View Full Version : Using a UPS for amplifier power

Don Mascali
01-24-2005, 05:23 AM
I asked a question in this thread as a side note but no one has addressed it.


I have been using a big 1500 VA APC UPS that I got at work. I would like to know what people think about it.

I have 4 Yamaha Pro amps pluged into this thing. My thinking is that it has good surge and spike protection and has a battery back up that will pick up the power when it droops also. When a loud transient passage pulls down the amps that it will help maintain the amps power supply.

Can anyone come up with knowledge or an educated guess on this? Thanks.

scott fitlin
01-24-2005, 11:40 AM
I like my amplifiers plugged directly into the wall! UPS, and Power Line conditioners can tend to limit the the current, and amps draw current, lots of it, instantaneously! I have found that plugging my amps into a power filtering device softens the dynamics!

Play with it and see what you find! I plug my amps into the wall with nothing in between!

Alex Lancaster
01-24-2005, 03:03 PM
:) Don: The problem with UPS's and conditioners, is that they use a switching power supply which puts out a modified square wave; A computer doesnīt care, it is digital, but Your Amps sure do.

01-25-2005, 09:06 AM
Scott and Alex I understand your reasoning in not useing power line conditioners for amps. Would this also apply to other audio equipment (preamps, tuners, cd players etc) ? Would a common surge protector strip be sufficent for the preamp/tuner/cd etc? I'm useing two Adcom 515 conditioners that are very "convenient" for powering on/off all my audio equipment/tv.

scott fitlin
01-25-2005, 04:16 PM
If you like the effect of PL conditioning and filtering etc, you use it on front end components! Pre amps and EQ,s etc, dont draw lots of current and wont be adversely affected, unless you just dont like what it does to your sound! But thats another story!

Power line conditioners can be used for front end!

Alex Lancaster
01-25-2005, 06:36 PM
:) As I mentioned, most UPSīs and PLCīs, put out a wave that might go thru Your power supply, front end or amps; The real expensive sine wave generators are another story.

I would not use inexpensive computer UPS or PLC's except on my computer.

01-25-2005, 11:40 PM
From my own experience, I considered using a UPS as a combination surge protector and something to cleanup the AC sine wave. After looking into them, I found out that there are two types of UPS's. The inexpensive ones typically bypass the battery during normal operation such that there's no AC-DC-AC converting/inverting going on. So all you end up with a really is a relatively expensive surge protector. The more expensive UPS's do run all the power thru the back up battery and go thru an AC-DC-AC converting/inverting process all the time. But unless you're willing to spend megabucks ($1500+) for top-of-the-line, true sinewave units, the AC sinewaves they put out, as Alex mentioned above, are squared off and not necessarily good for your equipment.

So instead, I purchased a PS Audio P300 power regenerator, for about $600 used. This essentially takes the AC power from the wall, converts it to DC and then inverts it output a true AC sinewave. The cleaned up AC is supposed to produce "a bigger soundstage, lower noise floor, blah, blah blah....". Maybe it did. I don't know. But my old ears couldn't tell a big difference. What I did know is that the unit took up a lot of space, put out a lot of heat, and could only handle an output of about 300 watts although PS Audio made larger capacity models to accomodate amps. After selling that I purchased a PS Audio Ultimate Outlet, High Current model, for about $275 used. These provide basic AC filtering and surge protection. Because of the number of lightning strikes in my area (and fact that lightning took out my tube amp once) I felt the need for some sort of surge protection but didn't want it to degrade the AC. I think the sound is a little cleaner with these Ultimate Outlets but it's a very subtly difference if at all. At least the sound is not degraded. And there's no limit to the amount of current you can run through them.

Just like speaker cables and interconnects, there's no limit to the amount of money you can spend on power conditioners. But also like cables and interconnects, after a certain point, spending more money doesn't always improve the results. The key is to find that happy medium.

01-26-2005, 02:27 AM
I agree with everything that's been written here. A square wave UPS on a power amp is a bad plan. The extra harmonic energy present in a square wave is not intended to pass through a 50 or 60Hz power transformer. As it can't go through it ends up being dissipated as heat in the transformer.

This is a bad situation for any piece of gear with a power transformer. In fact the situation could be worse for front end gear. Power amplifiers used in the home are rarely if ever used at full power giving a lot of spare thermal capacity in the transformer. Front end equipment often uses a transformer near it's full capacity giving little extra capacity to get rid of the heat caused by the harmonics of a square wave input.

Personally, I wouldn't use a square wave UPS on any piece of equipment with a power transformer. If you're feeding a switch mode power supply (PC's and some PA power amps)-no problem as the input power feeds straight into the rectifiers.

Cheers, Ralph.

Don Mascali
01-26-2005, 07:42 AM

This is the unit I use. It has a sine wave output and also prevents voltage sags during instantaneous power demands.
I just feel that the rack I use has so much equipment that it would have a hard time keeping up with the demand.
I use a Furman rack mount unit with extra RFI for the digital stuff and the power amps are plugged into the UPS.
I can't hear any sonic degradation but my ears aren't that good I guess.
After reading the various comments, I will keep things as they are. If it did have a square wave output I certainly wouldn't use it any longer.

Thanks to everyone for their input.

Alex Lancaster
01-26-2005, 08:00 AM
:) Porsche: For lightning, surges, spikes, I use Metal Oxide Varistors (MOVīs), right at the mains supply, after the fuses; I use the 130 and 250V ones as I have 3 phase service, do a google search so Youīll know how to hook them up in all modes, if the spike is high and long enough, they will explode, but absorb it, and they are dirt cheap, I even use them on the phone lines, and have had neighbors with blown faxes, modems, phones, etc., while mine were unaffected.

01-27-2005, 06:43 AM
Thanks, Alex. That's good information.

Ed S.

10-06-2006, 12:53 AM
hi don. i know this post is old,but thought i would leave my 2 cents lol.i don't think i would use the ups.as far as i know the thing doesn't actually kick in till the ac input is gone.i doubt the ups can actually pull up the voltage on a sag.if it did see a sag enough to kick that thing in i wouldn't want to be running my system at that point in time.even if the ups did come on in a sag i don't think it would support the amount of curent being used at the time so would be useless.i think it might actually make it worse because it has to switch between line and ups which would probably cause a noise to come out of the speakers as if you flipped the power off and back on.it may be useful for noise and spike supression,but i wouldn't use the ups except maybe on pc's like others have said.you would probably be better off getting a second rackmount or similar filtering unit.most of those rackmounts are usually only good for 15 or 20 amps as well as the outlet you're plugged in so you have to figure out how much your system pulls max and decide if you need another.you may consider one of those power blocks which usually only have 4 outlets with no switches and the least amount of connections involved which helps minimizing current loss.most pro-audio shops have that kind of thing or they can get it.every situation is different so you would have to figure out what you have to do to get what you want.
if you could have some dedicated ac outlets on the same leg of the breaker panel would be good if applicable to split the current draw between amps and away from your front end stuff in addition to cutting down on line noise.i don't have that luxury since i have to setup & teardown for church each week in and old school we rent.so i have to find different outlet circuits to tap in to split the current load.some of the outlets cause a little noise due to the difference in ground potential so i try to get on the one's in the same leg when i can.most of the time i can get by with just putting the subwoofers on their own circuit.i have to run between 1 and 3 ac lines depending on the setup that particular day.right now i have 3 of the basic furman rackmounts.i will upgrade later when more money becomes available. well hope this info helps someone. here are a few links i happen to know.