Thanks to all for your comments. The pot idea to determine resistor ratios
required to keep volume control consistent with that for speakers sounds
good. I will also use larger values than I originally planned.

Thanks again,
John

"CJT" wrote in message
...
normanstrong wrote:

"John Richards" wrote in message
news
I would like to drive Sennheiser HD 580 headphone from the speaker

terminals

of a 120 watt amp. The headphones have a nominal impedance of 300

ohms,

power handling of .2 watts and sensitivity is 97dB (at 1 mW?). My

intention

is to wire resistors in series across the outputs of the amp to

limit the

voltage to the headphones thereby assuring that the headphones will

not be

over driven and the volume control will operate in a reasonable

range.

Get a 10K pot,

10K seems pretty high; maybe more like 250 -- and wirewound.

preferably with an audio taper, and put it across the
output of the amp. Connect one of the phones from the tap to common.
Set the volume of the amp so that it sounds normally loud when
connected to your speakers. Now disconnect the speakers and set the
pot so that the phones have about the same loudness. Measure the
resistance of the pot from tap to common and from tap to the amplifier
input. Buy a pair of resistors of about these values, a pair for each
phone and connect them permanently.

Another, even better solution would be to copy the divider on a
commercial receiver.

Norm Strong




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