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LCD Monitors without audible ringing?

Last response: in Computer Peripherals
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April 6, 2003 4:23:39 AM

Hello folks.

Are there any LCD monitors which do not produce an audible high pitched ringing? (or whine or hiss or whatever you call that)

If so, which ones?

Thanks much!
DuckTape
April 7, 2003 6:44:17 PM

I was irritated by the fact that my Samsung SyncMaster 770 had an audible buzzing sound. I thought maybe the grounding was bad so I used different outlets to no avail. I was considering returning the monitor when I noticed that the sound is only made when the brightness is at 90 or below. So as long as I keep the brightness level at 90-100 I have complete silence.
April 7, 2003 8:15:35 PM

Hello.

Thanks for your reply.

That brightness control is actually physically on the monitor, correct?

Then for cheaper monitors that may not have that "knob", should the brightness still be able to be controlled from the computer itself?

Thanks much!
DuckTape
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April 9, 2003 3:59:19 PM

audible noise is generated by the "back light inverter".
The brightness button is used to change the light intensity. Technically this done bei either
- PWM dimming or
- analog dimming

PWM makes audible noise while analog dimming does not.

So you have to look for a monitor with "analog dimming".

I only know of one company - Philips- using analog dimming in *some* monitor models. I cannot tell you which one.
It is not a question of size cost, high end or low end.

Unfortunately it is not featured.. so you have to write to the manufacturer to ask for the exact model number.
April 9, 2003 9:41:32 PM

Blexxun,

Thanks for your reply.

For any reason, would LCD monitors that use analog dimming have any lesser of a potential display quality than LCD monitors that use PWM dimming?

Thanks much!
DuckTape
April 11, 2003 6:10:05 AM

when analog dimming is used the operating point of the lamps is changed and the the color spectrum emitted by the lamps varies a bit. This in turn affects the color on the front screen.
Dependent on how much the spectrum is allowed to change you get a specific operating range for dimming. The resulting range is smaller compared to PWM dimming, where the operating point is always the same.
PWM means: you just turn on and off the lamps at a fixed frequency(synchronized to vertical frequency to avoid flicker). Changing the ratio of the on/off time ratio the intensity varies. When the lamp is on it has always the same operating point (=voltage & current) ).

Another drawback is the reduced dimming range (compared to PWM). This is a consequence of the allowed operating range for a CCFL (cold cathode fluorescent lamp).

There is no perfect back light system avaliable right now. LED backlight is in preparation (=> www.lumileds.com)...but I wouldnt wait for that.
April 12, 2003 8:42:18 PM

Are you saying that all new LCD monitors make noise?

I just read of another person who had a buzzing sound and fixed it by turning the brightness past 45. I also read of someone else who said their LCD is completely silent. So I'm not sure what the conclusion of this thread is.
April 18, 2003 3:45:36 PM

My new samsung 172T is completely silent at all brightness levels.

althought those brightness levels are all damn high. my graphics card doesnt include brightness controls in the drivers, so ive got some fiddling to do with windows colour management.

its a superb monitor though :) 
April 20, 2003 6:20:45 PM

my cml174sxwb is perfectly silent, and i am the kind of person who notices high pitch noises as they give me a headache, it to is also a superb monitor.
!