The digital music channels in our cable TV service occasionally
experience some kind of switching glitch that sounds dangerous
to high-end audio systems. What causes it? It's definitely not the
kind of chattering you hear when a CD is bad. I did a Google search of
rec.audio newsgroups and didn't find anything on this. Does it happen to
anybody?

In a year of listening about an hour a day, I've heard this kind of
thing maybe a half-dozen times. Yesterday morning was the
worst of all. I had the volume turned up moderately and heard what
sounded like a rifle shot. The TV image twitched at the same moment.
As I was pondering whether to bail out to a CD, another sharp crack
occurred. I switched to a CD to see if everything was okay. It wasn't.
The right channel frequencies had horrible distortion at high volume.
I turned off my system until I had time to examine the situation in
detail. An hour later, I turned it on, put a CD in...and everything
was normal. My guess is that the tweeter coils actually had to cool
off before coming back to normal. So far, there appears to be no
permanent damage.

Well depending how high end your speakers are they may not have fuses
or circuit breakers as they tend to add odd order harmonics to the
tweeter's output. HIgher end speakers usually don't have fuses or
breakers. Also if the clip is bad enough your amp's protection should
kick in.

If you have sufficient power then possibly (unless you have the volume
turned up pretty high) your amp may not clip enough to cause damage.
Cliping will damage tweeters whereas high levels of clean power is
more likely to burn out low frequency drivers (woofers) if your
continuous output power exceeds your woofer's rated maximum continuous
power handling capacity.


Are you sure those glitches are really that loud? They can sound
extremely loud when they are so dramatically different from the
material to which you're listening.

In article , voltar-the
friendly toad wrote:
Well depending how high end your speakers are they may not have fuses
or circuit breakers as they tend to add odd order harmonics to the
tweeter's output. HIgher end speakers usually don't have fuses or
breakers.

How do fuses and circuit breakers do this? Explanation please, with a
basis more scientific than I have seen in the ilk of "Absolute Sound".

- Don Klipstein )

Don Klipstein wrote:
In article , voltar-the
friendly toad wrote:
Well depending how high end your speakers are they may not have fuses
or circuit breakers as they tend to add odd order harmonics to the
tweeter's output. HIgher end speakers usually don't have fuses or
breakers.

How do fuses and circuit breakers do this? Explanation please, with a
basis more scientific than I have seen in the ilk of "Absolute Sound".

The idea here is that fuses are nonlinear devices, even well before they
blow. They heat up as current flows through them, which increases their
resistance a little in the process.

The time constant on them is low enough and the degree of change low
enough that I can't imagine you could hear it on a tweeter, but I could
see it being audible on a woofer.

Circuit breakers are a totally different issue, in that they wind up
adding a nonlinear and possibly reactive solenoid in the signal path.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article , Scott Dorsey wrote:
Don Klipstein wrote:
In article , voltar-the
friendly toad wrote:
Well depending how high end your speakers are they may not have fuses
or circuit breakers as they tend to add odd order harmonics to the
tweeter's output. HIgher end speakers usually don't have fuses or
breakers.

How do fuses and circuit breakers do this? Explanation please, with a
basis more scientific than I have seen in the ilk of "Absolute Sound".

The idea here is that fuses are nonlinear devices, even well before they
blow. They heat up as current flows through them, which increases their
resistance a little in the process.

The time constant on them is low enough and the degree of change low
enough that I can't imagine you could hear it on a tweeter, but I could
see it being audible on a woofer.

Circuit breakers are a totally different issue, in that they wind up
adding a nonlinear and possibly reactive solenoid in the signal path.

Aren't those pretty linear until something moves?

I am aware of the nonlinearity of inductors with ferromagnetic
materials, but that tends to be negligible when much of the magnetic flux
path is through air.

I thought breakers for tweeters were thermal devices anyway, although it
has been quite a few years since I looked at a tweeter breaker.

- Don Klipstein )

Don Klipstein wrote:
Kludge writes:

Circuit breakers are a totally different issue, in that they wind up
adding a nonlinear and possibly reactive solenoid in the signal path.

Aren't those pretty linear until something moves?

I am aware of the nonlinearity of inductors with ferromagnetic
materials, but that tends to be negligible when much of the magnetic flux
path is through air.

Good point. Hmm... some types of solenoids have the core always within
the field... others (like most relays) have the field itself open until
it pulls in. I guess I ought to take apart a circuit breaker and see.

I thought breakers for tweeters were thermal devices anyway, although it
has been quite a few years since I looked at a tweeter breaker.

All kinds of stuff gets stuck in front of tweeters. Some are solid state
devices, even. I won't even mention the dome light bulbs.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:

All kinds of stuff gets stuck in front of tweeters. Some are solid state
devices, even. I won't even mention the dome light bulbs.

That's so you can find your high end in the dark.

--
ha

"Scott Dorsey" wrote in message
...
Don Klipstein wrote:
Kludge writes:

Circuit breakers are a totally different issue, in that they wind up
adding a nonlinear and possibly reactive solenoid in the signal path.

