| Author |
Message |
laura fairhead
Guest
|
 Posted:
Mon Sep 19, 2005 8:57 pm Post subject:
Q regarding television noise |
|
|
Hi ppl,
I have a quick question which is possibly not totally on-topic
but is related to television at least.... I am not an electrician
but have some knowledge of the basics and recently find myself
wondering about a phenomenon which I've noticed for a long time
now dealing with computer CRT's and television sets, namely
that they emit a very high pitched tone (possibly 15-20 khz)
when operating. I am wondering where this sound comes from
and how it is generated. The only thing I can observe is that
mains transformers emit a low pitched hum which must originate
from the low frequency AC oscillation and so I would suspect
the sound from the tv set was coming from the coil at the
rear of the CRT. Am I correct about that? If so, how is the
sound created? What is moving the air? Be very grateful for any
pointers...!
bestwishesfrom
laura
--
echo alru_aafriehdab@ittnreen.tocm |sed 's/\(.\)\(.\)/\2\1/g' |
|
| Back to top |
|
 |
Jan Panteltje
Guest
|
| Posted:
Tue Sep 20, 2005 12:08 am Post subject:
Re: Q regarding television noise |
|
|
On a sunny day (Mon, 19 Sep 2005 20:57:07 +0000 (UTC)) it happened
run_signature_script_for_my_email@INVALID.com (laura fairhead) wrote in
<432f2539.5042825@news.btinternet.com>:
| Quote: |
Hi ppl,
I have a quick question which is possibly not totally on-topic
but is related to television at least.... I am not an electrician
but have some knowledge of the basics and recently find myself
wondering about a phenomenon which I've noticed for a long time
now dealing with computer CRT's and television sets, namely
that they emit a very high pitched tone (possibly 15-20 khz)
when operating. I am wondering where this sound comes from
and how it is generated. The only thing I can observe is that
mains transformers emit a low pitched hum which must originate
from the low frequency AC oscillation and so I would suspect
the sound from the tv set was coming from the coil at the
rear of the CRT. Am I correct about that?
Correct, the (it is called deflection coils) use strong magnetic fields and |
may vibrate.
More noise comes usually from the horizontal output transformer, that
is the transformer driving those coils (and associated inductors).
The core (a comprssed iron powder) consists of 2 pieces that will sometimes
strongly vibrate under influence of the magnetic field.
The 15625 Hz you hear is the horizontal scanning frequency, the little
spot that draws the picture on the TV moves 15625 times from left to right,
under influence of the magnetic fields of those deflection coils.
(And 50 times per second from top to bottom, there is also a 50 Hz noise).
When we go HDTV on CRT or when you have a 100Hz TV the H frequency is higher
and above what we can hear.
I have heard stories of singing birds dying when people bought a (normal) TV
because they could not stand those high pitches.
For us 15 to 20 kHz is at the edge of what most people can hear.
LCD TVs should not have this problem, but may still use some converter that
makes noise...
LCD TVs do not have a very good picture IMO, so I would not want to swap.
_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 140,000 groups
Unlimited download
http://www.usenetzone.com to open account |
|
| Back to top |
|
|
Java Jive
Guest
|
| Posted:
Tue Sep 20, 2005 12:08 am Post subject:
Re: Q regarding television noise |
|
|
"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:432f2e89@news.usenetzone.com...
| Quote: |
For us 15 to 20 kHz is at the edge of what most people can hear.
|
Yes, but it varies with age. Young people can hear frequencies up to 25KHz
absolute maximum, but that upper limit decreases with age. A group of us
tested our upper limit in the physics lab when I was in my late teens, my
upper limit was about 23KHz and the group average was above 20KHz. Just a
few years later in my early 20s, mine was already down to around 17KHz.
| Quote: | LCD TVs do not have a very good picture IMO, so I would not want to swap.
|
IMO LCDs have a superior picture to CRTs. |
|
| Back to top |
|
|
Walt Davidson
Guest
|
| Posted:
Tue Sep 20, 2005 12:08 am Post subject:
Re: Q regarding television noise |
|
|
On Mon, 19 Sep 2005 22:53:29 +0100, "Java Jive" <java@evij.com> wrote:
| Quote: | IMO LCDs have a superior picture to CRTs.
|
IMO they do not. Neither do TFTs.
