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Is It Safe To Connect Speakers To Two Amps??

i've got a combined HT and 2-Channel rig whereby my mains and subs function in both. i'm currently using the traditional connection scheme whereby the HT processor sends signals to the mains via the pre outs to my preamp (in bypass mode) then on to my main power amps, then on to the speakers.

if i wanted to bypass my preamp and main power amps althogther (it's a shame to burn tube hours on movies), is it safe to simply connect my main speakers to the HT processor via speaker level connections if they are also connected to my main power amps concurrently? only one amp - HT processor OR main amps - would be running at a time.

any inputs would be greatly appreciated.
128x128srosenberg

Showing 6 responses by hifihvn

hifihvn
943 posts
 
No, it's way to risky. I don't know how the Niles is made, so I wouldn't risk it. A lot of switches are made with solid state only in mind. And you did mention tubes. First off, with any switch, the plus and minus both should be isolated, through the whole switching device.

With tube amps involved, there should be a load resistor on a tube amp when the switch is in the other amps position. That way there would be a lot less risk. Even if your careful enough to not make a mistake. If you switch off the tube amp to turn on the SS amp for the TV, the switch needs to have a load(load resistor) on the tube amp. The reason would be the tube amp power supply would hold a lot of voltage stored in it when turned off, and any little noise could cause the output transformers to short out. This noise could happen during the switching, or a tube or other part while cooling down. It needs a dummy load, or speaker load on it all the time, just in case there is that voltage stored in it. It is quite common for tube amps to hold that reserve voltage, for unknown lengths of time. To many unknowns make this a risk. That relay system might have zero protection for this.
hifihvn
943 posts
 
The relay system I'm referring to would be in the switch. I should have said the protection system used in the switch, might offer zero protection for the amp, in this case.
hifihvn
943 posts
 
Tklp, what tube amp are you using?

Niles themselves have concerns about keeping a load on the tube amp at all times, in this speaker switch(link below). They recommend an extra resistor on the tube amp at all times on some products. I don't know if the 150ohm,5 watt resistor would be safe for all amps. I would not try it, unless the company that built the amp says ok. The other switches do not even mention tube amps, and whether it would be safe. Maybe the manufacturer of your amp could recommend what to do. This PDF link is for a speaker switch, that expresses the load at all times. Pages 4-7. [http://www.nilesaudio.com/images/PDF/SS_manual.pdf]
hifihvn
943 posts
 
One other possibility might be to shut your tube amp down (its own power switch) while the music is still playing. I don't know if this this would be safe for your tube amp. If not, let the tube amp at least cool down enough so the tubes can't amplify anymore (few minutes?). Then switch it over with a good switch that doesn't use resistors while playing. This might be one to ask your amp company to see if it's safe to do. Others please chime in, if this is not a good idea. I'm not sure.
hifihvn
943 posts
 
Then switch it over with a good switch that doesn't use resistors while playing.
Let me clarify. I don't mean change the switch over with music playing, just no unneeded resistors a switch might put in the signal path. Definitely the amps should be off to change over. Sorry.
hifihvn
943 posts
 
Almarg, thanks for clarifying.
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