I just bought some (fairly cheap) IR stereo headphones. They work ok, but
with a very audible hiss even at very low volume when there is no sound from
the source (PC). This could quickly get annoying. I wondered if anyone could
tell me, is it that I just have a poor quality product or is this sort of
noise somehow inherent in the technology?
Thanks for any help.

"Marnok.com" wrote:

I just bought some (fairly cheap) IR stereo headphones. They work ok, but
with a very audible hiss even at very low volume when there is no sound from
the source (PC). This could quickly get annoying. I wondered if anyone could
tell me, is it that I just have a poor quality product or is this sort of
noise somehow inherent in the technology?

What's the brand/model ?

IR links may well be subject to some background hiss anyway. Think of all the IR
sources in the room.

Graham

"Eeyore" wrote in message
...


"Marnok.com" wrote:

I just bought some (fairly cheap) IR stereo headphones. They work ok, but
with a very audible hiss even at very low volume when there is no sound
from
the source (PC). This could quickly get annoying. I wondered if anyone
could
tell me, is it that I just have a poor quality product or is this sort of
noise somehow inherent in the technology?

What's the brand/model ?

IR links may well be subject to some background hiss anyway. Think of all
the IR
sources in the room.

Graham


Hi,

These are Pro-Luxe IR-650ST.

They were pretty cheap, and they make me look a bit like a cyberman

I tried shutting the curtains, turning the lights out and switching my
monitor off in case any of that was an IR source, none of it seemed to make
any difference.

One thing is, these phones make an awful racket - about 10x louder - when
the transmitter is off or I cover the receptors. If I had been wearing them
at full volume when I popped the batteries in and switched on, I might have
suffered damage!

Marnok.com wrote:

These are Pro-Luxe IR-650ST.

They were pretty cheap, and they make me look a bit like a cyberman

I tried shutting the curtains, turning the lights out and switching my
monitor off in case any of that was an IR source, none of it seemed to make
any difference.


You need to pipe cold liquid nitrogen into the IR receiver modules to
reduce the noise floor. Looking like a cyberman does help ;-)

Better headphones using digital encoding over radio seem to be the
answer. As it is a PC as source, why not try some Bluetooth ones?

--
Adrian C

Adrian C wrote:

Marnok.com wrote:

These are Pro-Luxe IR-650ST.

They were pretty cheap, and they make me look a bit like a cyberman

I tried shutting the curtains, turning the lights out and switching my
monitor off in case any of that was an IR source, none of it seemed to make
any difference.

You need to pipe cold liquid nitrogen into the IR receiver modules to
reduce the noise floor. Looking like a cyberman does help ;-)

You just reminded me of something.

When I was at (St Albans) School there was an almost 'spare' lab in the Science
Block. It rarely got used for lectures, so enthusiasts like the Radio Society had
use of it. At that time they downloading weather maps ! Together with 2 friends I
was working on an organic dye laser but were knackered by the impossibility of
getting optically flat mirrors. We still did some 'interesting stuff' there some
of which is utterly hilarious but since you mention LN2, we went and bought some.
Or at least 2 of us did. They went to the local 'British Oxygen' depot with a
crate full of thermos flasks and were asked on admittance if they wanted oxygen
or nitrogen !

So they went to the nitrogen section which they described as being like a petrol
pump and filled up all the thermos flasks. It wasn't even that expensive.

So we had fun trying the effects of extreme cold on many things like ICs for
example.

Then my friend Nick and I had a mischievious idea. Our next lesson was Computing,
and the teacher was well known to be rather poor with discipline, so each of us
took a boiler tube of LN2 in our jacket pockets (well insulated with several
layers of simple paper), made sure we were last into class, and before entering
poured the LN2 over our suits !

So the 2 of us entered looking like something from Dr Who, white fumes smoking
all over us and totally straight faced.. One of the guys knew we we were up to
something and unfortunately for him, was leaning back in his chair. He was so
surprised that the chair slid from under him and he got put on report.

Not a word to Nick or myself, as the 'smoke' gradually dissipated. I'm glad you
reminded me of that.

Graham

Eeyore wrote:

Adrian C wrote:

Marnok.com wrote:
These are Pro-Luxe IR-650ST.

They were pretty cheap, and they make me look a bit like a cyberman

I tried shutting the curtains, turning the lights out and switching my
monitor off in case any of that was an IR source, none of it seemed to make
any difference.
You need to pipe cold liquid nitrogen into the IR receiver modules to
reduce the noise floor. Looking like a cyberman does help ;-)

You just reminded me of something.

When I was at (St Albans) School there was an almost 'spare' lab in the Science
Block. It rarely got used for lectures, so enthusiasts like the Radio Society had
use of it. At that time they downloading weather maps ! Together with 2 friends I
was working on an organic dye laser but were knackered by the impossibility of
getting optically flat mirrors. We still did some 'interesting stuff' there some
of which is utterly hilarious but since you mention LN2, we went and bought some.
Or at least 2 of us did. They went to the local 'British Oxygen' depot with a
crate full of thermos flasks and were asked on admittance if they wanted oxygen
or nitrogen !

So they went to the nitrogen section which they described as being like a petrol
pump and filled up all the thermos flasks. It wasn't even that expensive.

