Tech: Amp : Battery Model or Mains+Inverter

Subject: Tech: Amp : Battery Model or Mains+Inverter
From: Ian Hendrie
Date: 17 Apr 12 - 11:03 AM

The battery powered Roland AC33 amp looks to be very useful for playing outdoors and, as I am very impressed with the mains operated AC60 which I own, I am considering its purchase. I am slightly put off by the fact that it only operates with a power of 2x10w with batteries when its headline description states 2x15w (slightly misleading advertising methinks).

As my outdoor use is likely to be on the canal towpath next to a boat (with 12v power) could I use the mains model (AC60) SAFELY through an inverter and would I be better off with a pure sine wave model (expensive) rather than a cheaper quasi sine wave one. I have a friend who 'fried' a couple of TVs and this was put down to the cheaper inverter. I don't want to take any chances of damaging the amp.

Can anyone technological allay my inverter fears or would I be better off opting for the battery powered AC33?

Comments please.

Subject: RE: Tech: Amp : Battery Model or Mains+Inverter
From: JohnInKansas
Date: 18 Apr 12 - 01:33 AM

If you're afraid of the direct inverter connection, you might consider putting a UPS (emergency/backup computer power) box in line with it. Power clean enough for a computer shouldn't harm your amp. You might need to do some rewiring on the UPS to get what you want, although there are some "full time conditioned power" boxes available. I'm not current enough on specs to guess about the $$$ or €€€€ involved.

Unfortunately, you can expect up to 30% loss through the inverter and 10 or 15% (at least?) through the UPS, so it might be more drag on the boat supply than you'd want.

There are very "clean" inverters available, but unfortunately the honest specs on a clean one look about the same as the published specs from Liars Inc. so it's hard to pick.

John

Subject: RE: Tech: Amp : Battery Model or Mains+Inverter
From: Ian Hendrie
Date: 18 Apr 12 - 04:11 AM

Thanks for that John.

The UPS boxes I've looked at so far cost £70+ here in the UK and seem designed solely for computer use. I don't think I want to be rewiring anything so I'm thinking that a pure sine wave inverter alone (£80 for a 150w version) may be the answer. It would be powered from a bank of 3x12v car batteries only when they were not being charged by the engine, i.e. engine stopped. There shouldn't be any spikes or surges under these conditions (I would hope) and anyway, I could use a spike protection socket. The inverter has a low cut-off at 10.5v but I would hope that if my batteries were in good condition this shouldn't be a problem even if the inverter is some distance (15m) from them.

Again, I'd be very happy to hear comments.

Does anyone regularly use a 12v inverter to power a PA.

To add another problem. I have occasionally plugged my PA into power provided by a generator (not mine). Am I taking a risk of damaging the PA when I do so?

Subject: RE: Tech: Amp : Battery Model or Mains+Inverter
From: JohnInKansas
Date: 18 Apr 12 - 06:05 AM

I'm not sure of the exchange rate, but 80£ for a 150W inverter sounds a little high. The difference in line voltages and frequency here and there may account for quite a bit of the difference I'm imagining though. And there's probably some effect from the VAT(?).

I've got a 300W inverter that claims <1% distortion that I bought for around $40 US a while back, and a 500W with similar specs that cost me less than $60 US.

Some of the inverters they were selling here 10 years ago were pretty close to square wave output, but most of what's available in the auto/camper supply shops now are clean enough to run anything I've even thought about hooking up to one.

Generators vary some in their output quality, but the only precaution recommended by the makers I've looked at is that "delicate" equipement should be plugged in only after the generator is up to speed and "stabilized," which usually means a few seconds after it quits burping on the richer mixture often used for starting. The generators produce their output from a "rotating machine" that assures a pretty sinusoidal waveform, even if the machinery is crude, although the frequency of the output may not be exactly "primary time standard" quality.

The people who bring generators to the festival campgrounds here generally only have them so they can watch TV (US football games mustn't be missed of course), and most of them bring a satellite dish & converter. I haven't heard any complaints about blowing that kind of equipment with a generator - or with inverter power.

John

Subject: RE: Tech: Amp : Battery Model or Mains+Inverter
From: JohnInKansas
Date: 18 Apr 12 - 06:06 AM

Subject: RE: Tech: Amp : Battery Model or Mains+Inverter
From: JohnInKansas
Date: 18 Apr 12 - 06:07 AM

I'm not sure where that blank post came from. It wasn't anything I intended to be doing.

John

Subject: RE: Tech: Amp : Battery Model or Mains+Inverter
From: Big Al Whittle
Date: 18 Apr 12 - 06:13 AM

A few years ago in the display hall at Fylde - there was a bloke selling guitars and he had an AER amp that you could run by battery and I thought that looked pretty cool. You had to recharge it on the mains. Maybe if you were sailing past a pub they would recharge it for you for a couple of quid.