2. amps-preamps
  3. 1422229160

How to split a signal to inlcude subwoofer?

I think that my question is most simply stated as a 'how to' split signal issue. My setup is pretty simple. It starts at a tube pre-amp. The

pre-amp has 3 pairs of rca plugs that allow me to input 3 sources. CD player, Blue Ray connection and a direct to smart phone input. My problem

and/or question stems from the fact that I have only one output pair of l/r channels exiting the pre-amp. I have 2 power amps that I split the

signal by going through the equalizer/splitter that comes with a pair of Bose 901 speakers that I am NOT using in this setup. This seems to work

very well to solve the problem of outputting to 2 amps, and then 2 pairs of speakers, but I have a powered subwoofer that I want to add to the

system. I have tried by using a cheapo Radio Shack splitter where I have one line in then it is split into 3 lines out. 2 for the amps and one

for the powered subwoofer. It really degrees the signal and I end up with an unacceptable sound. The pre-amp does not get enough of a signal to

be heard.

I know that the Bose 901 Equalizer is not made for this application since the speakers it was made for are not being used but It seems to be

working pretty well for now for splitting the signal between the 2 amps.

Any suggestions on what I need to do to get a reasonable signal out to the subwoofer? Probably the simplest solution would be to get a different

pre-amp but I am really hoping to keep the primitive tube pre-amp that I am using now. So bottom line is I want to know if there is any way I

can continue using my current pre-amp with only 1 output out and get a decent signal to my subwoofer.

Thanks very much,
Jim Lee
sasjzlee
arh
366 posts
 
Why not use a good y adaptor like from Cardas. I use one in my system to feed a sub and it sounds excellent
Alan
mesch
3,484 posts
 
If your sub has high level inputs you can wire it from the speaker binding post of the amp driving the speaker pair to which the sub is to be included. The very high input impedance of the sub will not draw power form the amp when wired this way.
almarg's avatar
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almarg
9,670 posts
 
If the sub does not provide speaker level inputs, or if the good suggestion by Mesch is not feasible for any other reason, let us know the make and model number of the preamp, the sub, and the two amps. Hopefully we will then be able to determine the output impedance of the preamp, and the input impedances of the sub and the two amps.

Also, let us know the approximate length of the cables between the preamp output and each of the other components.

I'm not sure what is meant by "the pre-amp does not get enough of a signal to be heard," but assuming that the problem is poor sound quality coupled with a slight to moderate reduction in volume the cause is likely to be that the combined impedance of the sub and the amps or equalizer is too low to be driven properly by the probably high output impedance of the tube preamp.

The line-level input impedance of powered subs is often very low, in the 5K to 15K area in many cases. In combination with the input impedances of the amps or the equalizer the overall load impedance seen by the preamp will be considerably lower than that, which would be too low for many tube preamps to drive with good results.

If so, and if the sub does not provide speaker level inputs, you would have to either replace the preamp, or insert an active buffer stage providing low output impedance between the preamp and the other components. A high quality active buffer stage is likely to cost a few hundred dollars or more. The least expensive buffer stage I am aware of is the Yaqin SD-CD3, which various sellers offer in the area of $175 to $200 or so. I have no idea as to its quality, though.

Regards,
-- Al
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