Re: Pinouts for TI speech ICs

..... but getting back to the TMC-0281 (speech synthesis chip). I
believe this is the one I need more information about as I'm trying to
create an audio line-out from the Speak & Spell compact (which uses a
piezo-speaker).
According to the schematic I found on some forum (since that forum was
closed to non-members I've uploaded it here so you can follow what I'm
talking about:
http://home.c2i.net/w-460389/speak_spell/Speak_Spell_schematic.gif)
pins 11 and 12 handle the audio output. But there's some inconsistency
as the quality doesn't improve even after cutting the traces to the
rest of the circuitry and feeding pins 11 and 12 directly into my
mixer/amp.

Since the regular Speak & Spell uses the same speech chip I thought I'd
see what would happen if I did the same thing with that toy, so I cut
its traces from pins 11 and 12 and fed the audio directly into my
mixer/amplifier. Same sound as I've always heard it (and so much
cleaner and better than the Speak & Spell Compact). Very strange.
Could it be that the "shaping" (filtering/adapting etc. for the
piezo-speaker's limited frequency characteristics) could be done
*before* the output stage?
That would explain things.

Another thing... I just had a look at both circuit boards and I have to
correct something I said above. The TMC-0281 are *seemingly* the same
in both toys, but when I look closely I find the following markings on
the ICs:

First, the "Speak & Spell":

TMC0281NL
WA 8114
Philippines


Then the "Speak & Spell Compact":

TMC0281D-NL
ME 8149
Philippines


I assume that the numbers/lettering in the second line are just
production numbers, but in the first line there's a "D" suffix in the
Speak & Spell Compact's chip. Could this denote a different version of
the chip, or just a production run or something?

If the chips were socketed I could simply exchange them and see if
there would be any difference in audio, but I'll have to de-solder them
(28 pins) if it should come to that, so I'd like to hear what you all
have to say about it first.

.

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