Help me fix my laptop Hiss!

pragmatic

Distinguished Member
I use a laptop as my main pc (with a dock), when this is connected in anyway to both the mains and my pre amp I get a hiss/whine through my speakers, the noise is not constant so I assume it is related in some way to the activities of the laptop.

I have this connection:

Laptop docked -> TV -> Oppo/DVD player -> Pre-amp -> Power amps -> Speakers

Removing any of these links removes the noise, essentialy if I remove the HDMI connection from the Laptop to the TV the noise ceases.

I bought a UPS thinkinking this might help things, it does and it doesn't ...
Running with the UPS plugged in the noise exists, unplugging the UPS and powering my laptops PSU from UPS battery makes the noise go away.
Similarly disconnecting the PSU and running from the laptops Battery makes the noise go away.

The whine noise is a constant volume regardless to the pre-amp current volume.

Has anyone else experienced this? The very act of plugging my laptop in causes the noise, regardless if the pre-amp share an adapter with it or they are plugged into sockets at opposite sides of the room.

Any ideas for a solution?
 

larkone

Member
So doesn't make a noise if the UPS is not connected to the mains and/or when the laptop is running off its battery. I think it safe to assume your laptop power supply is faulty in some way and is putting noise back into the mains, not surprising as it is a switched mode power supply and they can be noisy by design, unless properly designed and built. New power supplies are not expensive on t'bay, just type in the number on the laptop or the power supply and you should find a match.
 

pragmatic

Distinguished Member
Interestingly I have 2 PSU's for the laptop, one for use with the Dock and another for use with the laptop on its own, they are both as bad as each other and are different models (the dock one draws more power).

I will try another PSU, in the mean time anyone got any alternative ideas?
 

Mark.Yudkin

Distinguished Member
Interestingly I have 2 PSU's for the laptop, one for use with the Dock and another for use with the laptop on its own, they are both as bad as each other and are different models (the dock one draws more power).

I will try another PSU, in the mean time anyone got any alternative ideas?
Modern laptops are supposed to be properly designed, including "correctly grounded" PSU's.

Unfortunately, solving this when both 1) the laptop/PSU isn't adequate, and 2) you're using HDMI connectivity, is rather expensive. Basically, you need to kill the electrical connectivity over the HDMI, meaning you need an optical link, like this. For more information, see Fibre Extenders - HDMI Fibre Extenders and Distribution.

The cheapest solution is to use a "dirty" laptop off batteries for this application.
 
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pragmatic

Distinguished Member
Is it a panasonic PWD7 TV?
No a Samsung 2010 series 6 40", I'm not sure it is the TV but back when I first got it I couldn't get a tuned signal due to digital errors, guess I know what the likely cause was now.

Modern laptops are supposed to be properly designed, including "correctly grounded" PSU's.

Unfortunately, solving this when both 1) the laptop/PSU isn't adequate, and 2) you're using HDMI connectivity, is rather expensive. Basically, you need to kill the electrical connectivity over the HDMI, meaning you need an optical link, like this. For more information, see Fibre Extenders - HDMI Fibre Extenders and Distribution.

The cheapest solution is to use a "dirty" laptop off batteries for this application.
Thanks those were the sort of things I was looking at, I did try a 5GHz HDMI video sender which cured my audio problem but didn't work very well, poor resolution and dropping frames constantly, I had to take it back.

Alternatively I'm looking an isolating transformer (mains not an audio/phono one)
Something like this.
Buy Safety Site Transformers 1phase isolation transformer,750VA 110V Carroll & Meynell CM15002 online from RS for next day delivery.

To add to this issue, my Exposure XXI (21) pre-amp seems to be far more susceptible to this over other equipment, suffice to say I'd replace the laptop before the Exposure (neither is really an option though).
 

Mark.Yudkin

Distinguished Member
Thanks those were the sort of things I was looking at, I did try a 5GHz HDMI video sender which cured my audio problem but didn't work very well, poor resolution and dropping frames constantly, I had to take it back.
Which is why I didn't suggest using such a solution, but instead suggested a properly manufactured fibre extender.

Alternatively I'm looking an isolating transformer (mains not an audio/phono one)
Whether such a device will work will depend on how it's been designed. If it's been properly designed to satisfy safety requirements, it will not break the earth and hence cannot solve your problem. An audio isolating transformer also won't work, as your loop is over HDMI.

