amplifier power consumption

I would be hesitant to use even the 540W ups, without knowing the exact power requirements of your particular amp.

Here is a Cambridge integrated amp rated 75W/channel and spec'd for a maximum power consumption of 600W.

Here is a Creek integrated amp rated at 80W/channel and spec'd for 340W consumption at full power.

So the numbers can vary widely.

Also, I would want to derate the ups capability by a factor of 2 or more (meaning its rating should be twice the expected worst case requirement) to allow margin and to minimize the possibility of affecting dynamics.

Keep in mind, too, that some ups's, especially the inexpensive ones, put out quasi-square waves instead of sine waves. You would want to be sure to get one that puts out true sine waves.

Re the wattmeter that Riley linked to, I would question whether or not it will capture and display very brief peaks in power demand, which is what is important for your purposes.

Regards,
-- Al

To repeat Rog's response it should give the info on the back of the unit. Usually near the AC power inlet...

As Al said make sure the UPS puts out a true sine wave. SCRs will give you at best a 12 step wave (12 pulse). Cheapo Battery Back Up UPS a square wave, horrible for audio equipment.

The only true UPS units on the market today that I know of uses IGBT technology.
*Undistorted waveform (low harmonics)
*Fast switching speeds (100% step loads)
*No ripple DC (long battery life)

A True On Line UPS unit takes the AC incoming power and converts it to DC then converts it back to AC.

A True On Line UPS unit using IGBT technology cost quite a bit more $$ to buy than an SCR based unit.

Just to further Almarg's & Jea48's point re. ensuring that you buy a UPS with a true sinewave output - I understand that some friends bought an UPS that did not (i.e. output a sq. wave) & they were not aware of this & it fried the electronics over a short period of a few months.
So, be very careful of the output waveform. Most of the time UPSs are targeted to PCs that use switching power supplies hence it does not matter but to audio electronics sq. waves are bad news. APC has come out w/ an audio version UPS but I believe that it's not cheap.

Your best bet would be to buy a PS Audio unit OR a (Canadian) PurePower unit. The PurePower has a battery backup while I believe that The PS Audio units do not.

Rrog, my amp has been modified and puts out more power than it did in its original state, but i will look on the back of the amp anyway (hadn't actually thought to do that! duh!)

Riley - thank you very much - I may just go out and pick up one of those!

Almarg and Jea48 - I appreciate your advice as well (and will pay heed to your warning about the unit not measuring peaks).

by the way -

Stangely, a very good service technician whom i know suggested using even the CHEAPEST one by a company called APC (the unit that puts out 200w). He states that he has all his equipment (all tubes) ALL connected to it (amp, cd player, tt) and that it 'does the same job as the more expensive ones', therefore 'you don't need anything more'. I asked him several times if he's sure... and he insisted it was more than fine for my application.

His statements really confused me, to be honest, since it doesn't seem to make all that much sense to me. Then again, i'm not an electronics technician.