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So, what's the point of that, then ... ?
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Arfa Daily
Jan 2, 2013, 11:45:12 AM1/2/13
to
Today, a Denon amplifier model PMA 250 II crossed my bench. Quite old, but
then Denon gear is usually pretty good quality and long lived, and well
designed - or so I thought ...
The reported problems were that the sound level fluctuated on both channels,
and that the headphone socket did not cut the speakers. The first problem
was cured in short order by treating the function switch to a dose of
squidget juice. I gave all of the other switches and controls a little
tickle as well, for completeness.
Then I jacked in a set of headphones, and the owner was correct - the
speakers kept running. There were five wires going across to the sub-board
at the front that the socket was on, so it looked promising that it should
switch, but I was a bit puzzled as to why it actually wasn't. The socket and
board is secured to the inner front panel by a slide-on clip, so I whipped
the outer front panel off, pulled the clip, and withdrew the board and
socket so I could have a look underneath and see what was going on. I was
mighty surprised to see that although the PCB had all the right pads and
holes for a five pin socket, only a 3 pin was fitted. Two of the wires in
the 5 wire ribbon were in fact connected to nothing other than dead-end
tracks. I put it back together, and went on-line to see if I could find a
user manual. When I did, I looked up the section on controls and connectors,
and found this entry :
"PHONES
The jack is used for connecting the headphones.
When the headphones are plugged in, the sound will cease to come from the
speakers (except for the English model)."
WTF is that about ? I could maybe at a pinch understand it if there was a
front panel speaker selector switch such as you see on some amps, like "OFF,
A, B, A+B", but there is no such switch on this, nor any other way that I
can see of disabling the speakers, short of disconnecting them. What is the
point, then, of having a headphone socket at all ? Why would you design it
to take a switched socket, and then exclude one model from using the
feature, effectively rendering the socket pretty much useless for its
intended purpose ? Why in particular exclude the "English" model ? It's not
as though there are any regulations here concerning headphone sockets, and
in fact I don't think that I have ever seen another amp that didn't switch
the speakers when phones were plugged in.
Because I knew that the owner was not going to believe this either, I
printed off the manual page and highlighted the relevant text, before
returning it to the store that sent it in to me ...
Arfa
then Denon gear is usually pretty good quality and long lived, and well
designed - or so I thought ...
The reported problems were that the sound level fluctuated on both channels,
and that the headphone socket did not cut the speakers. The first problem
was cured in short order by treating the function switch to a dose of
squidget juice. I gave all of the other switches and controls a little
tickle as well, for completeness.
Then I jacked in a set of headphones, and the owner was correct - the
speakers kept running. There were five wires going across to the sub-board
at the front that the socket was on, so it looked promising that it should
switch, but I was a bit puzzled as to why it actually wasn't. The socket and
board is secured to the inner front panel by a slide-on clip, so I whipped
the outer front panel off, pulled the clip, and withdrew the board and
socket so I could have a look underneath and see what was going on. I was
mighty surprised to see that although the PCB had all the right pads and
holes for a five pin socket, only a 3 pin was fitted. Two of the wires in
the 5 wire ribbon were in fact connected to nothing other than dead-end
tracks. I put it back together, and went on-line to see if I could find a
user manual. When I did, I looked up the section on controls and connectors,
and found this entry :
"PHONES
The jack is used for connecting the headphones.
When the headphones are plugged in, the sound will cease to come from the
speakers (except for the English model)."
WTF is that about ? I could maybe at a pinch understand it if there was a
front panel speaker selector switch such as you see on some amps, like "OFF,
A, B, A+B", but there is no such switch on this, nor any other way that I
can see of disabling the speakers, short of disconnecting them. What is the
point, then, of having a headphone socket at all ? Why would you design it
to take a switched socket, and then exclude one model from using the
feature, effectively rendering the socket pretty much useless for its
intended purpose ? Why in particular exclude the "English" model ? It's not
as though there are any regulations here concerning headphone sockets, and
in fact I don't think that I have ever seen another amp that didn't switch
the speakers when phones were plugged in.
Because I knew that the owner was not going to believe this either, I
printed off the manual page and highlighted the relevant text, before
returning it to the store that sent it in to me ...
