I have been thinking of getting a tube stereo amp. I currently have a 5 channel amp driving 2 sets plus one center. I would like to use the tube amp for music only (stereo)and also use my current mains for both music and in 5 channel mode. Is there a way to hook the mains up to 2 amps or must I always switch manually back and forth? I don't want to use the tube amp for 5 channel but it may be the only way. Any advice. Thanks

Don

Why not use the tube amp for 5 channel? It will undoubtedly sound better for movies too, which have stereo music predominately in the left and right mains.

I have considered that. Having never owned a tube amp before I guess I was worried about tube longevity. I am considering an integrated amp. Why can't I just hook up 2 sets of speaker wires - one form each amp to the speakers? When listening to music only the tube amp would be on and when watching movies the 5 channel amp would be on. Would this work or am I missing something (which is very possible).

Don

You are missing something. The amplifier, even when powered off, does not present an open circuit to another amplifier.

When powered on, one of the design goals is to try and minimize the output impedance of the amp. In simple terms, the output terminals look almost like a short circuit to anything connected to them. This is not good if that something is another amplifier and there happens to be a signal present at one or the other set of input terminals.

Swapping speaker leads is cumbersome at best. You might try constructing a custom switchbox, using a couple DPDT break before make switches of suitable amperage rating. (DPDT - Double Pole Double Throw)
You would want to switch both legs of each speaker circuit which is why the double pole spec. Break before make assures you that there is no way to parallel the outputs of the two amplifiers. Add a box and 4 sets of dual banana plug receptacles and you're pretty much there. Digi-Key, Allied Electronics, and Newark Electronics will have the necessary parts in their on-line catalogs.

Good Luck.

A set of tubes should last at least 5 years if they are not abused. I don't see a problem.

Thanks Altec and Mahansm for the responses. Altec, I didn't realize tubes lasted that long. I think that may be the way to go.

Don

Actually I was being quite conservative in the length of time tubes can last. For example, several years ago I bought an original McIntosh C11 preamp which had it's original 1962 tubes - and they still work fine. In my power amplifiers, the output tubes routinely have lasted me 10 years, and the input tubes have lasted at least 15 and still counting.

The length of time output tubes last is completely dependent on the setting of the bias current. If your amplifiers have user adjustable bias, you should make sure that it is never set to more current than the manufacturer recommends. In many instances, the current running through the output tubes can be set slightly low (something like 10-15%), with remarkable increase in the life of the tubes - in some instances, decades.

So no, tubes are definately not something you have to change every year, or even every 5 years.

I'm aware of what some high end manufacturers say, essentially that you have to change output tubes every 6 months or somehow they degrade to the point where they sound "bad". That is pure BS.