Best way to wire up a sub


I have a new pre-amp with only XLR connectors and want to use my older Velodyne sub which has RCA input's only.
My question is can I just use an XLR>2 RCA's cable (using a Y Connector)?

My older pre-amp just had an RCA so I used a Y connector and then into the sub with no issues so I assume the XLR connector would work the same way etc.

If I understand correctly the sub provides separate left and right channel inputs on RCA connectors, as does the power amp, and you want to connect the XLR output of the preamp (for each channel) to both of those RCA inputs.

Yes, you can probably do that with good results, but there are some potential issues to be aware of.

First, most XLR-to-RCA adapters short XLR pin 3 (which conducts the inverted signal in the balanced signal pair on most equipment sold in the USA; the non-inverted signal in some other countries), to ground (pin 1). That would be no problem with a lot of equipment, but the output stages of some components will not be happy having an output signal shorted to ground. My understanding is that Cardas adapters do not do that.

Similarly, if you use an XLR-to-RCA cable instead of an adapter you would want to specify to the supplier that the unused signal pin on the XLR connector should be left unconnected. (A possible exception, for both an adapter and an adapter cable, being if the preamp has transformer coupled outputs; in that situation it could conceivably be necessary to short pins 1 and 3).

Second, as with many subs the input impedance of the line-level inputs of the Velodyne models tends to be low, I believe typically something like 15K, and perhaps less. So if your new preamp has a relatively high output impedance, which is particularly likely if it is a tube preamp, the combination of that input impedance and the input impedance of the power amp may be too low for the preamp to drive without sonics being compromised, at least slightly. If you'd like to have that calculated specifically, let us know the make and model of all three components, and the impedances if you know them.

Finally, if the preamp has relatively high output impedance, and if either or both of the cable lengths are long, you would want to make a point of choosing cables having low capacitance per unit length. Otherwise the interaction of the TOTAL capacitance of the cables to BOTH destinations (sub and power amp), if high, and the output impedance of the preamp, if high, may perceptibly roll off the upper treble content of the signals received by the power amp driving the main speakers.

-- Al
I have an older Velodyne sub with RCA inputs only. I find it much too boomy for 2 channel but fine for HT. I have it going through a A/V processor using the sub out RCA. I have JL subs coming out of my preamp connected with XLR cables. The JL's are a significant improvement over my older Velodyne but at a cost.

Thank you very much for your detailed reply. You have answered my question in spades.
Towman, as you sort through some of Al's excellent points, it may turn out that you need an impedance buffer that provides the multi-functionality that my buffer has.

Rather than write a long response at this point, I'll let Al work with you on resolving your question. Just keep in mind that hooking up a sub to your preamp may present some of the issues that I had re (i) impedance (load) presented to the pre, (ii) summing channels, and (iii) matching the pre's XLR output to the sub's SE input.


I actually connected it up and it lasted about 3hrs. Now the sub has decided to die. It has served me well over the years...thank you Velodyne.
Anyway going to buy a DD+ 12 or 15 this week to rock my new media room that will be built very shortly.

Thanks for the replies.