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subwoofer connection to unfriendly amp

I have a REL B-3 sub. The REL cable is terminated with banana connectors on the amplifier end which works fine for connecting to my VAC PA100 output terminals. I would also like to be able to connect the sub to my VAC Phi 110. I like to switch between the two different amplifiers and also would like to be able to utilize the sub with either amp without a total rewire each time.

The Phi 110 has ouput terminals whereby you tighten both +/- leads at the same time via a large knurled knob that is secured to a threaded post between the terminals and presses inward against a plastic bridge. There is no provision for a banana connector.

Since the REL cable only uses three terminals, even if I switched to spade connectors, I would not be able to tighten the speaker wire on one channel due to one terminal possessing two wires and the other only one wire. Plus it is difficult just as it is, to hold the speaker cables in place and tighten the knurled knob.

I was thinking of making an adapter box with speaker terminals that would accept the banana terminals mounted into a small box. Then run some decent wires out and use eyelet terminals on the amplifier posts to prevent them falling off. I would also add one dummy wire so the the amplifier terminal will tighten evenly.

So the questions are: Where is the best place to find the parts to do this? Is there a better way to accomplish the subwoofer changover between the two amplifiers that I have not considered?
rhljazz
xti16
1,525 posts
 
Use high quality jumpers from the amp to the selector switch.
I was thinking of making an adapter box with speaker terminals that would accept the banana terminals mounted into a small box. Then run some decent wires out and use eyelet terminals on the amplifier posts to prevent them falling off. I would also add one dummy wire so the the amplifier terminal will tighten evenly.
The speaker cables must run unimpeded from the amp to the speakers. I don't want any degradation in the signal delivered to the main speakers
Sounds like the same thing except some selector switches may have better contacts and internal wiring for the actual speaker selection.
ghostrider45
449 posts
 
I'm not sure I understand your proposed hook up without a diagram, but it sounds like you're planning to hook the REL to both amps simultaneously without a switch.

This will effectively route the output of the active amp to to the output of the inactive one. The results won't be pretty.

You need a switch.
rhljazz OP
1,255 posts
 
07-16-08: Ghostrider45
I'm not sure I understand your proposed hook up without a diagram, but it sounds like you're planning to hook the REL to both amps simultaneously without a switch.

This will effectively route the output of the active amp to to the output of the inactive one. The results won't be pretty.

You need a switch.

I only wish to connect to one amp at a time. The REL cable is currently terminated with banana connectors which the PA100 amp accepts and the Phi 110 amp does not. I am seeking an interface that would allow selective connection to either amp without reterminating the REL cable every single time I want to switch amps. I do not want the speaker cables hooked to a switchbox. Extra wires and connections in the signal to the subwoofer doesn't concern me as much.
ghostrider45
449 posts
 
I'm picturing a homebrew box with the banana jacks as you mentioned and a switch to select the desired amp. The output would be to two sets of eylet terminated wirers, one for each amp. Is this correct?

The good news is that your switchbox won't handle any significant power. The REL presents a high impedance to the speakers and no significant current flows to the sub. It merely senses voltage at the speaker terminals.

As long as both amps have common ac ground you can get away with switching just the right and left channel hot leads (the third is ground), so a DPDT switch will do.

To be honest, I don't know where to look for an audiophile grade version of such a switch. You can look online at places like partsexpress.com.

As others above have mentioned, you can use a simple speaker switch for this. Hook the REL to the "amp" terminals and the Two power amps to the "speaker" terminals (i.e., backwards). The switch won't handle any of the power going to your speakers.

I don't think you have this problem with your amps, but beware that the REL only works on amps that share a common ground between channels. Some amps use floating outputs, and the REL hookup will cause problems.

Good luck!
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