Jump to content
Sign in to follow this  
djdfw

PA off electric Generator, Inverter Required?

Recommended Posts

Except that the AH draw for program music is much, much lower than the power capacity of the audio amp, particularly when you are using a car amplifier.

 

My standby draw on the car amp is about 600mA. I'm only drawing the amps when I'm pushing the air. The AH draw also depends on the content of the music. If you are mostly using the horns and not pushing the deep bass, then you can run very loud with little draw because of the efficiency of the horns. Anything that depends on subs and heavy bass will suck huge amps, but many other kinds of music take much less power to run for a long time on batteries.

 

Now if you are using regular audio power amplifiers, you could be sucking huge amps just in overhead, since they are usually designed with no consideration to AH draw on batteries. For a lot of music, you do not really need more than two or four GC batteries to run for more hours than you'd want to listen. All that needs to be part of the AH calculation though, and I use my clamp-on DC ammeter to closely monitor the draw so that I can know exactly what to expect for battery draw. I never discharge below 50% in order to preserve the cycle life of my cells. A pair of 6V Golf Cart batteries last a lot longer than a pair of 12V marine deep cycle, in my experience. I too was very skeptical about the ability to run quality music at loud volumes for a long time on batteries, but I was able to address these issues to my satisifaction by experimenting with a number of different configurations to settle on my final solution. I wasn't happy with any of the battery powered amps I found to handle my needs.

Share this post


Link to post
Share on other sites

For any typical audio power amp (not car audio) the system typically draws on average between 1/4 and 1/8 the rated power of the amps where sized reasonably. 1/8 is the typical minimum and 1/4 counts for inefficiencies throughout the conversion chain including inverter, I**R loss, power supplies.

 

So take the 1/8-power currrent draw at rated power (from the manufacturer data) and double it and this will be a good estimate of the system power draw for long term energy reqts.

 

This is a good application forthe most efficient speakers you can find, and maybe car audio amps offer a bit of efficiency benefits here too but I was referring to what the OP had listed and his SPL needs.

Share this post


Link to post
Share on other sites

Yes, agedhorse, I understand the inefficiencies of the typical audio power amp, which is why I bypassed them to use car audio, which is designed to run off Automotive 10.5-15VDC power directly.

 

I found that my 1500 MSW inverter has a larger standby draw, 1A, than my car amplifier at 600mA. So even out of the starting gate, the car amp is ahead in the efficiency game. In the end, I found that the car amp eliminated all the losses due to the extra power conversions that were removed, to keep the amps pushing air instead of heating equipment.

 

I agree that if you just keep all your existing equipment that is power inefficent and runs off generators, then switching to battery/inverter alone may be impractical. But once you bring in the ability to improve the efficiency of the demand, not just the supply, then you open up a lot more possibilities. This is why people running on solar power usually choose to run much more power efficient appliances than the typical consumer models, so that it makes the whole battery/DC/panel requirements much lower than "normal".

Share this post


Link to post
Share on other sites

The actual amp losses are pretty miuch identical, the additional current is probably reactive from a linear transformer and with some inverters this will be returned to the inverter's energy storage assuming it's a non-linear converter. It's not (all) real power.

Share this post


Link to post
Share on other sites

Let's also compare apples with apples. Car audio is firmly buried in bull{censored} marketing of specifications. A "more efficient" car amp is more likely a much less powerful amp than the "equivalent" SR amp.

Share this post


Link to post
Share on other sites

Oh, I do compare apples to apples as far as actual audio output power. I use measured power, as best as I can do, not stated power. Yes, it is quite true that car audio power is grossly overstated to a point of complete bull{censored}. However, there are good car audio amps that put out respectable clean power that can be compared to lower end pro audio amps. It's hard to do a fair comparison, but I've been able to adjust for my purposes. The bottom end pro audio amps in powered mixers are almost as much BS as car audio, not quite, but close.