Arfa
Michael A. Terrell
Jan 2, 2013, 3:51:01 PM1/2/13
to
Smarty
Jan 2, 2013, 4:13:02 PM1/2/13
to
On 1/2/2013 3:51 PM, Michael A. Terrell wrote:
They either had to make it quirky in a way that Brits would appreciate,
or to follow the great tradition of British automobile makers and
provide a way to make it leak some type of fluid.
They chose the less expensive choice.........
:D
> Arfa Daily wrote:
>>
>>
>> It sounds like they made a deal with Lucas... ;-)
Denon was left with a difficult choice when designing the British model.
>>
>>
>> It sounds like they made a deal with Lucas... ;-)
They either had to make it quirky in a way that Brits would appreciate,
or to follow the great tradition of British automobile makers and
provide a way to make it leak some type of fluid.
They chose the less expensive choice.........
:D
Michael A. Terrell
Jan 2, 2013, 5:01:49 PM1/2/13
to
of dorkness. ;-)
Tim Schwartz
Jan 3, 2013, 8:07:43 AM1/3/13
to
Happy New Year Arfa,
Well, maybe they felt that the British either use headphone or
speakers, and most people don't own both?
On the other hand, your description makes me thing that if you fitted
the switching jack to the board, you could add the switching the
customer desired...
The even dumber part is to run the speaker wires to the headphone jack
board at all if you are not going to switch them, adding all the extra
wiring for no reason, and adding the resistance of the wiring to the
speaker lines.
Best regards,
Tim Schwartz
Bristol Electronics
P.S. Who said there was a point?
On 1/2/2013 3:51 PM, Michael A. Terrell wrote:
>
Well, maybe they felt that the British either use headphone or
speakers, and most people don't own both?
On the other hand, your description makes me thing that if you fitted
the switching jack to the board, you could add the switching the
customer desired...
The even dumber part is to run the speaker wires to the headphone jack
board at all if you are not going to switch them, adding all the extra
wiring for no reason, and adding the resistance of the wiring to the
speaker lines.
Best regards,
Tim Schwartz
Bristol Electronics
P.S. Who said there was a point?
On 1/2/2013 3:51 PM, Michael A. Terrell wrote:
>
Franc Zabkar
Jan 3, 2013, 3:43:08 PM1/3/13
to
On Wed, 2 Jan 2013 16:45:12 -0000, "Arfa Daily"
<arfa....@ntlworld.com> put finger to keyboard and composed:
>The reported problems were that the sound level fluctuated on both channels,
>and that the headphone socket did not cut the speakers.
My old Mitsubishi CRT TV had two headphone sockets. One cut the
speaker, the other did not. Presumably it was to allow a hearing
impaired individual to listen to the TV via headphones while their
partner listened via the speaker. I can't imagine that this would
apply in the Denon case, though.
I'm trying to envisage some kind of safety issue, but I can't think of
any that make sense. There have been times when I've received a
deafening blast from my headphones at switch-on, or when selecting a
signal source, but that's not something that would be remedied by
unswitched speaker outputs.
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
<arfa....@ntlworld.com> put finger to keyboard and composed:
>The reported problems were that the sound level fluctuated on both channels,
>and that the headphone socket did not cut the speakers.
speaker, the other did not. Presumably it was to allow a hearing
impaired individual to listen to the TV via headphones while their
partner listened via the speaker. I can't imagine that this would
apply in the Denon case, though.
I'm trying to envisage some kind of safety issue, but I can't think of
any that make sense. There have been times when I've received a
deafening blast from my headphones at switch-on, or when selecting a
signal source, but that's not something that would be remedied by
unswitched speaker outputs.
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
Cydrome Leader
Jan 3, 2013, 3:50:25 PM1/3/13
to
Franc Zabkar <fza...@iinternode.on.net> wrote:
> On Wed, 2 Jan 2013 16:45:12 -0000, "Arfa Daily"
> <arfa....@ntlworld.com> put finger to keyboard and composed:
>
>>The reported problems were that the sound level fluctuated on both channels,
>>and that the headphone socket did not cut the speakers.
>
> My old Mitsubishi CRT TV had two headphone sockets. One cut the
> speaker, the other did not. Presumably it was to allow a hearing
I recall this. It's on par with picture-in-picture for actual usefulness.
> On Wed, 2 Jan 2013 16:45:12 -0000, "Arfa Daily"
> <arfa....@ntlworld.com> put finger to keyboard and composed:
>
>>The reported problems were that the sound level fluctuated on both channels,
>>and that the headphone socket did not cut the speakers.
