how can I filter noise I get laptop audio out from car inverter?

JBI

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Feb 23, 2018, 10:22:38 AM2/23/18

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I am using a standard 400 W 12 VDC to 120 VAC inverter to power my
laptop in the car. While this works well, lately I've started doing
audio work with the laptop and feeding the laptop 1/8" audio jack output
into an amp hooked into the car radio. While the laptop is plugged into
the inverter, I get much noise over the audio system. I know the noise
is coming from the inverter, so how would I negate it? I've tried about
5 snap closed ferrite cores around the power cable going into the laptop
but they haven't helped. Thanks.

Sjouke Burry

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Feb 23, 2018, 12:40:53 PM2/23/18

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A differential amp, to get rid of a ground loop.

Or feed both devices from the same minus 12v point.

Or both.

Tim R

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Feb 23, 2018, 1:38:57 PM2/23/18

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You've tried it with good headphones, right?

Jeff Layman

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Feb 23, 2018, 2:06:35 PM2/23/18

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Have you considered using a direct supply with an input of 12v and
output to suit most laptops (19V? You didn't say which make you have).
Typical example here, but many others available at all sorts of prices
and quality:
<https://www.ebay.com/itm/Universal-DC-15-24V-Car-Auto-Charger-Adapter-Power-Supply-for-Laptop-Notebook-PC/191191789071?epid=560493099&hash=item2c83eb2e0f:g:FEwAAMXQ1ZhThFqB>

Hopefully, although also a SMPS it will not produce the sort of
interference you are getting from your 12/120V inverter.

--

Jeff

Terry Schwartz

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Feb 23, 2018, 3:45:17 PM2/23/18

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Get rid of the inverter. They are all horrendous noise sources. Run on battery.

Gareth Magennis

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Feb 23, 2018, 5:10:41 PM2/23/18

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"JBI" wrote in message news:p6pbjo$kkr$1...@dont-email.me...

*****************************

Well the best bet is to use the laptop battery when noise is critical.

Gareth.

Ralph Phillips

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Feb 24, 2018, 3:33:10 PM2/24/18

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Use a 12V supply for your laptop?

For my Dell Lattitude D630, I can use one like this:

https://www.ebay.com/itm/DC-Car-Air-Charger-for-90W-Dell-Laptop-D09RM/262961901405

RwP

gregz

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Feb 25, 2018, 4:32:32 AM2/25/18

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I don't know the problem, but a transformer isolator may help or work.

Greg

Adrian Caspersz

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Feb 25, 2018, 9:36:47 AM2/25/18

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On 23/02/18 15:22, JBI wrote:

Has the laptop & car audio got bluetooth?

--
Adrian C

mako...@yahoo.com

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Feb 26, 2018, 3:29:58 PM2/26/18

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> >
> A differential amp, to get rid of a ground loop.
>
> Or feed both devices from the same minus 12v point.
>
> Or both.

or an audio transformer to break the ground loop

mako...@yahoo.com

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Feb 26, 2018, 3:31:57 PM2/26/18

to

> >
> A differential amp, to get rid of a ground loop.
>
> Or feed both devices from the same minus 12v point.
>
> Or both.

or see if you can find a 12 to 19V ISOLATED power supply.

Isolated means the input and output grounds are not connected, This will also break the ground loop.

bruce2...@gmail.com

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Mar 20, 2018, 11:28:54 PM3/20/18

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As is the car itself or anything else operating near it.

> Run on battery.

Clifford Heath

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Mar 21, 2018, 8:23:18 PM3/21/18

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Not all of them. Unfortunately price is no indication however.
We've used quite a few different inverters for our in-car
fox-hunting gear, and some cheapies are quiet, some $$ are
noisy. You just have to suck it and see in most cases.

No, I don't know brands and models - been away from this for
a few years.

> As is the car itself or anything else operating near it.

Cars can produce lots of interference, or next to none.
At least with a car you can usually chase down the cause
and perhaps cure it.

Clifford Heath.