Please help me understand this transformer spec

[Blasty]

I am toying with the idea of building a new headphone amplifier, and ran across this transformer which looks like it would be great to use in a parafeed design. Upon further research, it was apparently designed just for this purpose.

http://www.edcorusa.com/pcw10k-7k_300-32

Please look at the specifications. I do not understand how this transformer is rated for 1/2W yet has a maximum voltage input of 15Vrms.

(15^2)/10k = 22.5mW

To reach the rated power, I would think the primary voltage swing would have to be closer to 70Vrms. I can't imagine the wire in the primary winding having any problems passing 7mA, either.

(70^2)/10k = 490mW

Although this amount of power is excessive for most headphones, I will certainly want more than 22.5mW.

Am I missing something silly here?

 

[kward]

Something doesn't seem right. If we take for truth the wattage rating, then the 10K primary is a "70V" line input, which seems appropriate if it's a line matching transformer.

At 1/2 Watt, the secondary would swing 12.2V on the 300 ohm winding. So 15V max seems like an appropriate statement. It's possible the typo is that its 15V max on the secondary rather than on the primary.

 

[Tom Bavis]

Specs are incomplete - I'd expect DC winding resistance, primary DC current to be specified - doesn't say if it's gapped, so parafeed may be only choice. The frequency response is specified at 0 dBu, less than a milliwatt, but the important power limit of low-frequency saturation isn't mentioned. It's possible that it will saturate at 22 mW at 20 Hz but can handle 1/2 W at higher frequencies. But can't tell from the limited information given.

 

[Blasty]

Thanks for your replies.

I do know that it is not gapped. Putting the part number into a search engine brings up an artitcle that mentions such. This also turned up some references to the Beezar "Torpedo" headphone amplifier, which it appears this transformer was designed for. This is another reason why the specs seemed odd. I didn't find complete specs for the amplifier or a schematic with values.

At their low price, I may end up ordering a pair to do some tests with.