noisy mcintosh 6100 phono channel

hi any help is appreciated, i have a mcintosh 6100 and i have just noticed that when the phono stage is selected, but no record is playing or even the record player is unplug, that there is a wind like noise that increases as the volume is turned up. i thought it might be the ground so i messed
around with the wires in the back and ended up just unplugging the record player and testing other channels, it seems to be the phono channel only. any ideas? thanks a bunch
Could be a tube going bad in the phono section ..( if it a tube unit )...........