Technical explanation of inverter noise?

FoRNiK8ToR · 02-28-2006, 07:22 PM

I’ve seen plenty of threads saying that inverters will add noise to your system and DC-DC is better, yadda yadda yadda. But I was just curious as to how exactly using an inverter induces noise into your speakers? Technically, how does the noise manifest itself into the speakers? People recommend a pure sine wave over a modified one as a way of eliminating that noise… I don’t technically see how that would help? I’m not saying that I don’t believe it, but I just don’t understand how modified sine waves powering the system would manifest their inaccuracies in the speaker outputs whereas a true sine wave inverter wouldn’t?

It looks like of the few here that have chosen inverters over DC-DC, it’s seemingly random as to whether or not they’ll experience the added noise in their system. So I was just wondering if it is truly “random” or if it’s a function of proper grounding, proximity to other electronics, etc? maybe all of the above?

numbers · 03-01-2006, 03:38 AM

Inverters tend to raise the chance of having a noisy system because of the fact that they put high voltage ac in close proximity to everything. The actual way that the noise gets to the speakers is that electromagnetic interference is radiated from the ac devices and wires and somehow finds it's way to audio wires. If the audio wires are too close, or if they have ****ty shielding, or if they are improperly grounded, they are more likely to pick up that interference and carry it to the speakers. Dc-dc setups also produce emi, but it is a fact that there will be more emi present around an inverter setup than a dc-dc setup. What it all comes down to is just how much of that emi is finding it's way into your audio cables.

Folks who say pure sine wave inverters are better for carpcs are saying that because they saw that someone else said it. That someone said it because he heard someone else say it.... I don't know exactly who first said it, but they're not entirely right.

Folks who blame their noisy setup on their inverter need to learn a bit more in the area of keeping emi out of their audio cables.

Motorcity · 03-01-2006, 04:10 AM

Quote: Originally Posted by numbers

Inverters tend to raise the chance of having a noisy system because of the fact that they put high voltage ac in close proximity to everything. The actual way that the noise gets to the speakers is that electromagnetic interference is radiated from the ac devices and wires and somehow finds it's way to audio wires. If the audio wires are too close, or if they have ****ty shielding, or if they are improperly grounded, they are more likely to pick up that interference and carry it to the speakers. Dc-dc setups also produce emi, but it is a fact that there will be more emi present around an inverter setup than a dc-dc setup. What it all comes down to is just how much of that emi is finding it's way into your audio cables.

Folks who say pure sine wave inverters are better for carpcs are saying that because they saw that someone else said it. That someone said it because he heard someone else say it.... I don't know exactly who first said it, but they're not entirely right.

Folks who blame their noisy setup on their inverter need to learn a bit more in the area of keeping emi out of their audio cables.

umm, I don't know about all of that.
Pure sine wave inverters produce clean, steady, reliable ac current, comparable to the mains going to your house.
The noise everyone talks about is due to the lesser quality modified sine wave inverters being cheap and not producing a clean current.
True, the location of the ac wires will have some effect, but the majority of the nosie is due to the inverter itself.

reference:
http://www.donrowe.com/inverters/inv....html#modified

numbers · 03-01-2006, 06:17 AM

Most here do not. That is why I posted.

Clean, steady, and reliable are three things that have absolutely nothing to do with the difference between a modified and true sine wave. Try to find a reference that wasn't written by someone who has something to sell you.

The noise that everyone talks about is due to lesser quality audio installation jobs using crappy cables and poor routing technique. A modified sine wave is in no way of lesser quality or any less clean. It is just a different type of wave. That is all.

The suggestion that noise travels through the power cable, through the psu, through the motherboard, through the sound card, and through the speaker wires to produce noise in the speakers is nonsense and reveals a severe lack of fundamental knowledge by the suggester concerning such things as sine waves, inductance, emi, switching power supplies, and just alternating current in general.

roadhog · 03-01-2006, 07:37 PM

In clarification of the above, isn't it something to do with the high frequency switching which inverters do to jump the voltage up? And why don't the inverters for LCD backlights have the same effect (in general)?

numbers · 03-01-2006, 08:04 PM

Yes.

