As I mentioned earlier in this thread a Covox Speech Thing clone, the "SoundJr" uses:
"767163103 and 767163203, or 8A103 and 8A203 surface mount resistor array ICs"
and it has the following features:
"Level Control: 20 dB/ 8 Step software control
Frequency range: DC to 15KHz
Sample Rate: Set by software, typical 100s/s to 20Ks/s, 100Ks/s max.
Digital Code: 8 bit Linear PCM + 3 bit range"
It has roughly double the frequency range of the discreet R-2-R ladder Covox design, as well as volume control, and runs strictly off of LPT power.
I can say with certainty, the sound output is very nice as well as clean.
I would say, without a doubt, the SoundJr. resistor array IC design is the pinnacle of the Covox Speech Thing's potential. I don't think one can do better than a surface mount resistor array IC, as far as integration and simplification of components and design.