pre amp output

Is this normal
Using the 60hz audio file from home theater shack I measured the audio output from my onkyo intgra tx 870
And found it to be 10.4vac at maximum volume. I am feeding this into a ART 355 EQ then and setting the maximum voltage to 1.2 vac then into a rane SM26B splitter/mixer. From there I adjusted all the outputs to 1.2 vac.
I am then feeding back into the onkyo main ins and Yamaha p2100 amp, kenwood km209 amp, and two jbl 300 watt subs.
Each amp only drive one set of polk audio monitor 60 II’s.
It sounds good but that high pre out voltage from the onkyo scares me.

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What is the pre-amp input V?
It is common that a pre-amp ( tone-controls defeated) has a line level input of 150mV and an output of around 1V, giving a voltage gain of 1/0.15 = 6.66 or 16.5dBv.
Sounds like an ouput of 10.4Vac is getting close to the pre-amp clipping limt!! so your input signal I would guess to be 10.4/6.66 = 1.56 Vrms, need to measure this to confirm the actual pre-amp gain. Make sense to you?