Sony TAE 1000 ESD - mute speakers for headphones?

Dumb question ...

I can't figure out how to listen to the headphone jack and mute the speakers. When I press the mute button, it mutes both the speakers and the headphone jack.

Any ideas?

p.s. I lost the manual years ago
From the manual: "Headphones Jack: Accepts the stereo phono plug of headphones. The jack outputs the sound of front speakers only. To listen to the program source only with the headphones, turn off the power amplifiers as the unit does not turn off the line output when the headphone plug is inserted."

Hopefully your amps have volume controls, a mute switch or a standby switch.
Thanks for your help Alexander. I'm a bit confused, though. The manual says to turn off the amplifier. OK, I guess there will be enough power going to the cans without the amp.

But then you said "hopefully your amps have volume controls, etc" ....

I don't think my amp (Adcom) has mute switch or standby switch, and I know it doesn't have volume control. Are you just saying this because it would be a little easier to NOT have to turn off the amp?

Thanks again!
Some members find it advantageous to leave their amps on all the time. Seems your only option is to turn yours off to use the headphones. I'm not familiar with the Adcom to know if it has a mute or soft start circuit in it. Obviously start at low preamp volumes and slowly increase and listen for speaker volume to hear if any signal is passing thru the (turned off) amp.

I just noticed that my Adcom has a switch on the front to cancel the speakers! I'm good to go.
I need a manual for my7 sonyTAE1000ESD a copy would be greatlly apprecated