330ohm resistors on headphone jack?

[dentaku]

I salvaged some parts from an old Akai audio/video receiver and the headphone jack has 330 ohm resistors on the left and right channel pins.
I don't think I've seen this before. What purpose do they serve?

[Audioguru]

They reduce the levels so the headphones are not so loud that your ears and head blow off!

[dentaku]

They reduce the levels so the headphones are not so loud that your ears and head blow off!

Well yes, but I usually haven't seen resistors attached directly like this to the headphone output.
The device has a volume control so adding a fixed 330 that way looked weird.

[basinstreetdesign]

They reduce the power delivered to the headphones so they sound just as loud as the speakers at the same volume control setting.  Most people like a certain volume control setting and want the same volume either way.

[Zero999]

The disadvantage with adding a resistor in series with the headphones is it results in a poor damping factor.

Another option is to use a potential divider with a lower output impedance than the headphones.

[wraper]

That receiver does not have dedicated headphone amp, therefore they use resistors to reduce the power from the main amp. If connected directly, even if volume could be decently controlled (it cannot, it will be like minimum level and a bit higher headphones already get overloaded and damaged), in the absence of sound at zero volume background noise would be just huge.

[Gyro]

Regarding the positioning of the resistors right on the Headphone jack PCB, I would think that they might have done it to minimise the possibility of high level signals accidentally being applied to the headphone outputs, particularly if there's a lot of hard-wiring in the receiver. I had a JVC receiver that had them in the same place.

[mzacharias]

Virtually every home stereo amp or receiver has these. Prevents damage to the amplifier channel with a mis-wired or damaged headphone plug or wire as well as level matching. I still see these resistors burned from time to time.