The (high-cap.) unregulated PSU for chipamps

[Cobra2]

-but did not do much experimenting...just added 220nF & R.
BTW, tried different resistors?

Arne K

[carlosfm]

Originally posted by Cobra2
-but did not do much experimenting...just added 220nF & R.
BTW, tried different resistors?
Arne K

No, just 1 ohm.
I think it's better to deal with one component at each time.
Maby there's more to test, and more to improve, any beta testers out there?

[Cobra2]

I was more thinking of inductive vs non-inductive resistors...

Arne K

[carlosfm]

Originally posted by Cobra2
I was more thinking of inductive vs non-inductive resistors...
Arne K

That is a really good question.
Carbon (or film) resistors is the way to go, no bobinated resistors here.
I'm testing with a 1 ohm 3w resistor, although I think that two 2.2ohms 3w in parallel would be fine too.
It's recommended something from 5 to 10w.
3w carbon resistors I can find easily.
More than that is not so easy around here, only bobinated.
I could order (more expensive) film resistors, but for test purposes it's carbon.
And it works fine.

[ChuckT]

Very interesting.
Does the small value RC bypass include the small cap directly across +/- pins on the chip?

[matjans]

since i've built my ucd180 based class d amp i've got a few gc's laying around doing nothing. i think i'll give it a try.

How much influence do the small caps have that are soldered to the chip? In all of my current clones these are ~1000uF panasonics or black gates. Do i need to replace them with smaller value ones?

[carlosfm]

Originally posted by ChuckT
Very interesting.
Does the small value RC bypass include the small cap directly across +/- pins on the chip?

I'm not using it on this LM4780 board, due to lack of space (and the crazy pinout this chip has), but with LM3886 and others I normaly use 270nf poly between + and - pins on the chip.

[carlosfm]

Originally posted by matjans
since i've built my ucd180 based class d amp i've got a few gc's laying around doing nothing. i think i'll give it a try.

Do it.

Originally posted by matjans
How much influence do the small caps have that are soldered to the chip? In all of my current clones these are ~1000uF panasonics or black gates. Do i need to replace them with smaller value ones?

Yes, after the snubber there should not be big caps.
It would defeat the snubber's job.
100uf is what I use on the chip.
Alas, what works fine with regulated PSU also works fine here.

[matjans]

obrigado, amigo

[Upupa Epops]

To Carlos : All what you now discover, you may to see on my 4780 PCB .