Presentation Problems

[Big Kev]

Occasionally when demonstrating PTE at clubs and seminars one of two problems have been known to occasionally occur:

- lines appear on the projected picture when an animation is taking place but these do not show on the laptop screen.

- the sound track is affected by the addition of noise generated by the computer circuits.

Either of these faults can be immediately cured by running the laptop on the battery and so the switched mode power supply is the suspect.

Has anyone else encountered this problem and more importantly have you discovered a cure!!!

John

[Conflow]

Occasionally when demonstrating PTE at clubs and seminars one of two problems have been known to occasionally occur:

- lines appear on the projected picture when an animation is taking place but these do not show on the laptop screen.

- the sound track is affected by the addition of noise generated by the computer circuits.

Either of these faults can be immediately cured by running the laptop on the battery and so the switched mode power supply is the suspect.

Has anyone else encountered this problem and more importantly have you discovered a cure!!!

John

John,

Yes these problems can occur on various Laptops this depending on the Make & Model No: and age of the Laptop.

The Audio noise is common to all Laptops where the audio-signals are taken from the Headphone-Output and where

the 'Recorded-Audio' levels were too low in the 1st.instance. Proper recording levels are between 90~96db and

anything lower that 60db will result in noisy reproduction as the noise-recording becomes an integral part of the

Soundtrack, whereafter heavy amplification to bring up the levels also brings up the noise.Then again other Laptops

are generically 'noisy' and there is nothing you can do about it except extract the Audio in digital-format from a

HDMI-socket into peripheral equpment for replaying. (There are other methode depending on the particular Laptop).

Concerning the 'Video-lines' on the Projector-Screen but not on the Laptop is usually a problem of 'older' Projectors

not having enough 'spooling-memory' to pre-process your Show before projection. Much 'older' Projectors use 'real-time'

projection and can not resolve 'movement' within an Image. Put bluntly if the Projector can show a DVD then it will also

render your Slideshow. There are other possible causes of this ~ it could be Mains-noise or extraneous pick-up etc; ???

Hope this helps...

Brian.(Conflow)

[jkb]

Another problem I sometimes get on my laptop, which is the same as John's - Acer 5920G with nvidia 8600M GS graphics card - is that if the laptop goes to sleep, during tea break etc. Then the first time I play a sequence after waking it up again, a black band moves down the projected image. The image on the laptop screen is unaffected. It is as though the projector is on a different refresh rate to the laptop. Laptop is 60hertz refresh.

If I escape out of the sequence & restart it everything is fine. Again this only happens on certain projectors, one of which is less than 2 years old. Don't know the make offhand.

This problem occurs both on mains or battery power.

Jill

[Conflow]

Jill,

This should sort out your problem ~ See "Attachment".

Brian.(Conflow)

[jkb]

Hi Brian,

All this will do is stop the laptop going to sleep. It does not explain the black bar showing on the projected image?

I ususally run on a separate user when giving shows & I thought I had that setup to not sleep, maybe not, will have to check.

Jill

[Big Kev]

John,

Yes these problems can occur on various Laptops this depending on the Make & Model No: and age of the Laptop.

The Audio noise is common to all Laptops where the audio-signals are taken from the Headphone-Output and where

the 'Recorded-Audio' levels were too low in the 1st.instance. Proper recording levels are between 90~96db and

anything lower that 60db will result in noisy reproduction as the noise-recording becomes an integral part of the

Soundtrack, whereafter heavy amplification to bring up the levels also brings up the noise.Then again other Laptops

are generically 'noisy' and there is nothing you can do about it except extract the Audio in digital-format from a

HDMI-socket into peripheral equpment for replaying. (There are other methode depending on the particular Laptop).

Concerning the 'Video-lines' on the Projector-Screen but not on the Laptop is usually a problem of 'older' Projectors

not having enough 'spooling-memory' to pre-process your Show before projection. Much 'older' Projectors use 'real-time'

projection and can not resolve 'movement' within an Image. Put bluntly if the Projector can show a DVD then it will also

render your Slideshow. There are other possible causes of this ~ it could be Mains-noise or extraneous pick-up etc; ???

Hope this helps...

Brian.(Conflow)

Hi Brian,

Thanks for the suggestions although the sound fault is nothing to do with the 'signal to noise ratio' of the recordings.

The noise comes from the circuits within the computer and is not dependent on the volume. Similar problems can be caused by 'earth loops' and at first I thought it was that however when this fault occurred whilst doing a demonstration at Wrexham, I removed the earth braid and the fault remained - although the sound remained fine!!!

The problem seems to occur more with the Canon range of projectors. I wondered at first if it was due to the projector resizing the images...but again switching over to battery power sorted the problem out hence my suspicion of the laptop switched mode power supply.

Best wishes,

John

[Lmoreels]

Hy,

I always use this to eliminate noise: http://www.behringer.com/EN/Products/UCA202.aspx.

a Ultra-Low Latency 2 In/2 Out USB/Audio Interface with Digital Output.

There are other brands to.

Luc M

[fh1805]

John,

On the subject of noise pickup, you might find the link below of interest. It's from the Audacity forum. I've linked to my posting of my findings but you probably should read the whole topic to get that into its proper context.

http://forum.audacityteam.org/viewtopic.php?f=16&t=63439&start=10#p169890

regards,

Peter

[jkb]

Hi Peter,

Thanks for the Link. However the problem is not concerned with residual noise. It is directly linked to the power supply.

Even if no sound is playing you can still hear a hum through the speakers. Note this only applies to some powered speakers.

When using an amplifier & normal speakers the sound is clear & there is no hum.

Unplugging the power supply & running the laptop on batteries also removes the hum.

Jill