Sub hookup in a 2ch/HT system with preamp passthru

I have the same setup as you:
a preamp for 2 channel with HT passthru and 2 outputs, a separate surround processor and one subwoofer. I agree with Kr4 above and set up my system the same way. The key is setting both L and R front speakers speakers on the processor to 'large' and the subwoofer to 'none' - this will direct all low frequencies to your front channels, which your subwoofer is a part of. You can then set the crossover on the sub to your liking. I find I like the crossover lower (40hz)on music and a little higher with movies.
Also, you can set your center to 'small' if you'd like to direct center channel low frequencies to your mains and subwoofer.

Thank you fellas for your help. I really didn't want to use a sub BETWWEN my pre and amp since I'm using XLR's (Aqueous Anniv. from Purist) between preamp and amp. THe amp is 2 channel and accepts either RCA's or XLR's. Can I not go:

2 channel - source with XLR's > preamp > output with XLR's to amp. I would use a pair of RCA's outputted from preamp (I have main, output1, output2 pairs in RCA and XLR as outputs on this preamp) to subwoofer in (RCA L/R)

When in HT can I not just take a y-cable with 1 RCA out from SUB OUT on the processor and input into any pair of inputs on the preamp. I don't know if the preamp (since it is in passthru mode at this point) will pass the sub signal through as well. As it is now the front channels (L/R) come out of the processor into the preamp's 2 AUX inputs. Can I not just Y from the processor to another set of inputs on the preamp and the signal will work in HT? As an additional note, I CAN switch OUTPUT 1 and OUTPUT 2 on and off manually or remotely but on the MAIN preamp outs I cannot. Any other options guys? Might have to send the unit back and buy the new REL Britannia 2 which is inputted right from the speaker outputs on my 2 channel amp and could connects right to the processor via 1 cable to get the .1 in HT. THanks very much for taking time to correspond. Velodyne thought I was a freak when I mentioned my setup (2ch/HT hybrid) to them and didn't have anything valuable advice to add. Thanks. Dave

Your stereo preamp cannot do anything with the SUB OUT if you are using it for L/R. It is only 2 channels.

The only other suggestion with your present equipment is to use the sub only for HT and not for stereo.

Kal

Well guys here's the method that works and no need to connect using the speaker out on the sub.

2 channel - paired RCA's from preamp out to sub in. No problem here and I can save a 2 channel preset with this sub. Can also switch sub on and off from preamp (OUTPUT2 in my case)

HT/Satellite - Simply run a Y-cable from the processor SUB OUT single into any pair of inputs on the preamp.(In my case I used the TAPE, but all inputs work). I know the sub signal still passes through another component but it gets too tricky doing the other methods. I can still use the crossover from either the pro or the sub in this case and can also switch the sub on/off with the OUTPUT2 button on the front or the remote. Can also save a preset for HT and satellite in the sub's memory to default there even time HT is needed.