24.18.227.0
In Reply to: RE: Out board output transfomers..... posted by Bmotorcycle2003@yahoo.com on February 15, 2009 at 05:52:46
I agree with the other posters, the two considerations are high voltage safety and excess capacitance.
You will be running something around 400vDC plus maybe 200vAC (totalling nearly 700 volts peak) on one wire of the cable. This is an exposed cable, where moving furniture or stepping on it accidentally or a dog chewing on it can expose the wire, so a grounded shield should be used in addition to the two wires (and ground the transformer frame and core unless they are inside a grounded shield box and isolated from that box). Cable rated for such a high voltage is not common; you may want to look at what ham radio operators use for transmitter outputs for example. You may want to look into a safety rating, not just an electrical rating. Remember, safety ratings (like UL and electrical codes) are mostly based on preventing specific things that have already killed people.
Commonly available coax has a natural impedance of 50 or 70 ohms. Above that impedance, the cable is predominantly capacitive. Coax runs 50pF to 100pF per meter, so you are looking at maybe 300pF. That is on the order of the capacitance of the transformer winding so it will have a significant effect on the transformer's high frequency response, probably changing both the frequency and the Q of the main HF resonance. For a biamped midrange that may not be a big concern.
Just some thoughts, hope that helps.
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