Mains filters
 

In ,
Arfa Daily typed:

As I recall, it was originally designed as an article for Practically
Witless ( or was that Practical Wireless ? ) magazine. It *was*
designed by a bunch of Texas engineers at Bedford, but I'm not so
sure about the " in the bar " bit. Several of us built them from
Henry's Radio kits, and I think that for it's day, it represented
pretty much state of the art for what any of us could afford. I seem
to remember that its specifications were beyond anything that we had
ever heard. A friend of mine that built one, did that power upgrade
to his, and used it to drive his quad electrostatics, and I'm sure I
recall it sounding superb. I built a 'standard' version, and used it
to drive my EMI 13 x 8's, with 6 x 4 mids ( remember those - they
came as a pair ) rounded off with an Eagle duralumin dome tweeter,
and Eagle 3 way crossover. At the time, I thought it was the dogs ...

Yes, I built my own. Drove to Bedford and bought a kit from the original
manufacturers. Freq response, THD and stuff were leading edge at the time
and it sounded great to me through my Wharfedales (which have only just
expired). My Texan still works and the only problems were worn out volume
controls which I changed around 1995. Design was quite innovative with high
slew-rate op-amps at the front end.

Jo

Mains filters
 

"tony sayer" wrote in message
...
In article , Iain Churches
writes

People seem to think they want mains filters, and the couple of
phone calls that I made this afternoon convinced me that the demand
is certainly there (particularly in the UK!!) so a smart manufacturer
gives the punters what they (think they) want.

Yep guess your right.. Sometimes wonder if I ought do the same thing
con the gullible!....
--



Don't set yoursef up as judge and jury, Tony.
People know what they think they want, so if
you are smart you will get that soldering iron
out, and give it to them:-)

Iain

Mains filters
 

"tony sayer" wrote in message
...
In article , Iain Churches
writes

"Jim Lesurf" wrote in message
...


FWIW If you are worried about 'RF' then you should also worry about
interference which is directly radiated into units. e.g a mobile phone
in
the same room as the audio system, coupling in via the speaker leads. A
mains filter will have no effect on this. Hence it is the kind of thing
the
designer should have considered...

Hello Jim. That was to be my next question. In some digital production
suites, the use of mobile phones is strictly forbidden, and the
receptionist
takes them from clients as they come in the door.

Not a bad idea for more reasons than one!..


The first time I came across this was after someone had used a mobile
while a digital backup was being made to Exabite. The streamer failed
to load it the next day. The tape was sent to the workstation manufacturer
who pronounced that it had been rendered unreadable by GSM traffic.

Iain

Mains filters
 

In article , Iain Churches
wrote:

"Jim Lesurf" wrote in message
...


FWIW If you are worried about 'RF' then you should also worry about
interference which is directly radiated into units. e.g a mobile phone
in the same room as the audio system, coupling in via the speaker
leads. A mains filter will have no effect on this. Hence it is the
kind of thing the designer should have considered...

Hello Jim. That was to be my next question. In some digital production
suites, the use of mobile phones is strictly forbidden, and the
receptionist takes them from clients as they come in the door.

Precautionary principle. There may be a similar 'ban' in some hospitals,
etc, to avoid the risk of interference with instrumentation.

FWIW The Physics dept which I still give occasional lectures has had a ban
on the use of mobile phones on the premises for some years. Main reason
being the risk that delicate measurements with cobbled-together labgear may
be ruined. Also to stop idiot undergrads having their phone sound off
during a lecture :-) ... or even during an *exam* as I have encountered on
one occasion when invigilating.

Following the above incident I took to including in my preamble when chief
invigilator a warning that any phone that sounded during the exam would be
removed from the student and flung out the window as hard and as far as
possible. Perhaps this should become part of the exam rubric... :-)


Is coupling via speaker cables the only way that mobile phones can
affect a domestic system?

In principle, it can enter via any wiring or any gaps in metal casework.

Do manufacturers take mobile phones into consideration, and how?

I assume it would vary with the resources of the makers in question.
However it is easy enough these days to simply try using a mobile right
next to the unit and seeing what effect (if any) it has upon it. There are,
I think, some EU 'rules' about this nowdays - which prompted some makers to
fit filters and then encourage users to snip them out as they 'degraded
performance'. sigh However as I'm not in the biz anymore, I don't know
the current details I'm afraid.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Mains filters
 

In article , Jo
wrote:
In , Arny Krueger
typed:


Most power amps already have chokes in series with their output
terminals.
As they should. The Texan didn't.

A snag here is that some designers feel that an output choke increases the
HF o/p impedance and degrades the sound. Classic example being the older
Naim power amp designs which just used a 0.22 Ohm resistor...

.... and then may require about 10microH of lead inductance to be stable.
:-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Mains filters
 

In article , tony sayer

wrote:



Well TAXIS are FM these days and you wont hear them, you might get a bit
of hum.

Old bill is fast going off to Airwave TETRA and you will not hear him at
all!...

You may do,,, ;- The TETRA mobiles are pulsed, so may produce AM
envelope demod of the data pulses if they find enough nonlinearity in a
suitable place. However unless you are worried about a police raid, the
powers reaching your audio gear should be well below what you get when
someone uses a mobile phone in the room.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Mains filters
 

"Iain Churches" wrote in message
...