--
Walt Davidson Email: g3nyy @despammed.com |
|
| Back to top |
|
|
Zak
Guest
|
| Posted:
Tue Sep 20, 2005 8:08 am Post subject:
Re: Q regarding television noise |
|
|
Java Jive wrote:
| Quote: | IMO LCDs have a superior picture to CRTs.
|
They do for computer use, where a pixel is a pixel.
Fot TV use, there seems to be a problem that the screens overprocess the
video, with all kinds of weird, unwanted and sometimes downright ugly
behaviour:
- video is delayed by processing. The audio path is separate and not
delayed: bye bye lip sync. Some screens manage to make the delay
slightly variable, it seems.
- video is sharpened and de-noised to such extents that the image looks
like a caricature painting. Nice first impression but a lot of details
are actually gone.
- video resolution and screen resolution do not match. The resizing
results in loss of quality.
- video is interlaced; screens are not. The screen must figure out what
the moving objects are and try to assemble the missing information in
the other half screen from those estimates. Imperfections lead to
scrolling text looking jaggy, jumping around, being distorted...
If the input video does not need processing - for example, it comes from
a VGA card - LCDs are fine. The processing (designed to look good the
first second, not the rest of the life of the screen) is what makes them
bad.
Thomas |
|
| Back to top |
|
|
R. Mark Clayton
Guest
|
| Posted:
Tue Sep 20, 2005 9:30 am Post subject:
Re: Q regarding television noise |
|
|
"Java Jive" <java@evij.com> wrote in message
news:432f5b61@news.greennet.net...
| Quote: | "Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:432f2e89@news.usenetzone.com...
For us 15 to 20 kHz is at the edge of what most people can hear.
Yes, but it varies with age. Young people can hear frequencies up to
25KHz
absolute maximum, but that upper limit decreases with age. A group of us
tested our upper limit in the physics lab when I was in my late teens, my
upper limit was about 23KHz and the group average was above 20KHz. Just a
few years later in my early 20s, mine was already down to around 17KHz.
LCD TVs do not have a very good picture IMO, so I would not want to swap.
IMO LCDs have a superior picture to CRTs.
|
Yes they do by quite some margin IME, however for plasma screens many are
poorer due to low US style resolution of 852x480 (UK PAL has at least 576
displayed lines). |
|
| Back to top |
|
|
Nigel Goodwin
Guest
|
| Posted:
Tue Sep 20, 2005 2:15 pm Post subject:
Re: Q regarding television noise |
|
|
In message <432fa67c$0$12429$756600cd@cachenews.cambrium.nl>, Zak
<jute@zak.invalid> writes
| Quote: | - video resolution and screen resolution do not match. The resizing
results in loss of quality.
|
This appears to be the main source of the problem, try setting your
laptop to a lower resolution and see how crap the picture is!.
Whereas a CRT is completely analogue, so reducing the picture resolution
still gives you that amount of resolution, an LCD (or plasma) doesn't
work like that - so reducing the picture resolution looks crap because
you don't have an even number of pixels on the screen for the number of
pixels in the picture.
We've recently got a Euro 1080 demo box at work, and connected to a HDMI
LCD TV the picture is absolutely superb - NOT so much because of the
higher resolution (which is nice!), but because the resolution of the
screen and picture now match - it overcomes pretty well all the defects
of an LCD or plasma screen.
--
Nigel.
/------------------------------------------------------------\
| Nigel Goodwin | E-Mail : nigelg@lpilsley.co.uk |
| Lower Pilsley | Website : http://www.lpilsley.co.uk |
| Chesterfield | Author of WinPicProg |
| England | http://www.winpicprog.co.uk |
\------------------------------------------------------------/ |
|
| Back to top |
|
|
Java Jive
Guest
|
| Posted:
Tue Sep 20, 2005 3:12 pm Post subject:
Re: Q regarding television noise |
|
|
"Zak" <jute@zak.invalid> wrote in message
news:432fa67c$0$12429$756600cd@cachenews.cambrium.nl...
