Last night I was watching/listening to UPN. All of a sudden the audio ramped to a very high cracklying level and then dropped back down to normal listening level. This happened twice.

It was a crackle sound and not like the audiotrack itself had been boosted. But did appear to be coming from the speakers.

Of course the better half thought the sky was falling in.

I have also noticed a crackle when the scene changes quickly but was told that this was a Plasma phenomenom.

This time it sounded more like audio and the video screen did not change.

This is the first time I have experienced this while watching a show.

Does anyone think it was a broadcast signal scramble problem ?

I am not ruling out the equipment.

I am not using a secondary amplifier. I am using the built in amp and speakers which is all part of the Pioneer Plasma display.

And I will add that I watched that HD miniseries about Rome last night on another channel and had perfect picure and sound.

-Don B

This message was edited by barlow on 07/06/05 12:42 ET.

What device delivers UPN to your audio/video receiver? Do you have a digital AND analog connection, or only one of them? Incidentally, I assume this was not HD because you did not say UPN HD...was it HD? Satellite or cable? Antenna?


If the sound were of such a high level that the ends of the woofer voice coil forms smacked against the magnets, you would hear a crackling. I have heard this, and it is pretty awesome (in a bad way).


Please assure her that it was, but only a very small slice of it.


This makes me think you are using a mid-1980s cable box. See my first question. And I can't imagine how the plasma could be in any way related to a crackle, so I would love to see a reference on that.


I am sure it was just audio.


It probably was. A call to the cable company (DirecTV?) would be in order to see if they have had any audio problems.


Ah. THAT is why the crackle could be related to the plasma; it is not a problem with the display, it is a problem with the television. I assumed you had a display and a separate tuning device, so now I gotta ask: is this a TV and you are using the plasma TV's internal tuner to get basic cable? Is this a plasma with a built-in HD tuner (I don't know if they exist or not)?


Hmm. HD. From an internal HD tuner, or from an external satellite receiver?

Ernie Bornn-Gilman,

Sorry that I did not include my equipment !! Major mistake !!

It is a Pioneer PDP-4340HD which is a 43 inch Plasma with separate but required receiver which has both a ATSC and a NTSC tuner built in.

At the time I was experiencing the loud noise I was using the ATSC built in tuner connected to an external antenna.

I might add that the Pioneer comes with two detachable speakers which I was using at the time.

I will check tonight to see if UPN is HD or just digital on OTA broadcast.

I have also noticed a crackling sound when there is a quick programming change i.e going to commercials. I wrote Pioneer about this and was told that it is nothing to worry about. I have since read that it is associated with Plasma technology and something to do with Plasma charge build up.

But... the sound I heard the other night was much louder than this Plasma crackle sound.

-Don B

Wow. I have no idea.

The plasma charge build-up claim reminds me that old tube sets with not-too-great power supplies made noises when changing from the fade-to-black to the ad itself. Apparently many ads used very saturated whites, which taxed the power supply. I am not even hinting that there might be power supply problems with the Pioneer, just that some types of signal transition can be quite hard on a display.

I would tell Pioneer that I am not worrying about it, and that is not the issue at all, but that I want a television that puts out sound only from the audio program, not also from bits of it flopping around inside, even at the molecular level, when it has to deal with the kind of television programming that it was supposedly CREATED to display. And that I am meanwhile telling everybody who will listen, and writing on a national forum, to warn people not to buy Pioneer plasmas because who knows what models do and what don't have this problem?

"Wow. I have no idea."

Wouldn't the simplest place to look be the volume control? Maybe it's shorting out or something. Not that I'm recommending opening up your plasma, but warranty, etc.

Chances are the volume control is an IC, not a pot. That last suggestion is a good idea if you have a big rotary knob with a definite start point and stop point (and even that might not be a regular volume control, but might control voltage to an IC).

Yeah, these loud sound surges occur about one to three times a night from the speakers located internally in the plama TV. As I was reading your original post I was trying to determine if these surges in volume occurred during commercials only or during regular programming; the answer is both.

Generally, while viewing analog channels, I don't turn on the receiver (all of my components are routed thru the receiver) but when using the receiver these 'volume surges' do not occur. So the problem occurs only when using the cable box and the plasma's speakers.

