How to use Line6 lowdown 300 as a power amp with other preamp?

I have had a combo which is line6 lowndown 300.And I have bought a amp which is eden wtx550 recently .
Now I have no anyother speaker cabs.So I want to use my eden wtx550 as a preamp and line 6 ld300 as a power amp.
I can use the phone or effect send to output the signal ,but I can't find any signal input port in LD300.
I don't want to input the preamp signal to its normal input port,I want to skip the preamp circle in LD300.You know ,LD300's preamp is having so many pollution to input signal .
How I can use line6 ld300 as a pure power amp?

 

you mean I can use this jack to input the preamp signal?it need a transformer for 6.5mm to 3.5mm.