amp shutting down

[leftwinger57]

Hi guys, At a different site this guy was moaning that his Yamaha665 was shutting down at certain times during a program. I also own a 665 and was wondering why an amp of this power shut down. I put on a movie and during a particular loud and rumbling scene it did shut down.I called Yamaha and they had their pat answer down. When they told me it's common for the amp to do this I almost through the amp into the tv and phone hopeing to hit them. This is so unacceptable that all they could say was bring it to an a/d to have it looked at. After a year this shouldnever happen, and one other thing their vol scale goes from-65 to+16 what the **** is that about. Isn't1-10 good enough. I'm really pissed, which also led me to the 2-channel path. Tons more reliability. Any one else w/ this problem....EXCUSE THE CURSE.......LW

[wuzzzer]

What do you have connected to the amp as far as speakers and electronics?

Your Yamaha is rated at 90 watts x 7 speakers at a 1kHz test tone. A 1kHz signal is incredibly easy for a receiver to amplify. In real world numbers most amps that state their rated wattage using a 1kHz tone will in actuality be outputting half or less of their rated wattage with all channels driven full-range. More than likely your Yamaha is putting out around 40-50 watts per channel in any surround mode. It doesn't take too big of an explosion or deep bass to eat those watts up in a hurry.

In all actuality you should be glad your receiver is shutting down so that it doesn't damage itself or your speakers!

[StephenM]

In real world numbers most amps that state their rated wattage using a 1kHz tone will in actuality be outputting half or less of their rated wattage with all channels driven full-range.

Indeed.

While weight isn't a 100% indicator of receiver/amplifier quality, it can be a useful and interesting metric to look. Generally speaking good quality amplifiers that deliver gobs of power under a variety of loads weigh a lot.

As a simple comparison, that Yammy weighs in at a hair under 19 pounds. Harman Kardon's AVR-1600 is rated at 50W per channel, and weighs in at a hair under 28 pounds. Which do you think is more honest in their rating technique?

[jacksonbart]

pants on the ground

[Coytee]

pants Amps on the ground

[]

[Rich_Guy]

pants Amps on the ground

I prefer my amps on a rack. []

[Groomlakearea51]

I was looking at SWMBO's rack the other day. Shut the amp down, and dropped.... oh well... We'll stay away from the rest of that... or maybe not [6]

[Ski Bum]

Hi guys, At a different site this guy was moaning that his Yamaha665 was shutting down at certain times during a program. I also own a 665 and was wondering why an amp of this power shut down. I put on a movie and during a particular loud and rumbling scene it did shut down.I called Yamaha and they had their pat answer down. When they told me it's common for the amp to do this I almost through the amp into the tv and phone hopeing to hit them. This is so unacceptable that all they could say was bring it to an a/d to have it looked at. After a year this shouldnever happen, and one other thing their vol scale goes from-65 to+16 what the *** is that about. Isn't1-10 good enough. I'm really pissed, which also led me to the 2-channel path. Tons more reliability. Any one else w/ this problem....EXCUSE THE CURSE.......LW

Check to see where the impedance selector on your receiver is set.

In the Yamahas, the 'low' impedance position limits current from the supply rails, ostensibly to prevent overheating. Unfortunately, the demands that music and movies place on your receiver are quite different than those to determine UL thermal safety compliance. That's why you got the pat anser from the Yamaha rep. Pushing low impedance speakers with the selector in the 'high' position is against manufacturer recommendations, and may void the warranty.

Here's what the Yamaha rep won't tell you, but it's true: the Yamaha's that have these impedance switches (except for their very top of the line) deliver more power before clipping, regardless of actual speaker load, when in the high setting. Compared to the signals used for UL testing, music and movie soundtracks are a relative walk in the park, and its highly unlikely that you would damage the amp by using the high impedance setting, regardless of actual speaker impedance. Also, with full juice from the supply rails available, the amp achieves higher output before clipping. So in the low setting, not only will the amp shut down prematurely, it poses higher risk to your speakers due to clipping occuring at a lower output. Think of it as something Yamaha put in to protect the amplifier, not your speakers.

If you have your receiver on the 'low' setting, that may very well be the cause of the shutdown you experienced.

Here is an interesting article on the topic. Look at the chart on the second page. Your exact receiver is among those tested, and it showed a 60% reduction in power output when in the low impedance setting (driving a 4 ohm load, 'high' impedance setting gives 224 watts, while the 'low' setting only gives 63 watts). That's a big difference, almost 6db more headroom in the high setting before the amp runs out of steam.

http://www.audioholics.com/education/amplifier-technology/impedance-selector-switch-1