"tony sayer" wrote in message
...
In article , Iain Churches
writes

"Jim Lesurf" wrote in message
...


FWIW If you are worried about 'RF' then you should also worry about
interference which is directly radiated into units. e.g a mobile phone
in
the same room as the audio system, coupling in via the speaker leads. A
mains filter will have no effect on this. Hence it is the kind of thing
the
designer should have considered...

Hello Jim. That was to be my next question. In some digital production
suites, the use of mobile phones is strictly forbidden, and the
receptionist
takes them from clients as they come in the door.

Not a bad idea for more reasons than one!..


The first time I came across this was after someone had used a mobile
while a digital backup was being made to Exabite. The streamer failed
to load it the next day. The tape was sent to the workstation
manufacturer
who pronounced that it had been rendered unreadable by GSM traffic.

Iain




When I was presenting regular live broadcasts on ILR, the station required
that studio guests had their mobiles switched off. Not only interviewees and
muso's but the folk who legitimately get past the glass for the 'thrill' of
on-air sightseeing ;-) Its enough describing the studio to them in music
breaks without the mating calls of mobiles (Analogue desk then). At least
we had no problems with that kind of interference and of course observers
obeyed the red light.... except for the one not so memorable school kid who
broke wind loudly...

Mike

Mains filters
 

"Mike Gilmour" wrote in message
...

"Iain Churches" wrote in message
...

"tony sayer" wrote in message
...
In article , Iain Churches
writes

"Jim Lesurf" wrote in message
...


FWIW If you are worried about 'RF' then you should also worry about
interference which is directly radiated into units. e.g a mobile phone
in
the same room as the audio system, coupling in via the speaker leads.
A
mains filter will have no effect on this. Hence it is the kind of
thing
the
designer should have considered...

Hello Jim. That was to be my next question. In some digital production
suites, the use of mobile phones is strictly forbidden, and the
receptionist
takes them from clients as they come in the door.

Not a bad idea for more reasons than one!..


The first time I came across this was after someone had used a mobile
while a digital backup was being made to Exabite. The streamer failed
to load it the next day. The tape was sent to the workstation
manufacturer
who pronounced that it had been rendered unreadable by GSM traffic.

Iain




When I was presenting regular live broadcasts on ILR, the station required
that studio guests had their mobiles switched off. Not only interviewees
and muso's but the folk who legitimately get past the glass for the
'thrill' of on-air sightseeing ;-) Its enough describing the studio to
them in music breaks without the mating calls of mobiles (Analogue desk
then). At least we had no problems with that kind of interference and of
course observers obeyed the red light.... except for the one not so
memorable school kid who broke wind loudly...

Mike

You weren't in " The Tripods " by any chance ?

Arfa

Mains filters
 

"Arfa Daily" wrote in message
...

"Mike Gilmour" wrote in message
...

"Iain Churches" wrote in message
...

"tony sayer" wrote in message
...
In article , Iain Churches
writes

"Jim Lesurf" wrote in message
...


FWIW If you are worried about 'RF' then you should also worry about
interference which is directly radiated into units. e.g a mobile
phone in
the same room as the audio system, coupling in via the speaker leads.
A
mains filter will have no effect on this. Hence it is the kind of
thing
the
designer should have considered...

Hello Jim. That was to be my next question. In some digital production
suites, the use of mobile phones is strictly forbidden, and the
receptionist
takes them from clients as they come in the door.

Not a bad idea for more reasons than one!..


The first time I came across this was after someone had used a mobile
while a digital backup was being made to Exabite. The streamer failed
to load it the next day. The tape was sent to the workstation
manufacturer
who pronounced that it had been rendered unreadable by GSM traffic.

Iain




When I was presenting regular live broadcasts on ILR, the station
required that studio guests had their mobiles switched off. Not only
interviewees and muso's but the folk who legitimately get past the glass
for the 'thrill' of on-air sightseeing ;-) Its enough describing the
studio to them in music breaks without the mating calls of mobiles
(Analogue desk then). At least we had no problems with that kind of
interference and of course observers obeyed the red light.... except for
the one not so memorable school kid who broke wind loudly...

Mike

You weren't in " The Tripods " by any chance ?

Arfa


Sorry thats not me. The part of Jack in 'The Tripods' was played by
another Michael Gilmour. I've got the perfect face for radio ;-)

Mike

Mains filters
 

In article , Jim Lesurf jcgl@st-
and.demon.co.uk writes
In article , tony sayer

wrote:



Well TAXIS are FM these days and you wont hear them, you might get a bit
of hum.

Old bill is fast going off to Airwave TETRA and you will not hear him at
all!...

You may do,,, ;- The TETRA mobiles are pulsed, so may produce AM
envelope demod of the data pulses if they find enough nonlinearity in a
suitable place. However unless you are worried about a police raid, the
powers reaching your audio gear should be well below what you get when
someone uses a mobile phone in the room.

If U reckon U can decode the TETRA old bills using Jim, then there would
be a lot of people very interested in that!....

--
Tony Sayer