As mentioned, the duration of this sound surge is brief but it will definitely get your attention! It's harsh and it's loud!!! If it happened more frequently, I'd just use the receiver all of the time.

Don't know if it's related to this scenario but I'll mention another sound item (and once again this only applies to cable box/plasma usage - no receiver): In order to achieve a 'happy medium" the volume on the plasma is set to about 50% and I leave it in this position and use only the volume control on the cable box remote to accomodate a comfortable listening level. If the setting on the plasma exceeded the 50% previously mentioned the harshness of the sound would be unaceptable. I can only describe it as unpleasant 'white noise.'

Ya' know the internal speakers in some of these plasmas are relatively inferior (to put it mildly) but there are space limitations and I also suppose thatmost people have a home theater system and never use 'em.

Just for reference, the system:

Gateway 42" HD Plasma (acutally made by Sampo)
SciAtlanta 8300HD DVR box
Yamaha RX-V2400 receiver
Panasonic E-60 DVD recorder
Definitive Techs Mythos Ones, Three, Gems, and more and a a 140lb SVS PB12-Plus 2 sub big enough to accomodate your 800 lb. gorilla (if you have one...)

-GeorgeM

So since all components are routed through the receiver, when you use the cable box and the plasma's speakers, you are somehow getting the cable box audio through the receiver which is turned off. Right? Or does the cable box have a second audio output, and one goes to the plasma while the other goes to the receiver?

If you are indeed running audio through the receiver while it is turned off, the surge could be caused by some kind of accumulation of voltage in circuits attached to the signal path, but not activated by the receiver being on; it could happen that the signal path slams to a high impedance for a moment while something discharges. This would give you a volume surge.

If this is how it is wired, and you turn on the receiver but leave its volume all the way down (this is just to see what happens when its circuits are energized), does the problem stop?


That is called distortion and is probably the result of the cable box's output being too high of a voltage for the plasma to handle. It won't hurt the plasma, just will sound bad.

E B-G, thanks for your response.

I am running two Audio Outs from the Cable Box (SA 8300 HD DVR): an Optical Audio Out to the receiver and an Audio Out (RCA cables Left and Right) to the Plasma.

I tried what you suggested (Receiver on with low volume) and did not notice any volume surge from the plasma's speakers. However, I also have NOT noticed the problem when I have the Receiver off but that may be due to the sporadic incidence of these 'surges;' i.e. they may be absent for a couple of days and then you may hear them two or three times in an hour.

In any case, if I detect their presence I'll fire up the Receiver (at low volume) as you suggested and see what events occur (or not occur).

Thanks again for your response,

-GeorgeM

"the surge could be caused by some kind of accumulation of voltage in circuits attached to the signal path,"

No it can't.

Maybe there's a knot in a wire.

I'll bite: what is the circuit topology in his unit?

If you don't know that, how do you know that it CAN'T? I would be the first to say it would be weird and totally unexpected, but "can't" is a bit strong.

Consider that if the input circuit were for some strange reason a common-emitter-wired NPN transistor with an emitter resistor and a capacitor across it, and the following transistor were a PNP. Don't ask me why this would be the topology: you said CAN'T.

When this circuit is powered down, both the emitter and collector of the NPN are at ground (as Vcc is at ground), so the positive and negative halves of the input signal give different results. The positive parts could charge the emitter capacitor...if enough signal came through, that capacitor could charge enough to turn on the PNP transistor, dropping the voltage across the capacitor quite a bit, although not to zero.

Such an occurrence would change the impedance seen by the signal. THIS is the type of thing that I said "could" possibly cause a problem.

I will now be the first to say it is totally unlikely, because if that impedance change were to change the voltage of the signal going to the other amp, then there would have been a much worse problem before the impedance change: the current flowing into the capacitor would have made the input impedance look like a diode; this would have then messed up the audio going to the other amp. In fact, this is the mechanism of horrible distortion that occurs if a signal is y-connected to an older amp and distortion occurs at the main amp when the old amp is turned off.

" but "can't" is a bit strong"

Not when dealing with reality and common sense.