You can get the advantages of balanced input (i.e. good common-mode noise rejection) from an unbalanced source if the component in question uses input transformers which can offer excellent common-mode noise rejection even when fed from unbalanced sources. However components using input transformers are quite rare. se |
The following reference is a bit technical, but well worth reading: http://www.jensen-transformers.com/an/an003.pdf There is no general answer as to which is better, because many variables are involved, encompassing the equipment design, the noise environment, the ac power distribution scheme, the parameters of the specific cables being used, etc. Note in Figure 2.1, though, that a properly done rca-to-xlr adapter arrangement WILL provide some degree of common mode noise rejection, although not nearly as much as adapting via a high quality transformer. But if the amp is not "fully balanced," meaning that its internal signal path is unbalanced, that benefit may or may not be outweighed by the sonic effects of the extra stage that would be present at its balanced inputs to convert them to unbalanced internally. Regards, -- Al |
Addendum to my previous post: I should emphasize that in Figure 2.1 of the reference I linked to, it should be noted that the adapter arrangement is NOT simply an xlr-to-rca adapter at the destination component's input, fed via an rca-to-rca cable. To achieve the common mode noise rejection he describes, shielded twisted pair cable needs to be used, with the lo/cold/inverted signal line grounded only at the source end. That configuration prevents signal return currents from flowing through the cable shield in common with inter-chassis noise and hum currents, which is what would happen with an rca-to-rca cable. The twisted pair construction also helps to assure that noise pickup is common mode (i.e., that it is as similar as possible on the "hi" and "lo" signal leads, so that the differential receiver stage can reject it). Regards, -- Al |
