Need some advice from soemone more knowledgable than myself here. I have a pair of tube monoblocks powering m80's, along with a tube preamp with two outputs. Recently came across an HSU STF-2 subwoofer that I'd like to add to my 2 channel system. I'd prefer not to use the <input from amp/output to speakers> connections on the back of the subbecause I think I might lose soemthing from my monoblocks, but the subwoofer only has a single rca "sub-in" jack. What's the best way to use my second set of outputs on my preamp to use this single sub-in? Can I just use either the L or R output from the preamp to the sub in, or may be a Y connector to join both L & R into the single rca sub in? Or should I just be using the speaker connections? Any advice would be appreciated. Thanks alot

Simply plug the RCA plug from your preamp output to the mono imput on the subwoofer and you will be fine.

Thanks for the quick response, koiman. Just to make sure - are you saying to use either the left OR right preamp output to the mono subwoofer input?

Correct.. the subwoofer is a mono amp so it dosen't make any difference which output right or left that you use on the preamp.. Hope this helps..
Lee

Scott, welcome. If you want to use the pre-outs instead of speaker wire from the amps, then yes, you should use a Y-connector at the preamp so that the sub will get both left and right channel information when the two differ. Incidentally, though, if you'd run speaker wire from the amps instead, the sub would use essentially none of the power from the amps because of the very high input impedance(10,000 ohms or more)of the sub amp. The wire could either run from amp to sub and then out to speaker or simply run parallel wires from the amp terminal to both the sub and the speaker.

Scott, a further point is that if you want to avoid the possible interference between the left and right preamp outputs which concerns some and don't want to get into more complication in doing so, the speaker wire connection(either of the two methods)is simpler.

Thanks for your messages John. I followed your advice and used the speaker wire inputs and then out to my m80's - hooked it all up this morning and am now in the process of fine tuning. Sounds great, but needs some tweaking. Getting some weird kind of tinny distortion on the real loud highs with vocals as if the tweeters can't handle it.
Hope this all resolves.
Scott

Just out of curiosity, why are you not using the sub out jack from your pre or receiver?

John, the problem that Scott had was that he was using a stereo preamp with no bass management through a sub output. There was a second set of L/R preouts which he was thinking of using, but the STF-2 has only one line-level input, so the two preouts would have had to be combined in a "Y" arrangement to get all the information from both channels. There are some views that this shouldn't be done with a simple Y, but that a circuit to prevent any interference between the two channels should be part of the Y. Note this article which Rick(wid)brought to my attention. I still question whether the problem is serious enough for this complication. In any case it would be just as simple for Scott to either run speaker wire to and then through the sub to the speakers or the alternative of parallel speaker wires from the amp terminals to the sub and directly to the speakers.

Got ya and thanks. I didn't realize we were talking a stereo pre here.

Thanks for all your advice guys! I had to run out of town for a few days but did manage to hook up the subwoofer with the speaker wire connections just before I left and things are running well now.