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Which variac should I use for my MC30 mono blocks?

angelaudio

angelaudio

Super Member
I did a search for this and although there is a lot of info on how to use the varias, there isn’t much in the way of what particular variac to use.

BTW Not really sure if I even need a variac seeing as how both units have been powered up within the past month or so and were working properly. One has an 18 year old rebuilt power supply and the other has a handful of replaced capacitors but has no audible issues either.

Any recommendations/suggestions would be appreciated. Thank you all!
 
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Not enough info. Were these yours when they were last powered up or were they just bought and shipped to you. If you had these before then no need to use a variac to power them unless you changed something. If you had just bought them and they were shipped to you, then you could use a variac to bring them up slowly to make sure there is nothing wrong with them.
 
Drummerboy2 said:
Not enough info. Were these yours when they were last powered up or were they just bought and shipped to you. If you had these before then no need to use a variac to power them unless you changed something. If you had just bought them and they were shipped to you, then you could use a variac to bring them up slowly to make sure there is nothing wrong with them.
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Just acquired these within the last month. They were both demonstrated to be working. I haven’t made any changes to them at all.
 
A variac will control the voltage at a level set by the dial, 0-140 usually unless the unit is a 240V unit or it wired to max at line voltage. It is used to reform electrolytic caps by stepping the voltage up every so often over a period of time finally reaching line voltage. Used with or without a DBT, one can see if there is a problem with the UUT but in your case these units under test have both been given a shot of pure line voltage and didn't explode a cap so maybe just plug em in and monitor them for a while.

The variac to use is one that can provide all the amperage the unit needs and a 30watt tube amp ain't gonna suck all the juice outta anything but the smallest variacs. a 5 amp would work, probably a 2 amp would be fine, too, but I'm not looking at the watt consumption of the amp to make that determination using Ohm's law.

If the power on for proof of work was brief and they had spent a few years sleeping maybe a voltage step up on a variac will help. I don't know but some here will. If they were on a for a period of time, you can just use them and check them to be sure.
 
If they've been run within the last month, I don't see where a variac is particularly necessary. Likely if it was going to blow up, it would have last month.

a 5 amp variac will run just about anything you're likely to plug into it. I've easily run 100 watt mono amps at full output without pegging the 3 amp meter plugged into mine.
 
I went ahead and plugged em straight into the smiley faces in the wall (aka the outlets). They’ve been running smoothly. I actually had to run out to the store and left them on so we’ll see if they haven’t done anything strange while I’ve been gone. Also while I’m here. Is it ok to switch speakers with the gain and preamp volume all the way down while the whole system is on? Or should I turn off the amps or preamp or all then switch speakers?
 
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