They do, but the frequency is much much higher, severely reducing the noise effect.

waltsongs · 03-03-2006, 11:45 AM

Actually, a modified sinewave inverter puts out something more like a square wave. A square wave contains a base frequency of 60 Hz and multiple odd harmonics. It' these harmonics that cause problems because they extend well into the audio frequecy range, and show up as noise on any unsheilded audio cable or trace. They can also ride on the computer's powersupply lines because the filtering is not designed to handle signals in this range. As mentioned above, good single point grounding and audio sheilding can elimate a lot of problems. Most DC to DC converters operate at 250 Khz or above so any noise that does radiate is too high in frequency to be picked up and broadcast by your soundcard and amplifiers.

That's my 2¢ on the subject anyway

Walt

EricE · 03-03-2006, 01:10 PM

Quote: Originally Posted by waltsongs

Most DC to DC converters operate at 250 Khz or above so any noise that does radiate is too high in frequency to be picked up and broadcast by your soundcard and amplifiers.

Besides. 50Khz is above human hearing. Maybe a dog could hear it.

numbers · 03-03-2006, 01:31 PM

A modified sine wave will produce more interference than a true sine wave, but that does not make it any less clean or reliable. The practice of keeping that interference out of your audio is the same as always. It isn't that complicated.

silveralt · 03-03-2006, 02:56 PM

I had a modified sine inverter hooked up to my cig lighter and had interference when my car was wet. I hard wired it to the battery and had no problems and still have no problems ever. I think it is a grounding issue with it.

amthar · 03-03-2006, 03:38 PM

This thread is fascinating (no sarcasm there)

Simbo · 03-05-2006, 07:45 PM

Just a quick comment.

anyone who has a modified sine invertor.

Plug your pc into the mains, and check the temperature of the PSU. Then do the same with the invertor.

You'll find that off the invertor it will probably run very warm to hot in comparison with the mains, some PSU's even "sing" when running off an invertor.

The problem arises because both the invertor and the PSU are both switched mode power supplies, and the harmonic noise from the invertor "annoys" the computer PSU (different switching frequencies).

Anyway, The Opus is cheap enough, buy one, they work!

waltsongs · 03-07-2006, 09:36 AM

Quote:

You'll find that off the invertor it will probably run very warm to hot in comparison with the mains, some PSU's even "sing" when running off an invertor.

This is because the harmonics associated with a non sinusoidal inverter represent wasted energy. They have to be dissipated somewhere. If you can afford an Inverter with a sinusoidal output, buy it. If you can afford a DC to DC that will power your setup, that’s even better.

MatrixPC · 03-07-2006, 03:34 PM

When I used inverter setup. I have NO audio noise, engine whine or any similar noise. The only noise that I can hear is one that coming from the AC PSU (harmonic). The only time I can hear that noise is when the engine is NOT running and totally silence. Once the music is play, there is NO noise cuz music is much lounder than that harmonic noise.

lbergamo · 05-13-2009, 09:45 PM

Quote: Originally Posted by numbers

Inverters tend to raise the chance of having a noisy system because of the fact that they put high voltage ac in close proximity to everything. The actual way that the noise gets to the speakers is that electromagnetic interference is radiated from the ac devices and wires and somehow finds it's way to audio wires. If the audio wires are too close, or if they have ****ty shielding, or if they are improperly grounded, they are more likely to pick up that interference and carry it to the speakers. Dc-dc setups also produce emi, but it is a fact that there will be more emi present around an inverter setup than a dc-dc setup. What it all comes down to is just how much of that emi is finding it's way into your audio cables.

Folks who say pure sine wave inverters are better for carpcs are saying that because they saw that someone else said it. That someone said it because he heard someone else say it.... I don't know exactly who first said it, but they're not entirely right.

Folks who blame their noisy setup on their inverter need to learn a bit more in the area of keeping emi out of their audio cables.

I am open to suggestions. I found placing random connections to the vehicles ground along the path of the audio eliminates msjority of the noise but not all especially when it comes to the microphone setup. As an example when I record audio using something simple like windows sound recorder I can hear the noise in the recording. Any help would be great.

Leo

P.S. I am no electrical engineer that is why I read these forums. I only know enough to hurt myself.

User Name		Remember Me?
Password