>
> My old Mitsubishi CRT TV had two headphone sockets. One cut the
> speaker, the other did not. Presumably it was to allow a hearing
Michael A. Terrell
Jan 3, 2013, 7:48:14 PM1/3/13
to
Franc Zabkar wrote:
>
> On Wed, 2 Jan 2013 16:45:12 -0000, "Arfa Daily"
> <arfa....@ntlworld.com> put finger to keyboard and composed:
>
> >The reported problems were that the sound level fluctuated on both channels,
> >and that the headphone socket did not cut the speakers.
>
> My old Mitsubishi CRT TV had two headphone sockets. One cut the
> speaker, the other did not. Presumably it was to allow a hearing
> impaired individual to listen to the TV via headphones while their
> partner listened via the speaker. I can't imagine that this would
> apply in the Denon case, though.
>
> I'm trying to envisage some kind of safety issue, but I can't think of
> any that make sense.
point.
Arfa Daily
Jan 3, 2013, 7:51:23 PM1/3/13
to
"Tim Schwartz" <t...@bristolnj.com> wrote in message
news:50E5829F...@bristolnj.com...
wiring, as it's a piece of 5 way ribbon cable, but it does of course require
that two wire links are fitted somewhere - although I don't recall seeing
them at the socket PCB, so perhaps they are the other end. At the end of the
day, it's quite an old amp and it is what it is. I'm not about to start
messing about modding it, unless the owner says specifically that he wants
to pay for it as a 'proper' job. I would guess that it's either sat in his
attic for years and he's forgotten about this little foible, or he's bought
it on FleaBay and didn't realise. No matter how you look at it though, I
still think that it's a thoroughly shit-street piece of design work, and I
can't see any point in having the socket fitted at all, if it's not going to
cut the speakers ...
Arfa
Arfa Daily
Jan 3, 2013, 8:03:02 PM1/3/13
to
"Franc Zabkar" <fza...@iinternode.on.net> wrote in message
news:kdqbe81ugk26m7d35...@4ax.com...
software level control, and of course, there is a remote 'mute' function, so
the internal speakers can be turned off if I want to listen to something on
there, whilst the missus is messing about on her laptop, or whatever.
Interestingly, the on-screen 'mute' symbol disappears after about 2 minutes.
On my workshop TV, you get a bloody great red loudspeaker symbol with a bar
through it, all the time it is muted ...
With 40 yeras of experience in this game, and added to the all the combined
years of the rest of us on here, if we can't come up with a sensible reason,
then you have to assume that there *is* no sense to it. I hate it when you
get a puzzle like this though. I really would like to know what the designer
was thinking when he did this for the "English" model only. By that, do they
actually mean the "UK" model ? I can't imagine that any different version
was shipped to N.I. or Wales or Scotland. That would be a bit like having
one version for Texas, and a different one for Colorado ...
Arfa
Franc Zabkar
Jan 4, 2013, 12:15:46 AM1/4/13
to
On Fri, 4 Jan 2013 01:03:02 -0000, "Arfa Daily"
>On my workshop TV, you get a bloody great red loudspeaker symbol with a bar
>through it, all the time it is muted ...
LG?
>through it, all the time it is muted ...
Phil Allison
Jan 4, 2013, 1:15:52 AM1/4/13
to
"Arfa Daily"
>
> With 40 yeras of experience in this game, and added to the all the
> combined years of the rest of us on here, if we can't come up with a
> sensible reason, then you have to assume that there *is* no sense to it. I
> hate it when you get a puzzle like this though. I really would like to
> know what the designer was thinking when he did this for the "English"
> model only. By that, do they actually mean the "UK" model ?
The motive back then was the British hi-fi press's obsession with "damping
factor" or DF.
By omitting the wiring to and from the HP jack, Denon were able to publish
an impressive number for DF and the folk in sales thought this to be a good
idea, at least for the UK market.
.... Phil
Arfa Daily
Jan 4, 2013, 10:51:03 AM1/4/13
to
"Michael A. Terrell" <mike.t...@earthlink.net> wrote in message
news:l9qdnXr48edLu3vN...@earthlink.com...
money between a switched and unswitched socket by fitting a cheaper volume
knob ...
