Pr11A powered on without speakers connected?

[pstrisik]

I'm trying to set up a configuration where I have a two channel tube system integrated with my home theater system. Without getting into all of the complexity, basically I'm having a Pr17LS pre into a Pr11A amp for two channel. I have an Onkyo pre/pro into Class D solid state amps. I want to run with a single set of main L/R speakers. I have a switch to accomplish this. Problem is, I would like the tubes to stay on at times when I will be listening to music after our movie so they will be warmed up and ready. When watching the movie, the switch would disconnect the speakers from the 11A.

Is this a risky proposition? The maker of the Class D amps says no problem, but I think I've heard that it can be a problem with tube amps.

I'll call C-J tomorrow but thanks for any insights while waiting. ........ Peter

NB: this will be the first call since Ed left. http://fc06.deviantart.net/fs71/f/2011/146/c/8/_saddestthingintheworld_by_sml_e-d232ut1.gif

[rthomeint]

You don't want to leave the amp on with no load connected to the speaker terminals. I pretty sure to amp can be damaged. If the amp is running and you go to attach speaker cables you short the amp by accidentally touching positive and negative legs on the amp. Then it will have to go back to CJ for repair. I know this from personal experience.

FTW I call CJ last week and was told by the receptionist to send an email, since Ed left I don't think there is anyone there to field tech calls anymore.

[ronenash]

Its a bad idea to leave a tube amp running with no load for a long period of time. Its OK for a few minutes but more than that can result in oscillations damaging the output transformers.

[pstrisik]

Thanks guys. I'll email CJ, but it sounds like I can't go this way. Bummer. The only way I can see to do it at this point, is to have separate speakers - kind of a drag. The other alternative is just to go ahead and use the 11A for both home theater and 2-channel and up my tube budget!

....Peter

[rthomeint]

Thanks guys. I'll email CJ, but it sounds like I can't go this way. Bummer. The only way I can see to do it at this point, is to have separate speakers - kind of a drag. The other alternative is just to go ahead and use the 11A for both home theater and 2-channel and up my tube budget!

....Peter

I have done this in the past with the 11A for front Left and right speakers and the a MV52 for the center and a son of Ampzilla on the rears. I got really good surround sound out of this setup.

[pstrisik]

I have done this in the past with the 11A for front Left and right speakers and the a MV52 for the center and a son of Ampzilla on the rears. I got really good surround sound out of this setup.

No question about the sound quality Rob. I just want the amp to last a very long time. It may be the most practical solution though.

......Peter

[ronenash]

Thanks guys. I'll email CJ, but it sounds like I can't go this way. Bummer. The only way I can see to do it at this point, is to have separate speakers - kind of a drag. The other alternative is just to go ahead and use the 11A for both home theater and 2-channel and up my tube budget!

....Peter

This will also give you the best sound from the L & R speakers. I would not be too concerned with tube life as the Pr11 uses only 4 output tubes and its not known to hard on the tubes.

[pstrisik]

This will also give you the best sound from the L & R speakers. I would not be too concerned with tube life as the Pr11 uses only 4 output tubes and its not known to hard on the tubes.

Any estimate of tube life on the 11A? CJ FAQ on their site says:

Q. How long do tubes last?
A. That varies depending on the type of tube, the number of hours of use and the type of use they have had. Typically tubes should last, on average, about 1500 hours before gradual degradation of performance becomes noticeable. This translates into two to three years if the unit is turned off when not in use. Usually tubes will continue to be functional for a long while after this, but sound quality will be reduced and noise levels will increase. In power amplifiers, the input tubes are most critical for sonic performance. If output tubes are not causing problems, they can be replaced every other time.

1500 is pretty generic - across all amps and tube types. And 1500 hours is only about a year for me if I use it for theater and music. I'm using KT120 for output tubes, btw.

......Peter

[pstrisik]

Just got this reply from CJ service dept:

Peter,

It is generally not a good idea to run a tube amplifier without a load. Unless your switching arrangement can switch in load resistors (any value between 4 and 100 Ohms should be suitable) when the amp is disconnected from the speakers, I'd leave the amp switched off until you connect the speakers. You can turn the preamp on at any time to let it warm up.

regards,
customer service

I guess my other option is simply to not have warm up time for the amp when watching movies.