mirosol wrote:First, would lowering the values for R3, R4, R15 and R18 help with the output level issue?
Second (as i couldn't find my answer in the datasheet), does the chip suport simultaneous rec/play with different samplerates? You probably guess where i'm going with this

Yes, the output could probably be raised by lowering those resistors, but the sweep of the tone would suffer.
I'm working on a revision with a different kind of tonestack (with less volume loss) and a makeup gainstage insted of the buffered Vref (isn't really needed).
It will overall have less components and be able to be quite a bit louder than unity.
The chip is a single message chip, so it's not possible to do simulanious playback and recording for overdubs/bouncing.
That would require two chips. I'm actually working on a two chip version already.

The tricky part is to have both chips controlled in a logic fashion, perferrable sharing controls.
Setting up the controls for one of these chips was hard enough, as I had to use CMOS flip flops with switch debouncing.
The most annoying drawback of these chips is that they always powers down into a powersaving state before beginning playback again, so fluid repeats is not possible.
There will always be a short (like a half second) delay between the repeats.