Arfa
Arfa Daily
Jan 4, 2013, 11:09:59 AM1/4/13
to
news:rapce85sg6agrh09p...@4ax.com...
It's actually a Bush. Two generations ago, Bush were a very well respected
indigenous manufacturer of quality consumer electronics. When I was a kid,
our household TV was a Bush. My first transistor radio which was built on a
metal chassis which had wiring points all over it (and which I've still got
somewhere) was a Bush. About one generation ago, they formed an amalgamation
with Murphy, another quality UK manufacturer, under the Rank Organisation
umbrella to become Rank Bush Murphy or RBM. It was still a wholly UK
manufacturing operation, and still produced quality products. Some years
back, like most manufacturing here and as I understand it, in the U.S. also,
they packed it all in.
Always having an eye to the main chance, some bunch of Ying Tongs bought the
Bush and Murphy names, and started badging their crap with them, and
exporting them back to the UK. Because Bush stuff used to be good, and
there's plenty of my age that had Bush stuff in their homes when they were
kids, it has continued to sell well, but most of it is now real cheapo Far
East stuff that'll just about last out its warranty if you are lucky. It's
real 'shed' and supermarket quality stuff.
To be fair, the TV in my workshop is not too bad, as long as all you are
interested in is having a picture, rather than having a 'good' picture. The
only reason that I have it is that it was 'inherited' from a dealer that I
did some work for, and he supplied the set for monitoring purposes as part
of the deal.
Is it LG inside ? I don't know. It could be, I suppose, but I doubt that it
would warrant having a chassis from a well known manufacturer like them in
it. However, if the big red speaker on the screen is characteristic of the
LG you are thinking of, then maybe it is an LG chassis ...
Arfa
indigenous manufacturer of quality consumer electronics. When I was a kid,
our household TV was a Bush. My first transistor radio which was built on a
metal chassis which had wiring points all over it (and which I've still got
somewhere) was a Bush. About one generation ago, they formed an amalgamation
with Murphy, another quality UK manufacturer, under the Rank Organisation
umbrella to become Rank Bush Murphy or RBM. It was still a wholly UK
manufacturing operation, and still produced quality products. Some years
back, like most manufacturing here and as I understand it, in the U.S. also,
they packed it all in.
Always having an eye to the main chance, some bunch of Ying Tongs bought the
Bush and Murphy names, and started badging their crap with them, and
exporting them back to the UK. Because Bush stuff used to be good, and
there's plenty of my age that had Bush stuff in their homes when they were
kids, it has continued to sell well, but most of it is now real cheapo Far
East stuff that'll just about last out its warranty if you are lucky. It's
real 'shed' and supermarket quality stuff.
To be fair, the TV in my workshop is not too bad, as long as all you are
interested in is having a picture, rather than having a 'good' picture. The
only reason that I have it is that it was 'inherited' from a dealer that I
did some work for, and he supplied the set for monitoring purposes as part
of the deal.
Is it LG inside ? I don't know. It could be, I suppose, but I doubt that it
would warrant having a chassis from a well known manufacturer like them in
it. However, if the big red speaker on the screen is characteristic of the
LG you are thinking of, then maybe it is an LG chassis ...
Arfa
Michael A. Terrell
Jan 4, 2013, 1:30:10 PM1/4/13
to
Arfa Daily
Jan 6, 2013, 11:12:46 AM1/6/13
to
"Phil Allison" <phi...@tpg.com.au> wrote in message
news:aknad2...@mid.individual.net...
Peter Walker of Quad fame espoused similar opinions a bit further back than
this unit comes from, and cited it as the reason for refusing to fit
headphone sockets to their products ...
Arfa
josephkk
Jan 7, 2013, 10:21:40 PM1/7/13
to
On Wed, 2 Jan 2013 16:45:12 -0000, "Arfa Daily" <arfa....@ntlworld.com>
wrote:
speaker cutouts on the headphone jack; but _ALL_ of them had proper
speaker switches of some sort.
YMMV
?-)
josephkk
Jan 7, 2013, 10:25:46 PM1/7/13
to
some of it came out of my nose.
?-)
Trevor Wilson
Jan 8, 2013, 3:03:38 PM1/8/13
to
switches are not the highest quality method of switching a speaker level
audio signal available.