CRT diehards try to invent something new every time this subject comes up
(yawn) ...
LCDs have the advantages of
+ An absolutely flat undistorted picture
+ Minimal on-screen reflections
+ More reliable colour balance, though I wonder if that's just because,
being more expensive, manufacturer's feel obliged to take more care over
their factory adjustments, and that once they become the norm, in big shops
we may start to see lines of LCDs of the same make with wildy different
colour balances, as we already do with CRTs.
+ Significantly reduced power consumption.
+ Total absence of X-radiation
+ Reduced bulk and weight.
Some claim they have the disadvantage of reduced contrast ratio, which is
the only anti-LCD claim I have ever been able to verify, but ...
- It's slight compared with a CRT scene for scene.
- Neither technology has adequate contrast ratio, both need adjustment
between dark and light scenes, and once you have to make any adjustment at
all, a slight increase in one adjustment over the other is neither here nor
there.
.... so although this claim does at least have some truth, I find it
insignificant in practice.
My advice for anyone buying TVs always is: Take some DVDs (*1) around the
stores and ask to see them played on the most promising sets. This will
give direct comparisons both between those in the shop and with the current
set at home, then make a decision on what the eyes (and the wallet) say.
*1 Hire some if necessary - I suggest a good mix of 3 - 5 including at
least:
1) To check colour balance, one natural history and one sitcom or reality
show (for human flesh tones indoors);
2) For interlacing and movement, some action shots such as the latest
blockbuster that takes the fancy, and some *interlaced* sport action.
3) Any thing else commonly watched at home.
4) As this seems to come up with some makes of LCDs,
something containing dimly lit scenes for judging contrast ratio, say
"Stephen Hawking's Universe" or the opening of "All The President's Men".
Also turn the set onto BBC News 24 or Sky News for how it shows poor quality
material. For example, Sky football clips are often visibly over-compressed
when shown on BBC News 24 - this may actually show up more clearly on a
good set such as an LCD, and, although it's strictly the fault of the
delivery system, which will hopefully one day improve as HDTV comes in,
rather than the TV's, this may constitute a valid reason not buy a more
expensive set until delivery systems themselves have been upgraded.
TVs can only display as good as what the delivery system feeds them. If you
buy a better quality TV such as an LCD, then any deficiencies in your
delivery system will naturally become more obvious. When upgrading one item
in a delivery chain you usually have to upgrade them all. You wouldn't buy
a Rolls Royce and try to run it on chip fat, would you?
| Quote: | - video is delayed by processing. The audio path is separate and not
delayed: bye bye lip sync. Some screens manage to make the delay
slightly variable, it seems.
|
This has nothing to do with LCDs vs CRTs - you couldn't sell a single LCD
if they all had a fault as basic and obvious as that.
If you are experiencing this, either you have/had a set with a very strange
fault and you should (have) take(n) it back, or much more likely it's a
product of the delivery system - many CRTs are quite old and we were used
to watching them in analogue systems, where interference just caused
unwanted noise, whereas most people who have bought an LCD have also bought
a digital delivery system, where interference can cause lipsync problems.
| Quote: | - video is sharpened and de-noised to such extents that the image looks
like a caricature painting. Nice first impression but a lot of details
are actually gone.
|
Again, loss of image detail is a characteristic of an over-compressed
digital delivery system. Most UK Freeview is over compressed, UK Freesat
seems a bit better, DVD is better still , though even some DVDs have
compression artifacts on some scenes.
| Quote: | - video resolution and screen resolution do not match. The resizing
results in loss of quality.
