Change the sound of "to" to "dA"?

I am studying Barron's American Accent training, she said" I'd like you to all "to" to "d+schwa", except "to" in the beginning of a sentence. Is this correct? She also gives 3 examples:

He had to do it.
He got to do it.
To be or not to be.

I would disagree. (Are you familiar with IPA? If not, see this article: http://en.wikipedia.org/wiki/X-SAMPA .)

In the first example, I would pronounce "to" with a plosive [t]: [hi hæd tə ˈdu: ɪt].

In the second example, I would likewise use a plosive [t]: [hi gɑ:t tə ˈdu: ɪt]. Using a [d] there would sound totally unnatural.

In the third example, I would likewise use a plosive [t] in both instances: [tʰə bi: ɚ nɑ:t tə bi:]. Again, it would sound totally unnatural to use [d]s there.

I would say that in General American English, "to" uses a flapped [ɾ] (which is a more accurate description of the sound than [d]) when it's unstressed and follows a vowel, and (sometimes) when it's unstressed and follows /l/, /n/ and /m/.

Same here, as in:

"He had to do it." [ˈ(h)i ˈ(h)ɛ̞ːtʲːəː ˈdʲʉ̯u ˈɪʔ]
"He got to do it." [ˈ(h)iː ˈgaʔtʲːəː ˈdʲʉ̯u ˈɪʔ]
"To be or not to be." [ˈtʲʰʉ̯u ˈb̥iː ˈɔːʁ ˈnaʔtʲːəː ˈb̥iː]

<<I am studying Barron's American Accent training, she said" I'd like you to all "to" to "d+schwa", except "to" in the beginning of a sentence.>>

I read that course too, and I noticed some major nonsense in it. That's one of the things I would take as bad advice.
What I noticed is "to" can always be pronounced with an aspirated t (normal pronunciation), and it often becomes "d or tapped t + schwa" in connected speech after voiced consonants or vowels.

I need duh do it.
I should be able duh do it.
Move duh the left.
Try duh avoid junk food.

That's not mandatory though, because I have noticed many people use the "normal" aspirated "to" in all cases when trying to speak clearly, slowly, formally, or not continuously.
I am not sure about "had to" though. It is idiomatic to pronounce the forms of the verb "to have to" as "hafta" and "hasta", so you have a devoicing... How about "had to"? Is it always "hat to", devoiced as well?

I, personally, would say "da" in all of those sentences, upon reflection.

I think of it as "hadta".

I think I will use "to" as a flapped "t" + schwa, that will work, except in the beginning of a sentence.

2:43 (they had duh do it)

http://www.youtube.com/watch?v=KntmpoRXFX4

So I don't know which way it more common. Either "hat tuh" or "had duh".

none of those are right. "had duh" doesnt even sound like american english. i think they confused "duht(to) with duh as in the.
"dah teacher said so."
"dah book is on dah floor."
although these are highly informal. i advise you to stick with normal speech until you move to a certain place and pick up on thier way of speech.

Lazar,

What Nick is asking doesn't have anything to do with the link you provided. It's not about IPA .
What this lady is trying to say in that course and others as well, is that when American English is spoken at the "fluent level" some short words (usually prepositions) are missed or when inbetween vowels there is a letter added to. Like in "did you" you hear the "dj" sound.
So, in conclusion, the book is right.

<<So, in conclusion, the book is right.>>

No, I think the book is confusing and wrong because it gives bad examples. In "To be or not to be" I think both of those "to" have aspirated t's for all native speakers.
In "he had to do it" though, you have the "to" particle after a voiced sound, so the T can turn into a tapped T or a D (Example: "I need duh do it"). However, I was not sure about "had to", because it's part of the idiom "have to", which is pronounced differently than expected (hafta, hasta). So, HAT TUH or HAD DUH, that is the question. I recently paid attention to that and heard a couple of HAD DUH (see video), and no HAT TUH. Maybe both are possible.