7269A RL output RL inductor after Zobel, or not...

[Roman4]

I plan to design active speaker amps with TDA7269A (single ended), these use zobel R+C at the output for stability reasons as per datasheet. But I was thinking to maybe also include RL output inductor in series to the speaker after zobel as it is often common. Appliance is a regular home use. Datasheet do not mention this and so I wonder whether this would add or even subtract to/from stability, or be just completely unnecessary. AI had a good point that internal IC compensation could take this into account(no RL) and I could only worsen things by adding it, though I often read on internet that this is often just to appear more attractive and RL should be always added etc. I know for example that STA540 specifically mention and explain why even regular RC isnt needed but here I dont know. If someone especially from design department or someone who know for sure would be able to answer, I would really appreciate it. Thanks

[AScha.3]

Hi,

The RL is useful, if speaker with strong capacitive behavior, like electrostatic speaker, are connected.

It limits the effect of the capacitive load.

So if you don't do this, also not using high capacity cables on the output, it's not needed.

[Roman4]

Thank you, but I would like to know deeper about chip itself, how the chip compensation was designed(STA540 does explain it better for example), how far into capacitance without inductor is stable and most importantly whether inductor itself may affect stability since there is none in datasheet and could perhaps interfere with IC internal compensation etc. I will not use specialized electrostatic speakers but I will certainly use twisted cable, ~2 meter long. Cable twisting lower inductance and increase capacitance by some amount depending on twist granularity.

[AScha.3]

>but I would like to know deeper about chip itself

That will probably remain a wish...

But from my experience:

- why you choose the TDA7269A ?

I just (also) decided to build a active speaker , so i choose a bridge amp , only one supply needed, and asymm IN and symm OUT , for low influence of ground problems : TDA7560 , 4 x 20W ( 4 ohm) at 14V supply (i will use about 15..16VDC ).

- about cables: 

I tested a lot with cables...and at the end decided, to put together, whats in physics about conductors, see:

https://stromrichter.org/showthread.php?tid=4502

Then try and listen...

so i would recommend : NOT twist the wires, thats a bad idea (soundwise) . And dont use "heavy" good litz-wires.

Just try a simple, solid, clean copper: maybe strip a CAT7 installation cable, solid copper, 0.8mm, and have the +/- lines separated > 20mm , to reduce proximity effects; just glue the cable together using some (PE) foam , the 0.8mm CAT wires, and some adhesive tape. Try it...might surprise you, sound wise.

[Roman4]

Thanks for an interesting article! Reason I go with TDA7269A is because it fit to my other needs. I do not design active speaker but an amp with active crossover and usb dac in one. It will be powered by dual supply which I already have, so that can be used for all circuits. Some amp will have a dual function to be used by regular stereo speakers, or I will have one more extra for that. Speakers are in 10W range and mid one have 4 ohm while others 8 ohm and 89db instead 90db, this mean i want neg. feedback control to match gain as I need. TDA7269A (3x or 4x) is a good match for that. I only need good confirmation about output inductor vs stability and then I am good to go. 

Twisting cables in general is one of the most important and recommended practices, you dont want your cables to be antenna! And not only speaker ones, but also small signal and transformer/power supply wires: https://hifisonix.com/wp-content/uploads/2019/02/Ground-Loops.pdf 

Anyway thanks for all help, I will open ticket directly and ask them.

[AScha.3]

Ok, 

but > Twisting cables in general is one of the most important and recommended practices

is absolutely correct inside amp , or close to transformer, to avoid magnetic pickup,

but a (long) line to the speaker is a different thing. (Believe me. Or better: try it and compare.)

+

>I will open ticket directly and ask them

Thats what i would recommend here also. :)