- Joined
- Dec 12, 2019
- Messages
- 13,603
- Likes
- 30,326
This might seem technically unsophisticated ("brute force") but it's absolutely true. A pair of simple Y-cables will work fine to split the output (e.g., from that little box of SchiitOr you could just split a single set of outputs between sub amp and power amp too. Most subs don't have a crossover and neither do many 2ch pre-amps/amps like this.
Here's my little powered subwoofer, e.g.

In full disclosure, there is a second 15" driver mounted on the bottom side of the enclosure as well - not visible in this photo. The amp/XO/DSP is a modest little Dayton Audio Class D subwoofer plate amp seen sitting atop the subwoofer in a rough 'n' tumble "enclosure".
I feed the subwoofer from a pair of paralleled unbalanced outputs from my little TVC (transformer volume control) attenuator/switch box, while feeding the other pair of outputs to the amplifier.


Note the three pairs of stereo unbalanced line level inputs on the left and the two pairs of stereo unbalanced line level outputs on the right in the lower photo.
In practice, things today at my house are configured in a bit more complex way than this -- but I used the system for years without any further complication than as described above (i.e., with no active preamp stage at all).