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Inverter encounter distortion and workaround ideas?
Old 4 weeks ago
  #1
Here for the gear
 

Inverter encounter distortion and workaround ideas?

Had my first encounter last weekend with running my PA on an inverter. Result was a breaking-glass distortion in the high end. Got through the gig by pulling the high end down to a reasonable level, but obviously the sound was still far less than stellar.

Ashly MX-508 mixer feeding a QSC PLX-1802
(Kill-a-watt shows entire PA, including digital reverb, AD202, and 1963 Gibson Falcon tube amp draws: 165W idle, 185-250W under load)

Inverter: "pure sine" or "true sine" off-brand rated at 600W cont / 1200W peak
( I'm assuming at least an attempt at a notch above a simple "modified wave")

My thinking at the time was likely the power supply in the PLX was not happy with the waveform from the inverter, and after some reading on the subject, my thoughts are still down the same line. The ultra-lightweight PLX has a switching PS, so...

Obviously, for me to know if any changes I make have solved the issue, I'll have to purchase my own inverter, see if I can replicate the issue, then check theory and changes in practice. I would hate to purchase a Xantrex Prosine just to find out nothing changes. (they're not inexpensive)

So my thinking at this point: Purchase a vintage Crown PS-200 or PS-400, recap it, and see if it runs on an inverter without issue. An old-fashioned transformer-based PS, I would think, would run just fine - maybe even on a lesser quality inverter...

Or am I barking up the wrong tree; There are quite a few discussions online in which users report no issues with a quality inverter such as a Xantrex (but not sure if any are running PLX series power amps) I also did not think to take the kill-a-watt and watch the VOLTAGE during the performance (dang).

I also can't be sure the distortion was coming from the PLX; It may have been the mixer, or effects.
Thoughts?

Last edited by Goldenvoice; 4 weeks ago at 08:26 PM..
Old 4 weeks ago
  #2
Lives for gear
 

I don't see how an inverter could realistically cause high frequency distortion; I think the cause lies elsewhere. What would be more likely would be general interference and picking up noise/hum and that sort of thing.

Generally speaking, switching power supplies are much less sensitive to power line quality than linear power supplies. The main difficulty with switching power supplies and MSW inverters are those power supplies with active power factor correction which in many implementations assumes the input voltage is a nice sine wave and works to force the current waveform to match, which makes them work a lot harder with something like a MSW input and can cause the devices doing the power factor correction (transistors of some sort or another, typically) to overheat and/or die.
Old 4 weeks ago
  #3
Here for the gear
 

Gig is a Farmer's Market. I've been by the market before, and the entertainment always sounds bad; part of what made me want to go give 'er a shot.
Response was overwhelmingly positive, and even though I was able to produce a sound far superior (according to all accounts) from what others have achieved, I am left with the feeling I wouldn't want to subject my gear to such [abuse?] again. The pay is small, but the exposure good for the area.

It's really about furthering my understanding of what is happening and why - more tools in my toolbag.
Simple conclusion may be: since all systems are apparently handicapped on "their" deep-cycle / inverter, the "first guess" answer would be to show up next time with a better quality inverter, and see what happens... for that matter, if I purchase a better quality inverter, I'll already know the result.

Being in the business to make money: a couple gigs there next season would pay for a used Xantrex off eBay - for a break-even scenario financially, but achieve good exposure, and be far more fun, since I won't be half concentrating on the PA. And at the pay offered, I did it just for fun anyway (which it was).

Always hard to put a price on the "exposure" part...
Old 4 weeks ago
  #4
Gear Maniac
 

If you really want to get to the bottom of it then you need to run some diagnostics through your chain.

REW has some good tools for detecting distorion and harmonic distortion.

Did you monitor via headphones and see if the issue was in the cans too?

spending money and not fixing the problem would be a shame. Find out whats causing the problem first.
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