Aren't those pretty linear until something moves?

I am aware of the nonlinearity of inductors with ferromagnetic
materials, but that tends to be negligible when much of the magnetic flux
path is through air.

Good point. Hmm... some types of solenoids have the core always within
the field... others (like most relays) have the field itself open until
it pulls in. I guess I ought to take apart a circuit breaker and see.

I thought breakers for tweeters were thermal devices anyway, although
it
has been quite a few years since I looked at a tweeter breaker.

All kinds of stuff gets stuck in front of tweeters. Some are solid state
devices, even. I won't even mention the dome light bulbs.
--scott

The current popular protective device is the polyfuse, a self-resetting
solid state fuse.
The construction is a conductive polymer that changes phase rapidly above a
set temperature.
Every USB port is protected by a polyfuse. They are phenomenally reliable
and noninductive, though they do have a resistance in the tenths of ohms.

Scott Dorsey wrote:

All kinds of stuff gets stuck in front of tweeters. Some are solid state
devices, even. I won't even mention the dome light bulbs.

I remember the first time I became aware of the light bulbs inside some PA
speakers. I was playing bass at a wedding reception, and we had the
undersized makeshift rig running quite loud. I suddenly noticed yellow
light visible through the reflex ports pulsing in time with the music, and
thought we'd set something on fire!

--
Mark.

(voltar-the friendly toad) wrote in message . com...
Are you sure those glitches are really that loud? They can sound
extremely loud when they are so dramatically different from the
material to which you're listening.

Yes, they were loud...and it turns out there is permanent damage,
though not of the kind that simply killed any of the speakers dead.
I'll have to study the situation in detail this weekend when I have
enough time. Stay tuned...and I'd sure like to hear from the
rec.video.cable-tv readers of my crossposting regarding these acoustic
thunderbolts.

Robert Morein wrote:

The current popular protective device is the polyfuse, a self-resetting
solid state fuse.
The construction is a conductive polymer that changes phase rapidly above a
set temperature.
Every USB port is protected by a polyfuse. They are phenomenally reliable
and noninductive, though they do have a resistance in the tenths of ohms.

Have you got a manufacturer I can check out? This sounds interesting.

The problem with speaker protection devices is that you need something that
acts fast, but you need something that has a very abrupt transition point with
little effect below the transition.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Hi Charles
I just got a digital box last week and had what sounds like your same
problem,
loud cracking and sometimes fading of the music....I just had the cable guy
out last night with a signal meter. It turned out that I was maginally low
on the signal. On my line it was -7db as calibrated on his meter, he
said it should be 0db. I do have a splitter before the box, so he
put an amplifier right before the box which boosted the signal to 0db
(where they say it should be). So far, so good!!! Hope this helps
in getting your problem solved.

"Charles Packer" wrote in message
om...
The digital music channels in our cable TV service occasionally
experience some kind of switching glitch that sounds dangerous
to high-end audio systems. What causes it? It's definitely not the
kind of chattering you hear when a CD is bad. I did a Google search of
rec.audio newsgroups and didn't find anything on this. Does it happen to
anybody?

In a year of listening about an hour a day, I've heard this kind of
thing maybe a half-dozen times. Yesterday morning was the
worst of all. I had the volume turned up moderately and heard what
sounded like a rifle shot. The TV image twitched at the same moment.
As I was pondering whether to bail out to a CD, another sharp crack
occurred. I switched to a CD to see if everything was okay. It wasn't.
The right channel frequencies had horrible distortion at high volume.
I turned off my system until I had time to examine the situation in
detail. An hour later, I turned it on, put a CD in...and everything
was normal. My guess is that the tweeter coils actually had to cool
off before coming back to normal. So far, there appears to be no
permanent damage.

"Dennis Leiterman" wrote in message
news
Hi Charles
I just got a digital box last week and had what sounds like your same
problem,
loud cracking and sometimes fading of the music....I just had the cable
guy
out last night with a signal meter. It turned out that I was maginally
low
on the signal. On my line it was -7db as calibrated on his meter, he
said it should be 0db.

Oh boy. I hate reading things like this.

weitrhino



I do have a splitter before the box, so he
put an amplifier right before the box which boosted the signal to 0db
(where they say it should be). So far, so good!!! Hope this helps
in getting your problem solved.

"Charles Packer" wrote in message
om...
The digital music channels in our cable TV service occasionally
experience some kind of switching glitch that sounds dangerous
to high-end audio systems. What causes it? It's definitely not the
kind of chattering you hear when a CD is bad. I did a Google search of
rec.audio newsgroups and didn't find anything on this. Does it happen to
anybody?

In a year of listening about an hour a day, I've heard this kind of
thing maybe a half-dozen times. Yesterday morning was the
worst of all. I had the volume turned up moderately and heard what
sounded like a rifle shot. The TV image twitched at the same moment.
As I was pondering whether to bail out to a CD, another sharp crack
occurred. I switched to a CD to see if everything was okay. It wasn't.
The right channel frequencies had horrible distortion at high volume.
I turned off my system until I had time to examine the situation in
detail. An hour later, I turned it on, put a CD in...and everything
was normal. My guess is that the tweeter coils actually had to cool
off before coming back to normal. So far, there appears to be no
permanent damage.