- video is interlaced; screens are not. The screen must figure out what
the moving objects are and try to assemble the missing information in
the other half screen from those estimates. Imperfections lead to
scrolling text looking jaggy, jumping around, being distorted...
|
Again, video resolution and interlacing are problems with the delivery
system - mosts DVDs have higher resolution than broadcast TV, and are
progressive, not interlaced. You seem to be suggesting that TV
manufacturers should deliberately cripple their TVs to show the worst
possible source to best effect, but forget about the superior quality
sources already available and those that will be broadcast in the future.
This would be illogical and very bad business practice.
| Quote: | If the input video does not need processing - for example, it comes from
a VGA card - LCDs are fine. The processing (designed to look good the
first second, not the rest of the life of the screen) is what makes them
bad.
|
Here it sounds like you're trying to judge LCD TVs by looking at video on a
PC LCD monitor. You can't make such a comparison. Although they happen to
share the same underlying technology, the design criteria are different and
so are the results. I could equally well argue that all CRTs are crap
because of the terrible quality of the display on old cash machines, and I'd
be just as mistaken. |
|
| Back to top |
|
|
Jan Panteltje
Guest
|
| Posted:
Tue Sep 20, 2005 4:08 pm Post subject:
Re: Q regarding television noise |
|
|
On a sunny day (Tue, 20 Sep 2005 11:12:42 +0100) it happened "Java Jive"
<java@evij.com> wrote in <43300838@news.greennet.net>:
| Quote: | "Zak" <jute@zak.invalid> wrote in message
news:432fa67c$0$12429$756600cd@cachenews.cambrium.nl...
CRT diehards try to invent something new every time this subject comes up
(yawn) ...
I am not a CRT diehard (I think). |
Thats said, here are some contras of LCD:
Let's assume a set lifetime of at least 7 years (normal for CRT).
1) How many defective pixels and where will there be in your LCD (after 7
years), remember ONE defective pixel is like flee poop (if black) on the
middle of your screen, or if white even worse.
2) How long does your (if any) backlight last, and how much does it cost to
replace.
3) The gamma on ALL the LCDs I have seen in the shops suck, a CRT has
gamma 1/y^(2.2) by nature.
In case of LCD this is achieved electronically, and is it correct?
4) The resizing needed as already mentioned for different resolutions.
5) The black level of a good CRT beats LCD.
6) The power consumption story is not really that true, look at the watts
used.
In my view LCD (TFT) is a transient.
I am much more interested in the new micro electron gun emitter displays
that have normal CRT phosphors, low power, emit light, and are the perfect
CRT replacement.
These are already coming on the market now.
Plasma has burn in.
| Quote: | LCDs have the advantages of
LCD will work fine reflective in bright sunlight. |
As it seems 90% of the people do NOT know how to adjust brightness, contrast,
and saturation, and 10% of the manufacturers do not even know you have to
clamp black level in video (I have seen Eastern sets with AC coupling), I
think for THOSE (people) they will never see the difference anyways, except
in their purse weight (it will be lighter after buying latest tech).
If these people then use that (latest tech) to watch crap low bandwidth payed
channels like RTL9 (and RTL9 has less then VHS quality it seems), then who
cares.
So then they must have bought it (flat screen) to save room space ;-)
So the question then to ask is: 'What did you use the freed room space for?'.
If that space was rented out, did it pay for the difference in price between
LCD and CRT?
Well OK.
_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 140,000 groups
Unlimited download
http://www.usenetzone.com to open account |
|
| Back to top |
|
|
R. Mark Clayton
Guest
|
| Posted:
Tue Sep 20, 2005 5:24 pm Post subject:
Re: Q regarding television noise |
|
|
----- Original Message -----
From: "Java Jive" <java@evij.com>
Newsgroups: alt.satellite.tv.europe
Sent: Tuesday, September 20, 2005 11:12 AM
Subject: Re: Q regarding television noise
| Quote: | "Zak" <jute@zak.invalid> wrote in message
news:432fa67c$0$12429$756600cd@cachenews.cambrium.nl...
CRT diehards try to invent something new every time this subject comes up
(yawn) ...
