Hello I am a newbie in all this stuff, so I would appreciate any help on this. I have come to posses an old amplifier, a Victor JA-S11 Stereo Integrated Amplifier, it is working very well and excellent sound quality. It has Headphone output jack. Currently I don't have any speakers to use it, and I thought about using an old headphone, it is a LLoyd's Stereo Headphones MODEL Y691. My question is, can I use this headphone with this amplifier without causing damage to the amplifier or the headphones? Also, how can I determine the headphones impedance? I have tried to find this information on the web, but since these are very old equipment I couldn't find anything about neither of these two. Thanks a lot!