Yes it does add jitter, it does save a few cycles .

I wanted to thank everyone for their help. I got a bit distracted form this project for a few weeks but implemented the changes suggest by Chromatix and it works quite well. The number of cycles though each path is also very close. I started producing a video about playing DIGIs on the C64 which I hope to finish up this weekend.

Yesterday I had an idea of how to implement an interpolating scheme. Hopefully resulting in a playback quality very similar to the 8kz sample rate but with half the memory footprint. I'll start a new thread on that subject though.

This relies on V being clear and Y is clobbered so maybe not so good when it comes to debugging.
I think it's 7.5 or 8.5 depending on zp or not.

Personally, I prefer using "LSR flag" instead of "ASL flag".

The reason being is that in the initialization routine, there is almost always some register set to zero and it will save 2 bytes as an extra instruction to load the $55 or $AA is unneeded. For me, it is not only just about saving bytes but also saving bits as only the 0-bit and 1-bit ever comes into play.

LSR flag
BCS next:
INC flag
...
RTS

next:

will work just well.

Also note that if the carry needs to be preserved when entering a routine, the

LDA flag
EOR #$80
STA flag
BMI routine2

might also be the better option