LCDs have the advantages of
+ An absolutely flat undistorted picture
+ Minimal on-screen reflections
+ More reliable colour balance, though I wonder if that's just because,
being more expensive, manufacturer's feel obliged to take more care over
their factory adjustments, and that once they become the norm, in big
shops
we may start to see lines of LCDs of the same make with wildy different
colour balances, as we already do with CRTs.
+ Significantly reduced power consumption.
+ Total absence of X-radiation
+ Reduced bulk and weight.
|
All true, although CRT's retain some advantages: -
- highly reliable at macro and micro level (no on or off pixels)
- long term colour stability (although a tendency to burn in)
- better viewing angle
- higher emissivity (brighter)
etc.
OTOH LCD is definitely the way forward, and I am waiting for the price to
fall. Currently a higher resolution 42" LCD screen is ££££, whereas CRT
price's have fallen dramatically. |
|
| Back to top |
|
|
R. Mark Clayton
Guest
|
| Posted:
Tue Sep 20, 2005 9:31 pm Post subject:
Re: Q regarding television noise |
|
|
"Java Jive" <java@evij.com> wrote in message
news:43307fa2$1@news.greennet.net...
| Quote: | "R. Mark Clayton" <nospamclayton@btinternet.com> wrote in message
All true, although CRT's retain some advantages: -
- long term colour stability
How can you in one sentence accept the entire truth of what I said, but
then
in the next contradict it? Anyhow, to stick to the point ...
Take a look at the differing colour balances on CRTs when you're next in a
store, they don't exactly suggest long term stability, do they?
|
Colour balance on decent CRT's is excellent, what I was talking about was
the long term, where different LED compositions may age at different rates
(especially blue). |
|
| Back to top |
|
|
Java Jive
Guest
|
| Posted:
Tue Sep 20, 2005 10:08 pm Post subject:
Re: Q regarding television noise |
|
|
"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:4330073e@news.usenetzone.com...
| Quote: | On a sunny day (Tue, 20 Sep 2005 11:12:42 +0100) it happened "Java Jive"
java@evij.com> wrote in <43300838@news.greennet.net>:
"Zak" <jute@zak.invalid> wrote in message
news:432fa67c$0$12429$756600cd@cachenews.cambrium.nl...
CRT diehards try to invent something new every time this subject comes up
(yawn) ...
I am not a CRT diehard (I think).
|
Ok, let's see ...
| Quote: | Thats said, here are some contras of LCD:
Let's assume a set lifetime of at least 7 years (normal for CRT).
1) How many defective pixels and where will there be in your LCD (after 7
years), remember ONE defective pixel is like flee poop (if black) on
the
middle of your screen, or if white even worse.
|
If you see dead pixels in the shop, you don't buy that one in the same way
you don't buy a CRT with a scratched screen. I've had both of my LCDs for
half that time, there are and have been no dead pixels.
If you are not a CRT diehard, you should apply similar reasoning to CRTs. I
note that you don't, so I will: Assuming they are fortunate enough to be so
in the beginning, a rare thing in itself, how many CRTs will still be in
perfect adjustment after seven years?
| Quote: | 2) How long does your (if any) backlight last, and how much does it cost
to
replace.
|
Both still going. How long will your tube last?
| Quote: | 3) The gamma on ALL the LCDs I have seen in the shops suck, a CRT has
gamma 1/y^(2.2) by nature.
In case of LCD this is achieved electronically, and is it correct?
|
I've worked in the photographic trade on prints and enlargements, so have at
least a reasonable eye, and both my LCDs give better colour balance than any
CRT I can recall seeing, let alone have actually owned.
| Quote: | 4) The resizing needed as already mentioned for different resolutions.
|
I think this is a theoretical argument that is a myth in practice - I've
*never* noticed a problem with this on my LCDs. Anyway as already
explained, it's a delivery system issue.
| Quote: | 5) The black level of a good CRT beats LCD.
|
As already explained, the contrast ratio of both is inadequate to cope with
dark scenes followed by light scenes with no intervening adjustment - for
optimum viewing of dark scenes with CRTs you have to reduce the brightness
to avoid picture noise, with LCDs you have to reduce the backlight level.
| Quote: | 6) The power consumption story is not really that true, look at the watts
used.
|
I did ... LCD: Use 49W Standby 4W - *smaller* CRT: Use 52W, no standby
figure given, I suspect it's higher than 4W.
| Quote: | In my view LCD (TFT) is a transient.