 

I'll even reveal that the car amp I use is an MTX Audio X Thunder 704X, which I got on clearance at a Circuit City for about $120, as I recall. I run two Peavey PR10 on separate channels and a PR15 on the side bridged mono. The amp has built in tunable band pass filters that I can use as an active crossover. Yeah, it's not exactly big time audio, but it works for me and it's a hell of a lot better than any battery powered amps/PAs I've tried, and I think I've tried just about all of them. It's not hard to improve on these battery powered products because they are all complete crap, which provided me the motivation to roll my own system. I also realize that there's a limit to how much a battery powered system can scale, but there's still a lot of situations where I can use my system to get good sound at a value price with no hassle from the power/fumes/genset/you can't set up here music police. When you run on batteries you avoid a lot of problems in public places. Bring Your Own Batteries to jam along. If I had to bring a genset to play, a lot of places would be closed off to me, particularly indoors. The Man is always looking for an excuse to shut you down, that's his thing.

Share this post


Link to post
Share on other sites

I never said it can't or won't work, nor that it couldn't sound good either. A good friend of mine was the engineer for Linear Power years back and the amp designs were just fine as were the SMPS (DC-DC converters). It's just that the marketing folks took a good thing and tried to make it better through bull{censored} numbers.

Share this post


Link to post
Share on other sites

No problem, I'm just stating what works for me, and how it might work for others instead of gensets, specifically for DJs doing remote gigs. I'm not here trying to dispute what anybody else is saying, only that I'll defend what my experience has been.

Share this post


Link to post
Share on other sites

Since we are on the subject of generators, I have a 36 ft, Motor home with a 50 amp Generator, would that work for live sound, it has 2 separate brk. a 20 amp and a 30 amp I always wondered about that. Thanks interesting subject.

Share this post


Link to post
Share on other sites

If that's an Onan genny (now part of Cummins) then it's typically a better quality product and within the limitation of the product should work just fine. For an audio load (dynamic) derate the genset to 50% of rated load to aid in regulation (both V & F)

 

Is it propane?

Share this post


Link to post
Share on other sites

I'm running 2 mixers, a 200w peavy 5 channel, and a Pyle 600w along with a 2 channel wireless uhf receiver on a 3200 watt generator. (4000 watt peak) Any suggestions? I'm having to replace my old Marshall halfstack (175 watts) , and an older peavy 5 channel 200 watts mixer today. Though I believe the marshal burnt from moisture, I'm not sure why the peavy died. It receives, but it doesn't send on any channel. I purchased the two mixers above just now and was thinking the same issue that began this thread over the use of generators with pa equipment. I've found the thread to be interesting, but I need a bit more info from more experienced ppl than myself. From what I've read I feel that the 3200 watts should be sufficient for the 800 watts of power that the mixers are pulling, but if there is any other advice, I'm certainly willing to listen. I can't afford to replace this equipment every 6-12 months if there is something I can do to protect it. Thanks!

Edited by Ministryman

Share this post


Link to post
Share on other sites

I would heartily suggest a power conditioner, as most generators output is not particularly 'clean'. Fine for a refrigerator or lights, but not audio gear.

Share this post


Link to post
Share on other sites

I provided the sound system for a local multi-band outdoor festival on August 5th.

A generator was provided: Predator 6500 (non-inverter).

Since the gen was a non-inverter I used my analog mixer along with my three crown amps.

No problem at all.

I am, however, hesitant to use my digital mixers on non-inverter gens...

 

Share this post


Link to post
Share on other sites

I hesitate to use anything I value on such a generator... inverter or not.

 

Something about using the cheapest generator on the planet with a pretty bad reliability history on expensive electronics. Of course your mileage may vary, but I don't care for the odds.

  • Like 1

Share this post


Link to post
Share on other sites

URGENT RESPONSE NEEDED

If I were to ride in the back of a pick with a Peavey KB300 amp and a Yamaha PSR S900 would this work using the pick ups built in 400watt inverter?

If not could I rent a Honda 2200 gas generator inverter and would that work? If not advise! 

Share this post


Link to post
Share on other sites

Could you clarify what you are asking, because as written it makes no sense to me at all...

If you are trying to power your amp from a 12VDC-120VAC converter built into a pickup truck? That will work as long as there are enough amps being generated, and a guitar amp typically draws under 2 amps, but I am not certain what the wattage consumption is of the Peavey amp, but it likely draws less than 400W; it should be listed on the amp somewhere.. Otherwise yes, you could use a standalone generator.

Share this post


Link to post
Share on other sites

this is cross poasted from diy...   already answered...  not even a thank you or kiss my grits...   

 

youre welcome, n00b!

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...