Yes you can use a regulator to regulate that down to 9V. Just use a big heatsink.
I'd suggesting using a LM317HVT <--- note: HV type
You probably don't want to use DC/DC switching regulator here as any EMI/RF noise may travel back to your mixer and may be heard as noise.
I said MAY because in general, the CMRR of your preamp should take care of that noise and you won't even hear it.
But who knows.
The max. voltage differential (Vout - Vin) of the LM317HV type is 60V. So you're okay*.
- Just use a big heatsink because that will be dissipated as heat.