Centaur sound question.. AY3-8912

[Phil Lee]

So, no sounds initially on Centaur - but a little speech.. I'm mid building the 'Big Clive' SIA (Say It Again) replacement, but doing initial checking / reflowing / repinning the sound card, I noted theat U12 was empty.. schematic says sound generator AY3 8912. Aha says I, missing - so orders one of the more expensive PCB insects.
However after going through the whole board, i plug in and everything seems to be working? Background sounds (previously missing) appeared - before the ordered chip even arrived!
So am I right in thinking the AY3 sound generator is not needed for Centaur? Found conflicting accounts on t'internet, so thought I'd pop a question here..
Schematic error or owner error?

 

[pinballmania]

U12 not fitted. You’ll see the links below u12 labelled EE are fitted which bypasses the missing device.
Check the two potentiometers on the board as these are prone to going open and cutting off either sound or speech. On my own centaur I put a link over these and bypass them as I don’t feel the need to balance sound and speech.

 

[Phil Lee]

Many thanks for the pointers.. much appreciated..