What happened when you tried a different, better, PSU?
 

pragmatic

Distinguished Member
I have two PSUs for the laptop hence why I'm not immediately following that route up as there is no guarantee it will fix it (Both are official out of the box Sony PSUs).
I don't know what would constitute a better PSU than the manufacturers?

An Audio isolator should work as the only interaction between my preamp and the rest of the system is via a single pair of Phono connections (at least right now). I'd rather fix the power end or the HMDI side of it than stick something in the audio signal path.
 

Mark.Yudkin

Distinguished Member
I have two PSUs for the laptop hence why I'm not immediately following that route up as there is no guarantee it will fix it (Both are official out of the box Sony PSUs).
I don't know what would constitute a better PSU than the manufacturers?

An Audio isolator should work as the only interaction between my preamp and the rest of the system is via a single pair of Phono connections (at least right now). I'd rather fix the power end or the HMDI side of it than stick something in the audio signal path.
I asked about the PSU as you said in post #3 that you were trying it, but you never got back on the result. The replacement PSU should be high-impedance grounded, and as larkone explained, modern laptop PSUs are supposed to be designed that way. Older PSU's tended not to be, so it's not a case of "the manufacturer's is the best" but whether it's a recent unit or an older, noisier design.

Normally the loop goes through a complex path involving the HDMI cable and multiple devices, which is why it's such a pain in the butt to resolve. But you can test if the phono connections are the only problem simply by removing them. If the hum goes, insert a simple stereo transformer.
 

pragmatic

Distinguished Member
Thanks Mark, as I said in the OP
me said:
Laptop docked -> TV -> Oppo/DVD player -> Pre-amp -> Power amps -> Speakers

Removing any of these links removes the noise.
Although what I should have said

1a) Mains/UPS -> Laptop docked -> TV
1b) TV -> Oppo/DVD player -> Pre-amp
2) CD Player -> Pre-amp
3) SqueezeBox -> Pre-amp

4) Pre-amp -> Power amps -> Speakers

Disconnecting anything in 1 a or b removes the noise. I also 'cure' the sound if I run the laptop off its internal battery or the UPS battery (UPS is disconnected from mains). I get the noise regardless if the TV and Oppo are turned on/pugged into mains, as long as there is a cable connection linking the mains powered laptop (via hdmi it seems) to the pre-amp somehow.

The noise is heard through the speakers regardless of the pre-amp input selected, e.g. change input to CD player and the sound is still there.
The volume of the noise is also independent of the current volume of the pre-amp.

At the moment I remove the phono cables between the Oppo and pre-amp when I'm not using the oppo as its the easiest thing to do.
I turn the laptop off when I want to use the oppo with my hifi (via preamp).

I think its safe to conclude the HDMI out when plugged into the mains seems to be the root of the problem.

The PSU is obviously an issue, but without buying a bus load of them is there any way discover a 'good one'?

The sound is more a whine than a hiss and does not sound too dissimilar to computer speakers connected to an old PC motherboard sound card and moving say the mouse makes a noise heard through the speakers (digital interference?). The sound is both variable (is not a constant hum but rather comes and goes for different lengths every second or so) and relentless but independent of what is actually happening on the laptop (i.e. if I just leave it switched on without interacting with it on an empty desktop).

The laptop is a 2010 Sony Vaio Z (Z12), manufactured in Japan, I'm using the supplied sony PSUs, for either the Dock or the laptop. Both of these cause the exact same issue, regardless if the laptop is plugged into the dock or not. The problem has existed since day one, but with my old 'all in one DVD system' it wasn't anywhere near as loud, so simply lived with it.

Maybe I just got unlucky with the PSUs and buy a few from ebay/Maplin?
 
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pragmatic

Distinguished Member
Additionally I have 3 ferrite rings I have tightly wound the DC output of the PSU around, this reduced the noise volume by about half but it is still there, I tried a similar thing with the HDMI cable but there was no apparent difference.
 

Mark.Yudkin

Distinguished Member
So far I've been working on a constant hum / hiss as per the title rather than an intermittent, variable whine. Chances are that you can't fix such a whine with a new PSU (that's designed to address the 50Hz hum) or measures such as ferrite rings (they're against RF frequency noise).