I am much more interested in the new micro electron gun emitter displays
that have normal CRT phosphors, low power, emit light, and are the perfect
CRT replacement.
These are already coming on the market now.
|
I agree these developments are interesting ...
| Quote: | As it seems 90% of the people do NOT know how to adjust brightness,
contrast,
and saturation, and 10% of the manufacturers do not even know you have to
clamp black level in video [snip]
|
LCDs seem to be less variable than CRTs. It's common to go into a large
shop and see lines of CRTs by the same manufacturer, sometimes even the same
models, with very different pictures, particularly wrt colour balance. It's
a plus for LCDs that they don't seem to show such variability and their
colour balance is usually good without requiring any adjustment.
That said, there are bad LCDs and good CRTs. As with all things,
prospective purchasers should always research purchases before parting with
money, and should compare the pictures from a variety of the most promising
sets, and then make their own decision. |
|
| Back to top |
|
|
Ranulf Doswell
Guest
|
| Posted:
Tue Sep 20, 2005 10:49 pm Post subject:
Re: Q regarding television noise |
|
|
In article <dgpgl1$kep$1@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com>,
R. Mark Clayton <nospamclayton@btinternet.com> wrote:
| Quote: |
----- Original Message -----
From: "Java Jive" <java@evij.com
Newsgroups: alt.satellite.tv.europe
Sent: Tuesday, September 20, 2005 11:12 AM
Subject: Re: Q regarding television noise
"Zak" <jute@zak.invalid> wrote in message
news:432fa67c$0$12429$756600cd@cachenews.cambrium.nl...
CRT diehards try to invent something new every time this subject comes up
(yawn) ...
All true, although CRT's retain some advantages: -
- highly reliable at macro and micro level (no on or off pixels)
|
I'd dispute that. I have a CRT monitor at work that has 3 dead pixels.
No doubt it's dust which has somehow got trapped in between the wires
making up the Trinitron "grille", but nonetheless, it has the same
effect. These weren't from point of manufacture, either, I noticed one
shortly after obtaining the monitor, and the other two appeared some
months later. It's a cheap Compaq monitor though, so I'm not surprised
the quality is rubbish.
| Quote: | - long term colour stability (although a tendency to burn in)
|
Also, long term convergence issues.
| Quote: | - better viewing angle
- higher emissivity (brighter)
|
Granted, although modern LCDs seem to do a fantastic job on this front
too.
| Quote: | OTOH LCD is definitely the way forward, and I am waiting for the price to
fall. Currently a higher resolution 42" LCD screen is ££££, whereas CRT
price's have fallen dramatically.
|
Likewise, I still don't actually own an LCD. If it wasn't for the fact
that I bought a top-of-the-range Sony monitor at home some years back,
costing double what an equivalent sized LCD would cost now, I'd be off
like a shot to buy one. Trouble is, even though my monitor has slight
convergence problems in one corner, I can't justify replacing it.
And I'll add that I've never seen a CRT that I'm actually happy with,
i.e. at the highest resolutions that they claim to support, they're
generally blurry. They're almost impossible to get a perfectly square
image and I've generally learnt to live with that. Every CRT I've ever
owned has some degree of convergence problems, particularly older ones,
whereas almost every laptop screen I see nowadays looks fantastic by
comparison - high res and every pixel easily discernable.
Ralf.
