How to go from RCA to XLR?

One channel of the amp will be the positive input the other the negative of the XLR. This will bridge the amp but it will be balanced bridged operation. This is what the Pallidiums and MBLs are I believe. It is a pretty common. One of the outputs to the speakers will be the positve and the other positive output will be the negative or ground. Just like with a bridged stereo amp.

That sounds ok to me at the output side. The speaker would be connected between the two positive output terminals of the amp (I think, although I'm not certain offhand, that you would want to use the 16 ohm taps if you have 8 ohm speakers), and the two negative output terminals of the amp would be left unconnected (they are tied together and to signal ground internally).

On the input side, I think you are saying that you would take your xlr source (transformer or preamp), and construct a cable that ran xlr pin 2 to the center pin of an rca plug, and xlr pin 1 to the ground of that rca plug, and ran xlr pin 3 to the center pin of another rca plug and xlr pin 1 to the ground of that second rca plug. The two rca plugs would then plug into the amp's two rca inputs. Correct?

Or are you saying that you would replace the rca inputs on the amp with an xlr connector that you would install, with pin 1 wired to amp ground, pin 2 to the single-ended signal path of one channel (wherever the center pin of the rca had been wired to), and pin 3 to the single-ended signal path of the other channel?

I think that everything would function either way, but I'm not sure that you would gain all that much in terms of noise rejection, especially if you don't replace the rca input connectors. Balanced inputs reject noise that is present equally on both polarities, but with the two polarities being physically branched off I'm not sure that noise pickup would be really equal. You will gain a lot of power, though.

Regards,
-- Al

This is from the Citation II manual and Jim Mcshane's site.

((Connecting Citation Amps In Mono (Bridged) Mode
Here's the how-to, right from the original H-K manual:

In order to operate the Citation II as a 120 watt monophonic amplifier it is necessary to fulfill two requirements:

1. The speaker output terminals must be strapped together. Tie the two ground terminals in parallel and then tie either the
two 8 or 16 ohm terminals in parallel depending on the nominal impedance of your speaker. For example, if you are using
an 8 ohm speaker, tie the two 16 ohm terminals together and attach the speaker between either 16 ohm terminal and
ground. If you are using a 16 ohm speaker it is permissible to connect it as described for an 8 ohm speaker, as a
mismatch of as high as 50% will not affect the tone quality.

2. The amplifier input terminals must be tied together if no preamplifier is to be used and the signal is being fed directly
by a tuner. If a monophonic preamplifier is used it is also necessary to tie the inputs together. This can be accomplished in
any of several ways. One method would be to use two patch cords with RCA type phono plugs on one end. The other
end of these patch cords would be tied together in parallel and soldered to another RCA type phono plug. Connect the
two individual RCA plugs to the input receptacles of the amplifier and the other end (which is paralleled) to the output of
your tuner. A more satisfactory method is to purchase a LAB-TRONICS patching plug, Part #A-7 54 to parallel the
inputs of the amplifier. This device would eliminate the need of soldering and would insure perfect connections.

3. If a stereo preamplifier is used input strapping is not required. Merely connect the two outputs of your preamplifier to
the corresponding inputs of the Citation II and connect the speakers as previously discussed.))

Yes, I would install an XLR for the inputs. I think noise rejection would be excellent. This should be the same as any other differentialy balanced amp which is what I should have. I also think the amp should have more than double the power this way. If anyone elso wants to weigh in you are welcome. Sorry to hijack the post though.

What the manual describes is not differential and is not balanced. It just converts the amplifier to mono by paralleling up the channels, resulting in a single-ended amp with twice the power.

-- Al

I know Al, if it were that easy I wouldn't be asking. The amp is 50 years old. I don't suppose they had much balanced audio equipment then. I hope to get more power and noise rejection by doing it in a balanced configuration.