My last suggestion from post #5 remains the cheapest: you've already said it works.

A fibre extender is the only viable solution for HDMI-induced loops when can't just run off batteries and need fully flexible interconnectivity.

At the moment though, it appears the loop is between the PC, the TV+Oppo and the pre-amp + power amp, etc. If that is the case, and you do not add any other (grounded) devices that alter this, then inserting a decent stereo audio-transformer-based isolator such as the Behringer MICROHD HD400 (or a simple sub-£5 equivalent) between the TV/Oppo combo and the pre-amp will likely break the loop by galvanically partitioning the setup into:
1) TV, Oppo, laptop
2) CD, Squeezebox, pre-amp, power amp
 

pragmatic

Distinguished Member
Thanks thats my thinking right now.

I can most likely solve the problem at the point of input into the pre-amp.
I'd like to remove the noise at the power level so as not to potentialy effect other things, like for example ethernet over power and my tv's ability to get a reception from an external aerial (I get a huge amount of 'errors' when tuning the tv).

I have one more thing to try before buying something like the Behringer, which seems pretty cheap at the power side (without buying an isolating transformer).

I've also looked at an older device by Marantz/Philips which seems to have been invented for this very problem I'm having, but they were only made in the 90's and difficult to get hold of.
 

Mark.Yudkin

Distinguished Member
I would not be surprised if your TV errors were related to the noisy laptop, perhaps you should test that?

Audio isolators come in all sorts of prices and qualities. The Behringer audio isolator seems to me to offer a decent return on investment. The sub-£5 units offer a simple solution for lesser demands. A Jensen CI-2RR is an audio isolator for the more demanding consumer (and they publish a comprehensive datasheet).

Which Marantz / Philips device?
 

Mark.Yudkin

Distinguished Member
Marantz DLT-1
"The Marantz DLT-1 helped to filter out RF mush coming out of many CD players twenty years ago."

I had not considered your problem as "RF mush coming out of your Oppo", although your statement "I've also looked at an older device by Marantz/Philips which seems to have been invented for this very problem I'm having" implies that you are convinced otherwise.

Since I've obviously totally misunderstood your problem and am equally obviously unable to provide any assistance, I'll drop out. Sorry.
 
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pragmatic

Distinguished Member
No Problem Mark, thanks for your help.

I'll post up the noise as an mp3 or a video, I say the Marantz not because the RF is originating from the OPPO, but the laptop, but as the OPPO is the conduit that the noise comes through its much of muchness.

When I actually solve this I'll post up my solutions.
 

larkone

Member
Did a bit more digging and this does seem to be an issue with Sony laptops. Some people have managed to cure the problem by upgrading the BIOS and the sound drivers. No guarantee it will solve your problem but a cheap way forward that will at least eliminate two potential causes of the noise on a Sony Laptop.
 

pragmatic

Distinguished Member
Wow thanks I'll give that a go tonight, worth a go (would be surprised if it fixed it, but you never know).
 

Thooms

Active Member
Check the Mic and Line inputs are muted too...
 

pragmatic

Distinguished Member
Got it fixed, the Marantz DLT-1 completely removed the audio noise, now I only have the faint noise floor of the pre-amp (i.e ear against the speaker at high volume with nothing playing).

I still have electrical noise (non audio related) as I've done nothing to fix this. I'll try an isolating transformer for the laptop power supply, I'd like to see if this would remove the audio noise too.

My setup changed slightly as I included a DAC (Nad M51) connected via HDMI.

1a) Mains/UPS -> Laptop docked(DVI-D) -> (HDMI)TV
1b) Oppo/DVD player -> (HDMI.1) TV
1c) Oppo/DVD player -> (HDMI.2) DAC

2) SqueezeBox -> (Optical)DAC

3) CD Player (Phono) -> Pre-amp

4a) DAC (HDMI.passThrough) -> Projector
4b) DAC (Phono.out) -> Pre-amp-> Power amps -> Speakers

(pretty complicated for a 2.1 system!)

The DAC added what I assume is a ground loop when connected to OPPO via HDMI (regardless if the TV was also connected to the OPPO).

The Marantz removed this noise too.
 
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pragmatic

Distinguished Member
I tried the other suggestions, for muting the mic and updating the firmware, unfortunately no luck for me.
 

pragmatic

Distinguished Member

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