--
Ranulf Doswell | Please note this e-mail address
www.ranulf.net | expires one month after posting. |
|
| Back to top |
|
|
Java Jive
Guest
|
| Posted:
Tue Sep 20, 2005 11:39 pm Post subject:
Re: Q regarding television noise |
|
|
"R. Mark Clayton" <nospamclayton@btinternet.com> wrote in message
news:dgpgl1$kep$1@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com...
| Quote: |
----- Original Message -----
From: "Java Jive" <java@evij.com
Newsgroups: alt.satellite.tv.europe
Sent: Tuesday, September 20, 2005 11:12 AM
Subject: Re: Q regarding television noise
"Zak" <jute@zak.invalid> wrote in message
news:432fa67c$0$12429$756600cd@cachenews.cambrium.nl...
|
My mistake with the quoting - he didn't, I did ...
| Quote: | + More reliable colour balance [snip]
All true, although CRT's retain some advantages: -
- long term colour stability
|
How can you in one sentence accept the entire truth of what I said, but then
in the next contradict it? Anyhow, to stick to the point ...
Take a look at the differing colour balances on CRTs when you're next in a
store, they don't exactly suggest long term stability, do they?
| Quote: | (although a tendency to burn in)
|
Yes, an increasing problem with the DOGs (logos) on modern digital channels.
| Quote: | - highly reliable at macro and micro level (no on or off pixels)
|
Like I said, you just don't buy one that shows a fault, just the same way as
you don't buy a faulty CRT.
| Quote: | - better viewing angle
|
My LCDs are comparable with CRTs from either side and above, viewable 80+
degrees, but do fall off rapidly from below (could be problem where children
sit on the floor looking up at the TV).
| Quote: | - higher emissivity (brighter)
|
I think this is maybe true, but where would it be an advantage? If you are
viewing in a room with lots of ambient light, then the greater reflectivity
of a CRT still makes it difficult to see the picture, despite the increase
in brightness, the matt finish on an LCD is actually better in this respect,
while if you are viewing in a darkened room, you don't need the extra
brightness.
| Quote: | OTOH LCD is definitely the way forward, and I am waiting for the price to
fall. Currently a higher resolution 42" LCD screen is ££££, whereas CRT
price's have fallen dramatically.
|
Yes LCDs are coming down, and forcing CRTs down in front of them. |
|
| Back to top |
|
|
Jan Panteltje
Guest
|
| Posted:
Wed Sep 21, 2005 12:08 am Post subject:
Re: Q regarding television noise |
|
|
On a sunny day (Tue, 20 Sep 2005 18:08:06 +0100) it happened "Java Jive"
<java@evij.com> wrote in <43306971@news.greennet.net>:
| Quote: | Thats said, here are some contras of LCD:
Let's assume a set lifetime of at least 7 years (normal for CRT).
1) How many defective pixels and where will there be in your LCD (after 7
years), remember ONE defective pixel is like flee poop (if black) on
the
middle of your screen, or if white even worse.
If you see dead pixels in the shop, you don't buy that one in the same way
you don't buy a CRT with a scratched screen. I've had both of my LCDs for
half that time, there are and have been no dead pixels.
Good! |
| Quote: | If you are not a CRT diehard, you should apply similar reasoning to CRTs. I
note that you don't, so I will: Assuming they are fortunate enough to be so
in the beginning, a rare thing in itself, how many CRTs will still be in
perfect adjustment after seven years?
As you say, that is not a CRT issue but what you call 'delivery' issue. |
Convergence in modern CRT is very good, and the electronics is very stable.
That givens there ARE a lot of CRT TV sets out there that are aligned
horribly, but few weeks ago I walked into the store here and the LCDs were
completely wrong adjusted, white clipping, if I was Philips I would send
somebody to department stores like V&D here to teach them how to adjust
a set, people will NEVER buy the way that was set up.
And this is ASSUMING Philips can be better.
| Quote: | 2) How long does your (if any) backlight last, and how much does it cost
to
replace.
Both still going. How long will your tube last?
Well, you know I had a television repair shop, and a good tube last >10 years |
if not longer.
I have a small portable here that is 30 years old (transistor).
Its tube is bad..
