Subwoofer for classical music listener

+1 Al


I don’t recommend splitting line level signals or long line level runs from consumer gear to the amp unless you happen to have a rather powerful preamp like professionals would use. Consumer hifi is usually underpowered and can sound lifeless in situations driving multiple loads simultaneously or long runs. In any case low capacitance wire is best and given the high impedances ideally you would want low noise interconnect like Canare star Quad wire (to protect from EM interference or audible hum from transformers or AC power). So to add to all the excellent advice from Al - try to ensure you have the lowest capacitance wire you can find within reason - Canare L4E6S would be my choice.

If you are using RCA rather than XLR then you also have a higher chance to get hum with shared line levels (due to ground loops).

Also high impedance inputs will make equipment more susceptible to ground loops. (47k is five times that of 10K impedance and ground loop noise will be commensurately 5 times higher - because ground loops or EM noise has very little current the higher the impedance seen the more noise you hear as the small spurious voltage dissipates less into higher impedance. This is why pro gear can often have beefier preamps and double the voltage output (XLR) and lower impedance devices can be connected to them - it makes the system as a whole have greater noise immunity)

Shadorne, thanks for the excellent comments. Regarding cable capacitance I’ll mention that I had raised that issue earlier in the thread, and it turns out that the OP’s existing interconnects are only 2 feet long. Given the preamp’s nominal output impedance of 500 ohms, and assuming the length of the cables to the sub is not unusually long, cable capacitance (which of course is proportional to length) is therefore unlikely to be an issue in this case.

I’ll mention also, as I’m sure you realize but others may not, that the capacitance of the cables connecting the preamp to the sub can affect what is heard from the main speakers just as much as the capacitance of the cables connecting the preamp to the main power amp. The reason being that the capacitance of the cables to both destinations will interact with preamp output impedance and thereby affect the signals that are present at the preamp’s output terminals, that in turn are sent to both destinations. The resulting effects, if any, being most likely to occur in the treble region.

Bob, in answer to your questions I would put it that induced noise can typically be viewed as emanating from a high source impedance. Therefore the lower the load impedance the more the noise voltage appearing across that load will be attenuated, due to the voltage divider effect that will occur between the load impedance and that source impedance. And since the receiving device presumably responds to the voltage appearing across its input impedance, that voltage (and not current) is what matters.

Best regards,
-- Al

I owned REL Storm III and loved it. I tried line level and speaker level connections. I really liked what the sub could do for my system. Bought a measuring mic and learnt how to use REW. So I could measure the impact of varying  placement.

Later I bought 2 Rythmiks 12" kits and built sealed, very heavy (100 lb each), rigid boxes. For less than the REL I got better sound. Rythmiks are servo driven and also have a lot more controls for fine tuning. It was a lot better than the REL.

Eventually I went from the pre (Lamm LL2) to the subs xo and from there to the tube power amp, relieving the amp and speakers from attempting to reproduce below 80Hz. Yet another improvement. Like the article linked to earlier said. 

If you extrapolate the reasoning in that article you arrive at an active system. Later I did without the preamp altogether  abd went active. Running digital xo at the software level, adding time alignment of the sub and midbass woofer, and adding room correction is yet another leap forward. Despite this being a paradigm shift for most audiophiles thinking digital xo are detrimental. I know I'm not going back.