Mystery loss of power.

It may have been the thermal cut-out protection kicking in.  Was the NAP250 case hot?

Thanks Richard. Didn't check for that,  but I'll pass it on and consider re-siting when it gets back to me.

It was on the bottom shelf of an Isoblue stack. Is this setup known to blow the NAP250?

If it exceeds 70 degrees C then the thermal trip will go.  Was the room quite warm? What are the speakers and the speaker cable?  Length? 

My NAP 250 regularly cut out due to overheating at volume - cured it by buying 135s. My previous NAP 90 never did it strangely enough, and neither have any of my Unitis. It always happened when I was really having a good rock out or having a party - pathetic having to explain how your mega expensive amp won't go loud for more than a short time

If the new series 250 is anything like the olive 250 it needs all the cooling it can get. 

Half way up on a 282 (i.e. around 12 o'clock on the dial) can be quite high, especially if the source is CD/Tuner (i.e. higher input level than many a vinyl set-up) in to say 'demanding' 4-ohm speakers e.g. some Dynaudios. My 52/Olive 250 on Fraim (+ NACA5 ~6m runs) shut down several times when driving my Dyn 1.8 Mk II's, even though on paper they were stated to be a stable 4-ohm load (??). 

IIRC, there was some chatter on here about the suggested max volume for CD being around 12 o'clock on the dial, as the amp would be working near capacity due to the higher input signal, as relative to many vinyl inputs.

One thing to check is if the speaker cable terminals are properly seated at both ends too. 

Streamer only. Epic 2x4m. Logo light went off  so total shutdown...

I normally run it at about ot ten o'clock. I'll just have to stop playing along to tunes with my drums.

Interestingly, the NAP200 never gives me a problem when I do this.

FWIW - A few weeks ago I came home on Friday evening after a day that wound me up, put on the music and started turning up the volume. A short time later the music stopped and while trying to figure out what was going on the music started playing again, then shortly thereafter stopped again. This time I physically touched the SN2 and it was very warm to the touch. Called the dealer and the first statement he made was "you must be cranking up the volume" which I acknowledged. He then mentioned that the SN2 had a auto shut down switch when it reached a certain temperature so that the box would not be damaged. I reduced the volume got the music started and no issue after that.

NDX > SN2 > NAC A5 (14 feet/4.27 M) > Ovator S-400

Mike1951 posted:

Streamer only. Epic 2x4m. Logo light went off  so total shutdown...

I normally run it at about ot ten o'clock. I'll just have to stop playing along to tunes with my drums.

Interestingly, the NAP200 never gives me a problem when I do this.

The NAP250 needs good ventilation as it only has the casework to dissipate heat (no fan like on the NAP135, 300, and 500).  When working hard it will be putting more heat through the case than something like a NAP200, mainly because it's special - it's a regulated amplifier, so a bit like 2 amplifiers in one, and as it's regulated it can't let things a slide a bit when the going gets tougher like other (unregulated) amplifiers.

In the old days of running Isobariks at high listening levels with NAP250s in hot climates, owners were known to place the 250s on their side edge to maximise cooling, and even to have room fans blowing air on them in order to prevent thermal shut-down.

Ah-ha! I feel a re-stacking coming on...

volume ast 12 o clock. 

blimey that is seriously loud.

it's a domestic amplifier - not a PA.

I don't know how some of of you manage to shut down your amps, it is something I have never managed to do, but then I don't want to damage my ears.

[@mention:70553749506420292] - Hat off to you, sir.  I drive my SN2 reasonably hard, permanently above 9:30, normally around 10 and sometimes around the 11 o'clock mark, which with my speakers is pretty loud (recording dependent), and I've never known it be anything more than slightly above room temperature.  You must have been really going for it that day. ;-)  I'd love to know what was playing at the time to aid in the unwinding. 

SongStream posted:

[@mention:70553749506420292] - Hat off to you, sir.  I drive my SN2 reasonably hard, permanently above 9:30, normally around 10 and sometimes around the 11 o'clock mark, which with my speakers is pretty loud (recording dependent), and I've never known it be anything more than slightly above room temperature.  You must have been really going for it that day. ;-)  I'd love to know what was playing at the time to aid in the unwinding. 

Going back and tracing my steps.......   I started out that evening with a Sting album 'Nothing Like the Sun' and had cranked the volume above my usual 9 to 10 O'Clock position and made it through that album. I then put on a Fink album 'Perfect Darkness' and cranked the volume louder I believe around 12 Noon and was somewhere into the second track and then the pause......

(disclaimer: I know the albums because I looked them up on the forum for the evening in question. The exact position of the volume control is where I can not truly say that the information is completely accurate. Controlling the volume remotely on the iPad using the + / - tabs does not leave the visual memory that walking over to the dial and manually adjusting the volume. ......and I'll also use the age thing being a senior citizen .....)

When I spoke to the dealer he mentioned that the Ovators can require the amp to work hard at high volumes which caused the amp to momentarily shut-down to protect itself.