Tube amps and low impedances

Typically tube amps maintain the same power output at all impedences. It doesn't double or halve as you go up and down as can happen with high current ss amps.

When a speaker dips to 1 or 2 ohms...does a tube amp such as the ARC 500 wpc model listed above begin to strain?.... or do they hold steady and maintain authority over the speaker?

I wouldn't recommend using a tube amp for speakers that dip to 1 or 2 ohms. That is enough of a struggle for a well built SS amp. A speaker with a nominal impedence of 4 ohms, with a dip down to about 3 ohms is about as much as you can expect from a tube amp.

Most tube amps have impedance matching output transformers built into them. You have to select the most appropriate impedance tap for your speakers and it "should" produce rated power into that load. Having said that, there aren't any speakers that i know of that maintain a steady state non-reactive load that is of a consistent impedance. As such, the output transformer is somewhat of a buffer, but power output WILL vary even with it in place.

As a side note, many tube based amps do fall off in power as impedances are dropped, especially at the very low impedances that you mention. If i was going to run a pair of VERY low impedance speakers with a tube amp, i would probably look into the Mesa product line. Since they build / design professional tube based amps, they know how to compensate for very low impedance loads. Whether or not you like the sound that their circuitry produces is a personal thing, but at least you wouldn't really have to worry about straining / blowing up the amp or tubes all the time. Sean
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