I have an old cash terminal with BW tube in the attic, it is 35 years
old and the tube is 100%.
You milage may vary.
| Quote: | 3) The gamma on ALL the LCDs I have seen in the shops suck, a CRT has
gamma 1/y^(2.2) by nature.
In case of LCD this is achieved electronically, and is it correct?
I've worked in the photographic trade on prints and enlargements, so have at
least a reasonable eye, and both my LCDs give better colour balance than any
CRT I can recall seeing, let alone have actually owned.
Gamma is not the same as color balance. |
As for color balance and grey scale, black level, long time ago (1980)
Philips used to make sets (K12 chassis) with automatic black level
stabilization. When the K40 chassis came, that circuit was no longer there,
I asked why, the answer was 'to save cost'.
I tell you what, I am a TV studio guy.
I grew up with PAL, many people have NEVER seen a good PAL 625 line picture
(like it can be on a profi set).
If you showed them it today, and told them it was a new system they would say
'Oh so beautiful'.
You know, it is all about sales, mpeg2 is NOT better, it has motion blur.
Some can see it, some not.
The 100Hz TVs are not better, they have plenty of artifacts, the 'flicker'
never bothered anyone, but it is a sales argument.
The 16:9 is a horrible format, ugly, but it sells new sets...
It is the art of selling, NOT the art of making a better product.
So, we can predict that once the very best (whatever tech) displays
come on the market, they will display the same old bandwidth limited crap
movies and there will be no advantage, and sets will be manufactured with
all sorts of compromise, so the next ones can be sold.
It is like MS windows, make crap, so users have to buy new every few years.
Now let's look at the quality side of TV.
Tune to BBC (1,2,3,4) look at the technical quality they produce, it is very good,
and it is free.
Now tune to RTL9, you have to pay, and it is crap technical quality.
The ONLY thing that comes out top quality these days is the commercials.
- - - So, you buy your super duper display to watch the commercials that you actually
do not want to see, so you go to the kitchen and get that food and stuff
yourself so you get overweight....
See the [food] commercial worked.
Probably the best way to stop Americans having overweight is forbid food
commercials... So no smoke, no liquor, no food, why not cut the rest too.
Oops now we have no more advertisers, no money to make programs.....
- - -
Anyways as far as LCD goes, yes sure if you are fitting in the above category
of commercial watchers then sure, hey you need a good CRT.
| Quote: |
4) The resizing needed as already mentioned for different resolutions.
I think this is a theoretical argument that is a myth in practice - I've
*never* noticed a problem with this on my LCDs. Anyway as already
explained, it's a delivery system issue.
5) The black level of a good CRT beats LCD.
As already explained, the contrast ratio of both is inadequate to cope with
dark scenes followed by light scenes with no intervening adjustment - for
optimum viewing of dark scenes with CRTs you have to reduce the brightness
to avoid picture noise, with LCDs you have to reduce the backlight level.
No this is not correct. |
The gamma of the CRT is part of the transmission signal to noise reduction
system, (the CRT is the expander), companding is done in the camera.
There is a very precise point where the CRT has to be adjusted.
For a lighter room or darker room the points are indeed different.
It is not the noise, it is the gradation.
| Quote: | 6) The power consumption story is not really that true, look at the watts
used.
I did ... LCD: Use 49W Standby 4W - *smaller* CRT: Use 52W, no standby
figure given, I suspect it's higher than 4W.
The point is to have a certain amount of light [coming from the CRT or LCD] |
when in a dark room, there is little difference.
That energy sets a minimum number of watts.
The main difference is in the defection and correction circuits for the CRT.
But the resize electronics adds some power for the LCD.
Standby is standby, and things should be off, design depend end.
| Quote: | That said, there are bad LCDs and good CRTs. As with all things,
Absolutely. |
Agreed.
_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 140,000 groups
Unlimited download
http://www.usenetzone.com to open account |
|
| Back to top |
|
|
|
|
|
|
FAQ
Memberlist
Register
Profile
Log in to check your private messages
Log in