VariAc as attenuator

[Eamonn]

I distinctly remember an interview with Eddie Van Halen where he sais HE used a Variac in this manner.(late 80's Guitar World magazine, Ive got it here somewhere!) The interview also had a warning from the editors "not to try this at home." How did Eddie get away with it? It appears from what's posted here to be a very bad idea.

[vibratoking]

I distinctly remember an interview with Eddie Van Halen where he sais HE used a Variac in this manner.(late 80's Guitar World magazine, Ive got it here somewhere!) The interview also had a warning from the editors "not to try this at home." How did Eddie get away with it? It appears from what's posted here to be a very bad idea.

No, Van Halen used the Variac in a completely different way than the discussion in this thread. He used it between the mains and the power cord of his amplifier to reduce the AC voltage supplied to the amplifier.

This is not the same as placing it between the amplifier output and the speaker.

[Cliff Schecht]

You're right rd, that would match it correctly, but you'd need a 16. I was responding wrt a 4 and an 8.

You could put the two speakers (4 and 8 Ohms) in series and run them on the 8 Ohm tap..

This variac idea is a misguided one IMO and while I'm all for misapplication of parts and such, it's only good to do so if one actually understands what principles they are exploiting. A variac is a big transformer that can be a perfect 1:1 match and vary all over the place from there, but I immediately see bandwidth issues with using a variac as an attenuator (it's an impedance, not purely resistive, and so there exists a frequency component that we don't usually deal with in using attenuators).