"Arny Krueger" wrote
"Fleetie" wrote in message
...

In the real world, the output from the D-A converter running at 30kHz
(remember Nyquist) will not be a 15kHz sinusoid, but will be a 15kHz
square wave.

Absolutely and totally wrong. The output of any proper DA is a smooth wave
with no square waves related to the sampling frequency.

ARE left with a 15kHz sinusoid again.

A DAC that lacks such filtering is not a proper DAC, which is why its wrong
to say that a DAC has a square wave output.

I disagree, but it's semantics.

Depends what YOU CHOOSE TO CALL A DAC. I'm talking about it
stopping at the digital part that switches the resistors/
voltage divider/whatever (not over-familiar with the innards
of DACs).

I suggest you review your zeal to "look cool" by disagreeing
with people as forcibly as you can, in favour of an attitude
more closely allied to the facts and theory being discussed.

If (as may well be the case, and as makes perfect sense)
real-world "DAC" chips in fact do incorporate such filtering,
then well and good. It removes the need for the user to add
this filtering themselves.

BUT STILL, WHAT I WROTE ABOUT THE SQUARE WAVEFORM STILL APPLIES
SOMEWHERE INSIDE THE DAC, I WOULD IMAGINE, SO MY EARLIER STATEMENTS
ABOUT THE ADDED HIGHER-FREQUENCY "NOISE" NEEDING TO BE REMOVED
ARE CORRECT.

Oh, and I'll have fries with that, cheers Arny.

--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk