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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Daniel Mock on March 16, 2012, 02:07:25 AM

Title: Portable Generator Suggestions?
Post by: Daniel Mock on March 16, 2012, 02:07:25 AM
I do a lotta desert gigs and I usually rent a Honda EU 6500 from my buddy for only $250. Problem is he's selling it. So I'm gonna have to rent generators from elsewear or buy one.

Any recommendations on good generators to rent?
Last time I was in the desert my rig didn't exceed 1600w, so I think I would be fine with a 4000w generator.
Title: Re: Portable Generator Suggestions?
Post by: g'bye, Dick Rees on March 16, 2012, 09:42:02 AM
I do a lotta desert gigs and I usually rent a Honda EU 6500 from my buddy for only $250. Problem is he's selling it. So I'm gonna have to rent generators from elsewear or buy one.

Any recommendations on good generators to rent?
Last time I was in the desert my rig didn't exceed 1600w, so I think I would be fine with a 4000w generator.

Buy it from him.  Or find another one like it.  You can't beat the Hondas in that size.
Title: Re: Portable Generator Suggestions?
Post by: Stuart Pendleton on March 16, 2012, 09:51:35 AM
+1. Buy it from him. I love my Honda.
Title: Re: Portable Generator Suggestions?
Post by: john sanders on March 16, 2012, 10:14:40 AM
Check out the entire line of Honda's EU line. I believe they make a 2000watt, which I have had great success with as well as a 3000/3500 watt version.
Title: Re: Portable Generator Suggestions?
Post by: Tomm Williams on March 17, 2012, 12:41:50 AM
I 've heard from more than a few folks that Honda's are about the only gas genny that's voltage regulators are reliable enough for audio gear.
Title: Re: Portable Generator Suggestions?
Post by: Kenny Deal on March 17, 2012, 06:31:59 PM
I am no expert but something I was told one needs to consider is something about the sine wave or the cycles. Older generators can mess with newer electronics or something like that. I did not undwerstand it but I can tell you Honda makes an EU3000i I think. It's bucks but man talk about whisper quiet...
Title: Re: Portable Generator Suggestions?
Post by: John Lackner on March 28, 2012, 06:12:06 PM
An important question - does the genny put out a TRUE sine wave or a MODIFIED sine wave. A genny with a true sine wave is the only choice for audio. do your research before buynig. Or renting
Title: Re: Portable Generator Suggestions?
Post by: Nick Enright on March 28, 2012, 08:27:11 PM
An important question - does the genny put out a TRUE sine wave or a MODIFIED sine wave. A genny with a true sine wave is the only choice for audio. do your research before buynig. Or renting

While I agree, I'd like to know why.

All of the audio devices that I know about use a either a transformer and linear power supply, or a switch mode power supply. In each case the AC lines voltage is converted to a DC rail, or supply voltage suitable for the application.

A linear power supply passes the 60hz AC wave through an iron and copper x-former. This usually steps the voltage down, then the lower voltage is converted to pulsed DC and sent into a capacitor bank that acts essentially as a massive low pass filter. The ripple left after this can be smoothed further depending on need. This DC (essentially, the ripple should be very low in frequency at this point) voltage is then changed into various voltages for the circuits.

A switch mode power supply converts the incoming AC into DC, then into a very high frequency wave, that is passed through a (much smaller) iron and copper x-former, converted to pulsed DC, then passed into a capacitor bank, another low pass filter, then converted to the required DC supplies necessary for the device.

In both of these cases I cannot see how a stepped AC voltage is any different than a pure sine wave. While the stepped voltage will have more noise, that should be filtered, the duty cycle at each voltage step should be similar enough (to a sine wave) to only loose a small amount of efficiency in the x-former.

Admittedly I know way more about linear supplies, but I just cant figure why audio devices would see a difference if the AC is a step function or a continuous one.

Title: Re: Portable Generator Suggestions?
Post by: John Lackner on March 28, 2012, 09:38:52 PM
You will hear the difference right away, in the form of noise. Lots of buzzes.
Title: Re: Portable Generator Suggestions?
Post by: g'bye, Dick Rees on March 28, 2012, 09:40:33 PM
You will hear the difference right away, in the form of noise. Lots of buzzes.

Just buy the Honda Ei series and don't worry.
Title: Re: Portable Generator Suggestions?
Post by: Nick Enright on March 28, 2012, 11:52:38 PM
You will hear the difference right away, in the form of noise. Lots of buzzes.

That's not the question, the question is now, why?
Title: Re: Portable Generator Suggestions?
Post by: Tim Perry on March 29, 2012, 11:19:00 AM

Admittedly I know way more about linear supplies, but I just cant figure why audio devices would see a difference if the AC is a step function or a continuous one.

Nick, are you familiar with "dimmer buzz" issues? you would think maybe that all the power supply filtering would take care of that but sadly at times the audio system as a whole is affected.

If you have ever had a frantic time just before a show swapping cables, reconfiguring equipment, and adding inline transformers to eliminate or reduce hums buzzes and whines  you will understand why someone who has gone through it would make recommendations for 'true sine wave' power sources.
Title: Re: Portable Generator Suggestions?
Post by: Nick Enright on March 29, 2012, 06:58:50 PM
Nick, are you familiar with "dimmer buzz" issues? you would think maybe that all the power supply filtering would take care of that but sadly at times the audio system as a whole is affected.

If you have ever had a frantic time just before a show swapping cables, reconfiguring equipment, and adding inline transformers to eliminate or reduce hums buzzes and whines  you will understand why someone who has gone through it would make recommendations for 'true sine wave' power sources.

Since I switched to all balanced audio connections, bring my own power, and use single point ground schemes, I haven't ever had a buzz, even when the dimmers were almost on top of the snake, and the DMX was running down channel 42.

Occasionally I'll get a light buzz from a DI'd instrument, but that can be fixed by the specific ground lift.

Maybe I'm just lucky?

Title: Re: Portable Generator Suggestions?
Post by: Chris Clark on March 30, 2012, 01:58:29 AM
and the DMX was running down channel 42.
Not totally on point, but as long as all your snake lines are properly balanced and shielded, you shouldn't get any crosstalk from the dmx signals. Since DMX is basically a constant digital RS-485 signal at its roots, the active dimming of lights wouldn't change the signal being sent through the snake anyway. I too have done this before with no problem.

The typical problem with hum in a sound system from lighting dimmers tends to come more from the actual dimmers themselves - typically the construction of the dimmers will determine this, though anything that isn't properly wired/grounded could still cause backfeed into the sound system if they're on the same power source.