(Posted this in the subs forum but no one had anything to say - hoping another 2105 owner has an insight) I've changed amps from a Yamaha A5 to a Denon 2105 because there seemed to be problems with the sub output - i.e. there wasn't one most of the time. The sub wouldn't wake from standby by itself and would go to sleep after 15 minutes as if there were little/no signal going to it even at quite high volumes. As I'm using a sat/sub combination there should always be some signal. Running the sub from a line level tape out - it seemed to stay 'awake' so I figured the amp was bad and the sub was fine. (I knackered the A5 plugging it into the sub with the power on fried the 'mute transistors' according to Yamaha on email - resulting in a nasty thud and nothing more from the sub output. Time for a new amp.) Unfortunately I'm still having problems with the new Denon. I need to turn the Denon master volume up to around 0dB to get the sub to wake, then turn it down and a few minutes later it will go to sleep as though there were little or no bass input - even though it is making a noticeable output. I've tried increasing the sub output to +12 in the amp settings and lowering all the other levels to bring up the master level on the amp - still the same effect. The sub seems to work normally when using a 5.1 source. I'm beginning to think the sub has a problem with the auto standby function but unfortunately there is no permanent 'on' switch. I also took it apart and the electronics are sealed so there's no way to by pass the auto off function. I would replace it but I'm worried that it's actually the amp has a very low output level and I could end up shelling out for a new sub and wind up with the same problem. Anyone got any suggestions I could try to keep the sub awake by a change to the settings on the amp? Had a similar problem with a 2105? Thanks for looking - any help welcome!