So we had fun trying the effects of extreme cold on many things like ICs for
example.

Then my friend Nick and I had a mischievious idea. Our next lesson was Computing,
and the teacher was well known to be rather poor with discipline, so each of us
took a boiler tube of LN2 in our jacket pockets (well insulated with several
layers of simple paper), made sure we were last into class, and before entering
poured the LN2 over our suits !

When was this?
Presumably a long time ago, before your '37 years as a pro-audio designer'.
So how did 'downloading weather maps' work then?
I remember some physics students at college doing silly things with
liquid nitrogen,
such as pouring it over their hands. It apparently didn't feel too cold
because of the layer of gaseous nitrogen that acted as an insulator.

--
Eiron.

"Eeyore" wrote in
message
"Marnok.com" wrote:

I just bought some (fairly cheap) IR stereo headphones.
They work ok, but with a very audible hiss even at very
low volume when there is no sound from the source (PC).
This could quickly get annoying. I wondered if anyone
could tell me, is it that I just have a poor quality
product or is this sort of noise somehow inherent in the
technology?

What's the brand/model ?

IR links may well be subject to some background hiss
anyway. Think of all the IR sources in the room.

Apparently nobody is using high-quality wireless digital links.

If one were of the do-it-yourself persuasion, one might be able to cobble
together a high-quality portable listening device out of SP/DIF running over
existing wireless video technology.

I've used a laptop accessing a music server over WiFi for the general
purpose, but of course this lacked real-time broadcast source support. I
understand that there are wireless phones and PDAs that could do similar
things via a local LAN.

Marnok.com wrote:
I just bought some (fairly cheap) IR stereo headphones. They work ok, but
with a very audible hiss even at very low volume when there is no sound from
the source (PC). This could quickly get annoying. I wondered if anyone could
tell me, is it that I just have a poor quality product or is this sort of
noise somehow inherent in the technology?
Thanks for any help.


You get what you pay for? I've got a pair of Philips cheapies that use
analogue modulation on IR, they're sitting in the cupboard waiting to
get thrown out, they sound that bad. Just about useable for low fidelity
speech, IMO.

In theory, digital transmission using IR can be made as clean as CD or
DVD. In practice, it's not cheap or easy to do it that way.

--
Tciao for Now!

John.

John Williamson wrote:

I just bought some (fairly cheap) IR stereo headphones.
They work ok, but with a very audible hiss even at very
low volume when there is no sound from the source (PC).
This could quickly get annoying. I wondered if anyone
could tell me, is it that I just have a poor quality
product or is this sort of noise somehow inherent in the
technology?
Thanks for any help.
You get what you pay for? I've got a pair of Philips
cheapies that use analogue modulation on IR, they're
sitting in the cupboard waiting to get thrown out, they
sound that bad. Just about useable for low fidelity
speech, IMO.

In theory, digital transmission using IR can be made as
clean as CD or DVD. In practice, it's not cheap or easy to
do it that way.

I wonder if gain is partly controlled by carrier amplitude,
to compensate for changes in IR signal strength as you move
about? That could explain why noise, from receiving circuit
and background, gets so much worse in the absence of a
signal.

Assuming the listener's head is itself not a noisy IR
source, then the the high noise when the receptors are
blocked must come from the combination of a noisy receiving
circuit and high gain.

Perhaps it might be worth trying to return them for a
refund?

Ian

"Ian Iveson" wrote in message
...
John Williamson wrote:

I just bought some (fairly cheap) IR stereo headphones. They work ok,
but with a very audible hiss even at very low volume when there is no
sound from the source (PC). This could quickly get annoying. I wondered
if anyone could tell me, is it that I just have a poor quality product
or is this sort of noise somehow inherent in the technology?
Thanks for any help.
You get what you pay for? I've got a pair of Philips cheapies that use
analogue modulation on IR, they're sitting in the cupboard waiting to get
thrown out, they sound that bad. Just about useable for low fidelity
speech, IMO.

In theory, digital transmission using IR can be made as clean as CD or
DVD. In practice, it's not cheap or easy to do it that way.

I wonder if gain is partly controlled by carrier amplitude, to compensate
for changes in IR signal strength as you move about? That could explain
why noise, from receiving circuit and background, gets so much worse in
the absence of a signal.

Assuming the listener's head is itself not a noisy IR source, then the the
high noise when the receptors are blocked must come from the combination
of a noisy receiving circuit and high gain.

Perhaps it might be worth trying to return them for a refund?

Ian


Yes, I think I might try the refund route and maybe look at a more expensive
set. If the shop thinks this model ought to be quieter, I'll be happy to try
another pair in store and have a listen. I don't mind a bit of noise, but
this level could get annoying. (I might get my head examined again, I don't
think the doctors checked for IR emissions, I can change the channel on my
TV by concentrating and blinking, is that a bad sign?)

Thanks everyone for you help. I don't know much about headphones and audio
equipment, all I wanted was wireless so I wouldn't keep catching the wire on
something. I went for IR because I was worried that radio signals might
interfere with or suffer from interference more readily, also that the radio
waves might not be good for me in prolonged use. I'll shop around more.