New system/room, upgrade amp or preamp first?

04-24-15: Toddrhodes
I will throw this out there, just to get feedback - am I loony for thinking a simple single-ended Y out of the preamp would be doable until I (ideally) find a balanced amp so as to use enable both sets of outputs concurrently? Not dismissing the high-level input option, just curious.

Not a loony question at all. In fact, given the 50 ohm output impedance that is specified for the Pre1, I suspect that would work well, if perhaps not completely optimally. (I'm assuming that the sub can accept an input covering the full frequency range for at least one of the two positions of the switch I referred to earlier).

One thing that has to be considered with respect to that approach is the possibility that the combined input impedances of the sub and the power amp may be too low for the preamp to drive with good results. Particularly because the line-level (RCA) inputs of most powered subs tend to be low. There doesn't appear to be a spec on that for your BIC F-12 (the 8 ohm "input impedance" value that is indicated would be for its driver, not for its amp), but I wouldn't be surprised if it were in the 5K to 10K area. The combined parallel impedance of 5K and the 33K input impedance of your amp would be (5 x 33)/(5 + 33) = 4.3K. That would be too low for many preamps to drive with good sonic results, including some solid state preamps, most tube preamps, and probably all resistive-based passive preamps. But it shouldn't be much or any problem for the Pre1, given its 50 ohm output impedance.

A second issue that should be considered is the ability of the preamp to drive the combined capacitances of the cables to the main amp and to the sub, without perceptible rolloff of the upper treble resulting (the capacitance of the cable to the sub, as well as the capacitance of the cable to the main power amp, can potentially affect the high frequency content of the signal to the main power amp). The likelihood of that being a problem increases in proportion to the output impedance of the preamp, to the lengths of both of the cables, and to the capacitance per unit length of the particular cables. For most reasonable cable lengths and cable capacitances an output impedance of 50 ohms is low enough to make any such issue unlikely.

Finally, ground loop hum is a conceivable issue, but I suspect that the chances of that occurring with this configuration would not be particularly greater than in most other situations involving unbalanced interconnections to a sub.

Good luck. Regards,
-- Al

I've learned more about audio in general, and system considerations to a more specific degree today than any single day I can remember :) You are a very kind person to spread the knowledge you have to anyone willing to take it in. Thank you Al.

Todd, 87dB is middle latitude sensitivity. Hope the BC pre proves to be all you hoped for. Al is a great asset here, I have learned much from him. I have considered the use of Y splitters also and knew of reactance issues however with now a better understanding. Thanks to you for your thread and again to Al.

Todd and Mesch, thanks very much for the nice words.

Regarding my earlier comments about connecting subs at speaker-level to amps having balanced or bridged outputs, I should add that it is often (although not always) possible to accomplish that. As I indicated, the negative input terminal of the sub should not be connected to the negative output terminal of that kind of amp. But connecting the negative input terminal of the sub to a chassis screw on the amp will often work well, depending on the amp's internal grounding configuration.

Also, there are some cases where the amp provides a circuit ground terminal, and connecting to that would work. Or if the amp provides both XLR and RCA input connectors the sub's negative input terminal could be connected to the ground connection of a connector that would mate with whichever of those inputs is not being used.

But my point is that there may be some cases involving amps having balanced or bridged outputs in which there is no practical solution for connecting a sub at speaker-level.

Best regards,
-- Al

I would go with the preamp first as I feel thats the foundation of a system. I would spend the most I could as I would like to keep if for a while. I don't think you can do it new but used, with some help, you can have some fun. I'd be willing to help with a really good price I would give you on an older Innersound preamp. Check it out on line )now sanders sound). It was $4 grand new and is solid state, black as night and makes the grand canyon seem narrow. dynamics are awesome. It gets out of the way so you can hear everything else. If you're intersted, I will make you an offfer you can't refuse.