Ubuntu sound changes, partly to myself

Before 18.04: I could use pavucontrol to have the input of the sound card be the same as what it is outputting = ideal for recording audio streams. The actual output volume level to the speakers didn't matter - even with the sound turned down, it would record 'loud' sounds sent to the card as 'loud'.

With 18.04: I still can, but the system's output level now does affect the recording.

Was there a change in pulseaudio?

The other thing that's changed since I last did it is that it's no longer the same PC with a sound card, but a new one with a motherboard chip doing the sound. I wonder if that makes a difference.

(I now can't remember why I put the sound card in the old one - did it give better results than its onboard sound? Ah, or did the old one not originally have Windows 7 drivers for the onboard sound?)

Update: on JA's - also running 18.04 - the system's output level only affects the recording if it's muted / set to zero.