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Question About Headphones with HK A50K

C

ChadHahn

Active Member
I have a Harman Kardon A50K amp. On the back the speaker inputs have a wire that you can clamp down to change the impedance for the speakers. In the instructions it states that, "The jack will accept headphones with the same impedance ratings available for speakers. The impedance selector wires should be connected to the 4, 8, or 16 ohm terminals in accordance with impedance rating of your headphones."

The headphones I have are 32 ohm. The speakers I have hooked up are 4 ohm. Will I hurt the amp playing my headphones through the amp when it is set to use the 4 ohm speakers. Since the highest impedance is 16 ohm can I even use the headphones? It says that the 16 ohm terminal is for speakers from 12 to 20 ohms.

Thanks,

Chad
 
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Well, MAYBE you could hurt your amp, but your ears would be bleeding LONG before you reach that volume level... headphones need a tiny fraction of the power that speakers do.. Generally, a series resistor or resistor voltage divider is used to reduce the speaker output to an appropriate level for the headphone jack. Otherwise you'd be using only the first few degrees of the volume control, and a tiny amount of noise or hum would be unbearable.

In the A-500 (I assume the A50K is similar), the voltage divider consists of a 330 Ohm resistor and the parallel combination of the headphones and your speakers (if you have any connected...) 330 Ohms is a pretty big mismatch whether it's set for 4, 8, or 16, but that doesn't matter since you're delivering milliwatts at most - matching is needed for maximum power delivery, which is not wanted here. The 4 Ohm tap will be fine.

A possible problem though - the frequency response delivered to your headphones will depend on the frequency vs. impedance curve of your speakers. I would have chosen to use a separate voltage divider and speaker on/off switch to avoid this affect.
 
Thanks for the reply. I was worried since I set the amp up to mostly use with headphones and didn't want to fry it.

Chad
 
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