Variac worth the price?

[wavey63]

Now I would not blame anyone for ignoring this redundant post but I am curious. Should I invest the $100 on a variac? I am happy with my tone now but am always looking for something new. Is the variac a " plug and play" or does it require a mod? I just want a bit more squish and fatness. Ny direction would be great. Cheers!

[PCollen]

The Variac is external to the amp, between the wall outlet and the amp power plug, and so it is 'plug and play'. But the issue I have with it is that it lowers ALL voltages in the amp, including filament and bias voltages. Running tubes on lower than recommended filament voltages can be a problem, and there is no guarantee that the bias voltage and power tube plate voltages will be reduced proportionatly to maintain the same bias point..it all depends upon how your bias voltage is derived from the P/T secondary. In other words, you can measure that's going on outside the amp, but not inside the amp until you pull the chassis and take internal measurements..so that would be the first step: to document how the internal voltages in your amp change with incremental changes in the input A/C.

[wavey63]

Thanks. I was wondering if anything needed to be adjusted in the amp. That was what I meant by plug andplay.

[Ivabiggun]

Just my two cents here. I bought one from another company that offers amp kits and is a well known speaker builder who shall remain nameless. I paid about $50.00 and it works fine. However, I only use it to bring up the voltage on a repair or new build just to make sure I haven't swapped the plate and cathode wires of V1a and hitting it with wall voltage Not that I've ever done that. Also don't forget that you will need a one to one isolation transformer to protect you from shocks when it is plugged in even when it is off.


Ivabiggun