op-1 and external mixer

Hello, I tried to connect op-1 as a synth to external mixer via 3.5mm => rca cable. But sound level was very low, even with full volume up on op-1 and on mixer’s track. What I did wrong? Is a preamplifier necessary?

Did you remember to crank the white volume clock fully clockwise too? I haven’t had any issues, used the OP-1 with many mixers.

check your master levels on the master drive screen?

orange level on tape too…? tape track levels?