"Scott Dorsey" wrote in message
...
Robert Morein wrote:

The current popular protective device is the polyfuse, a self-resetting
solid state fuse.
The construction is a conductive polymer that changes phase rapidly above
a
set temperature.
Every USB port is protected by a polyfuse. They are phenomenally reliable
and noninductive, though they do have a resistance in the tenths of ohms.

Have you got a manufacturer I can check out? This sounds interesting.

The problem with speaker protection devices is that you need something
that
acts fast, but you need something that has a very abrupt transition point
with
little effect below the transition.
--scott
--
http://www.wickmannusa.com/html/pptcsm.html

"Dennis Leiterman" wrote in message igy.com...
Hi Charles
I just got a digital box last week and had what sounds like your same
problem,
loud cracking and sometimes fading of the music....I just had the cable guy
out last night with a signal meter. It turned out that I was maginally low
on the signal. On my line it was -7db as calibrated on his meter, he
said it should be 0db. I do have a splitter before the box, so he
put an amplifier right before the box which boosted the signal to 0db
(where they say it should be). So far, so good!!! Hope this helps
in getting your problem solved.


As it turns out, the day before the glitch I experienced, my cable
company finally agreed that the problems I had been having with their
modem service were due to their network, and would be fixed by the
next day. Who knows...maybe in the course of whatever they were doing
to fix that, they sent all kinds of glitches down the line. At any rate,
I've discovered that the permanent damage was to my preamp. This is
a relief, since it's ancient and I don't mind having an excuse to
replace it.

I may open a can of worms here, but let it serve to educate me.

Firstly, I have strong doubts about the digital cable music causing a
failure in your pre-amp. That is to say, I can't see a reason for it. I am
assuming you have audio outputs from the box directly into your pre-amp.
The box is a "line level" device the same as any other line level device.
The pre-amp controls the signal being fed into the power amplifier. The
amplifier would only reproduce what is sent into it, right?

Secondly, a loud 'pop' would be a considerable change in amplitude of a
given signal relative to the volume setting. This could not come from the
digital box which is a fixed "line level" device. I would think it far more
likely the fault was lurking within the pre-amp channel all along. I
suspect a capaciter has blown. It's sudden discharge created the change in
amplitude.

I now defer to those with greater insight.

weitrhino


"Charles Packer" wrote in message
om...
"Dennis Leiterman" wrote in message
igy.com...
Hi Charles
I just got a digital box last week and had what sounds like your same
problem,
loud cracking and sometimes fading of the music....I just had the cable
guy
out last night with a signal meter. It turned out that I was maginally
low
on the signal. On my line it was -7db as calibrated on his meter, he
said it should be 0db. I do have a splitter before the box, so he
put an amplifier right before the box which boosted the signal to 0db
(where they say it should be). So far, so good!!! Hope this helps
in getting your problem solved.


As it turns out, the day before the glitch I experienced, my cable
company finally agreed that the problems I had been having with their
modem service were due to their network, and would be fixed by the
next day. Who knows...maybe in the course of whatever they were doing
to fix that, they sent all kinds of glitches down the line. At any rate,
I've discovered that the permanent damage was to my preamp. This is
a relief, since it's ancient and I don't mind having an excuse to
replace it.

"weitrhino" wrote in message ...
Firstly, I have strong doubts about the digital cable music causing a
failure in your pre-amp. That is to say, I can't see a reason for it. I

Indeed, I'm beginning to doubt it too. The preamp subsequently
exhibited some more weird behavior upon being turned on in the
morning. After some exchanging of cables, fiddling with switches,
it went away and hasn't returned, so far. And, incidentally,
Starpower hadn't fixed my modem problem, as they said. This morning
I had to disconnect the TV box from the cable feed to get a high
enough modem level... Things are back to normal!

(Scott Dorsey) wrote in message ...
Robert Morein wrote:

The current popular protective device is the polyfuse, a self-resetting
solid state fuse.
The construction is a conductive polymer that changes phase rapidly above a
set temperature.
Every USB port is protected by a polyfuse. They are phenomenally reliable
and noninductive, though they do have a resistance in the tenths of ohms.

Have you got a manufacturer I can check out? This sounds interesting.


Raychem polyfuse

Mark

On 31 Mar 2004 03:30:37 -0800, (Charles Packer)
wrote:

The digital music channels in our cable TV service occasionally
experience some kind of switching glitch that sounds dangerous
to high-end audio systems. What causes it? It's definitely not the
kind of chattering you hear when a CD is bad. I did a Google search of
rec.audio newsgroups and didn't find anything on this. Does it happen to
anybody?


This is a pretty common occurance. It will happen when you have a bad
signal or lose the digital data stream all of a sudden. Try
unplugging the cable from the cable box while the music is playing to
see if the same thing happens. Depending on the hardware/software on
your box, some will handle the situation differently.