Subwoofer connection to older tube amp

Use the sub amp and save the power from your tube amp for speakers only. Your tube amp might not like the load if you hook up speaker wires to speakers and sub. You can run line level to the sub and then line level out of the sub to your amps.

The other way to do it would be to use a Y spliter cable coming out of your pre-amp. Run line level to the sub and another to the D-90 amp. you can also buy rca splitters that are machined out of a block. Audioquest makes one.

http://www.nextag.com/AudioQuest-M22FHRD-One-Piece-79384484/prices-html

As explained to me by the main tech at HSU, the builder of my sub, the second set of speaker cables going to your sub from the main speaker terminals aren't drawing any appreciable power, they're just picking up frequency and amplitude information to be amplified by the amp in the sub. He said the gauge of the cables going to the sub doesn't even need to be the same as your main speaker cables since they're carrying very little power.

Thanks Sfar. If I can just run parallel wires off the same amp out connector that sounds easiest.

I appreciate Steuspeeds directions for using the line level outputs but as long as there isn't a real power drain on the D-90 and the sub amp is being used I'll do the joint speaker wire set-up.

That is how the high level inputs on a car stereo amp work for head units with no pre-amp out. It should work ok then. The down side is that the signal is amplified by the D90, un-amplified and re-amplified by the sub amp. This is likley to produce muddy bass. For best fidelity use direct rca line level connections with splitters like the Audioquest.

OK, but I'm still not sure what line level connections I have on the pre or the amp. The pre may have those but the amp really just has screw posts for speaker outs at different ohm levels. The only RCA style inputs is the Main for the pre input.

The sub has RCA line levels connections but not sure about these older tube electronics.