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Wiring confusion with JL sub and components

I'm hoping some of you can offer more help than I've been getting from JL Audio. I've had one of their wonderful Fathom 113 subwoofer for a few years now and don't believe I've ever had it correctly connected to my designated 2-channel system.
I have an older Jolida 801 integrated tube amp which, because I am running a Jolida JD9 phono preamp, new SACD player (just scored on one of the new Marantz SA 11s'), along with a tuner, doesn't have any remaining RCA connections to be able to connect the JL sub to my Tape connection (have seen this as being one of the suggested methods of connecting). I had purchased this power source used around 6 yrs ago. The previous owner had an additional set of RCA connectors installed for running some sort of sub within his system. I've come to find out that these 2 connectors won't work with my JL Sub, so this is why I'm posting a question out to you folks.
Other than purchasing a new amp/preamp setup or running this sub off of my "normal" speaker "outs" is there a better way to connect the Fathom to my Jolida? I'm starting to see where I'm pushing myself beyond the usable parameters this Jolida offers, but can't afford to chew off 8grand until next year. Would like to see what correct methods of integrating the system together might be. The Jolida does have both 4 and 8 ohm speaker connectors on the rear. Not sure if these connectors would be worthwhile or not.
By the way, my main speakers are Klipsch La Scala IIIs which, in a larger room really need the extra "punch" a good sub can offer. Will send out my thanks in advance. I know this topic has been covered over and over again.
oldrider

Showing 3 responses by almarg

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almarg
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The previous owner had an additional set of RCA connectors installed for running some sort of sub within his system. I've come to find out that these 2 connectors won't work with my JL Sub ....
Can you provide further details on why this is so? I would expect that if the amplifier was modified to provide line-level outputs on RCA connectors for the previous owner's sub, those outputs should work with pretty much any other sub that provides line-level inputs.

Also, as a point of information, there is probably an additional reason why using the tape jacks would not work, besides the one Spinaker correctly cited. On the 801A version of the amp, at least, the pair of tape jacks that is provided are inputs, not outputs.

Regarding speaker-level to line-level converters, all of those I have ever seen are for lo-fi applications, such as in automobiles, and would not do justice to your JL sub. Also, many of them are not rated to be able to handle the voltages your amp may put out on its speaker connectors, without being damaged. It is possible to rig up a converter yourself, using resistors to divide down the signal level, but you may not be looking to undertake a do-it-yourself project.

So I would focus on what the problem is with the connections the previous owner added. Not sure what else to suggest.

Regards,
-- Al
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almarg
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How on Earth do other people wire a sub like this into a 2-channel system?
Since the sub has only line-level inputs, and not speaker-level inputs, it would normally be used either in systems having a separate preamp and power amp, or having an integrated amp that has jacks providing the outputs of its preamp section.
Was told by Galen Carol in Texas (after having paid a few hundred to ship down and then back to Alaska) that the connections were "passive" and wouldn't have enough voltage to drive the Fathom i have.
What are the symptoms you are perceiving? Inadequate volume from the sub?

Using a passive output may or may not provide adequate volume depending on the input impedance and the voltage sensitivity of the sub (both of which appear to be unspecified), and the output impedance of the passive output (which I presume is unknown).

If that is in fact the problem, a solution would be to connect those passive outputs to the inputs of a simple, no frills (but decent quality) preamplifier, and connect the preamp's outputs to the sub. The preamp would present a high input impedance to the passive outputs of your amp, so it would be easy to drive, while driving the sub from a low output impedance and providing adjustable voltage gain.

Hope that helps. Regards,
-- Al
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almarg
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Johnny, as I indicated in my initial post in this thread I'd be skeptical that a cheap transformer oriented towards car audio, and perhaps even Carver's Z1 Coupler, would do justice to the OP's system, and to a JL sub in particular. As I'm sure you realize, all transformers are not created equal, and that is probably especially true in the deep bass region.

Also, are you sure that "any powered subwoofer that has speaker inputs has a similar transformer inside to pass the signal to the internal sub amp"? I have no particular knowledge of how that is generally done, but I would expect that in many or most cases it is done with resistors configured into a voltage divider circuit, not with transformers, resistors being a much less expensive approach compared to a quality transformer.

Regards,
-- Al
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