Amps that switch on when receiving an audio signal


I see that there are power amps from Cambridge Audio and Parasound that switch out of standby and into operating mode when they receive an audio signal. This seems to me a pretty cool feature -- cool in more ways than one, of course. (Energy saving, etc.) Are there other amps that do this? Are there many? Is this becoming something of a commonplace and I'm just now noticing it?

Thanks.

-- Howard
hodu
I already have the ridiculous hassle of having to hit the "warm up" tube power amp switch after the power conditioner start sequence. That's at least 10 seconds a day that I'll never get back...
My REL is important dammit...and it has that feature working perfectly for years, although if it wasn't I'd be unhappy...because it's so important...
"Not really important no great amp have this."

Important to who?

Its a nice feature if one cares. Some do apparently. I would not mind having it if all else is in line as well.
The (low-end) Sony subwoofer I use for home theater does this and it's a real bother (relay is very noisy).
Frequently clicks-off when no LF present in program.

Another function I've seen is auto off-on (Pretty sure my ARC VT-100 had this). A control cable is used to turn amp on-off depending on the state of the pre-amp.
My Sony does, and also turns itself off with no signal after 15 minutes. Utterly love both features. I hit pause on the Sony server when music is playing, leave the house, and both units auto shut off.
My Sunfire 300 only uses 20...25w stand-by so no need to switch on-off. It stays on 24/7 and always ready to blast music.
I have an old Harman Kardon amp from the mid 90s that has that option.
As for subs, most powered subs offer this option.

A while back I bought an amp on ebay (can't remember the brand) that was listed as "dead" for parts only. When it arrived I noticed it had an auto on switch. I turned the switch off and the amp worked great. After some research I adjusted the auto on trigger and that worked great also.