--
Trevor Wilson www.rageaudio.com.au
Michael A. Terrell
Jan 8, 2013, 4:06:23 PM1/8/13
to
Trevor Wilson wrote:
>
> On 1/3/2013 3:45 AM, Arfa Daily wrote:
> ? but then Denon gear is usually pretty good quality and long lived, and
> ? well designed - or so I thought ...
> ?
> ? The reported problems were that the sound level fluctuated on both
> ? channels, and that the headphone socket did not cut the speakers. The
> ? first problem was cured in short order by treating the function switch
> ? to a dose of squidget juice. I gave all of the other switches and
> ? controls a little tickle as well, for completeness.
> ?
> ? Then I jacked in a set of headphones, and the owner was correct - the
> ? speakers kept running. There were five wires going across to the
> ? sub-board at the front that the socket was on, so it looked promising
> ? that it should switch, but I was a bit puzzled as to why it actually
> ? wasn't. The socket and board is secured to the inner front panel by a
> ? slide-on clip, so I whipped the outer front panel off, pulled the clip,
> ? and withdrew the board and socket so I could have a look underneath and
> ? see what was going on. I was mighty surprised to see that although the
> ? PCB had all the right pads and holes for a five pin socket, only a 3 pin
> ? was fitted. Two of the wires in the 5 wire ribbon were in fact connected
> ? to nothing other than dead-end tracks. I put it back together, and went
> ? on-line to see if I could find a user manual. When I did, I looked up
> ? the section on controls and connectors, and found this entry :
> ?
> ? "PHONES
> ?
> ? The jack is used for connecting the headphones.
> ? When the headphones are plugged in, the sound will cease to come from
> ? the speakers (except for the English model)."
> ?
> ? WTF is that about ? I could maybe at a pinch understand it if there was
> ? a front panel speaker selector switch such as you see on some amps, like
> ? "OFF, A, B, A+B", but there is no such switch on this, nor any other way
> ? that I can see of disabling the speakers, short of disconnecting them.
> ? What is the point, then, of having a headphone socket at all ? Why would
> ? you design it to take a switched socket, and then exclude one model from
> ? using the feature, effectively rendering the socket pretty much useless
> ? for its intended purpose ? Why in particular exclude the "English" model
> ? ? It's not as though there are any regulations here concerning headphone
> ? sockets, and in fact I don't think that I have ever seen another amp
> ? that didn't switch the speakers when phones were plugged in.
> ?
> ? Because I knew that the owner was not going to believe this either, I
> ? printed off the manual page and highlighted the relevant text, before
> ? returning it to the store that sent it in to me ...
> ?
> ? Arfa
>
> **Sounds like the Pommy hi fi press influence to me. Headphone socket
> switches are not the highest quality method of switching a speaker level
> audio signal available.
That's because they use cheap plastic junk, rather that commercial
> **Sounds like the Pommy hi fi press influence to me. Headphone socket
> switches are not the highest quality method of switching a speaker level
> audio signal available.
grade jacks like these:
http://www.switchcraft.com/Drawings/14b_cd.pdf
I've seen these in equipment that is used daily for decades with no
problems.
Phil Allison
Jan 8, 2013, 7:51:29 PM1/8/13
to
"Michael A. Terrell"
>
> Trevor Wilson wrote:
>
>>
>> **Sounds like the Pommy hi fi press influence to me. Headphone socket
>> switches are not the highest quality method of switching a speaker level
>> audio signal available.
>
>
> That's because they use cheap plastic junk, rather that commercial
> grade jacks like these:
>
> http://www.switchcraft.com/Drawings/14b_cd.pdf
>
> I've seen these in equipment that is used daily for decades with no
> problems.
>
** That sort of stereo jack cannot perform speaker switching on a hi-fi
> Trevor Wilson wrote:
>
>>
>> **Sounds like the Pommy hi fi press influence to me. Headphone socket
>> switches are not the highest quality method of switching a speaker level
>> audio signal available.
>
>
> That's because they use cheap plastic junk, rather that commercial
> grade jacks like these:
>
> http://www.switchcraft.com/Drawings/14b_cd.pdf
>
> I've seen these in equipment that is used daily for decades with no
> problems.
>
amplifer.
You need ones that have a pair of independent contacts.
..... Phil
William Sommerwerck
Jan 8, 2013, 8:12:38 PM1/8/13
to
>> http://www.switchcraft.com/Drawings/14b_cd.pdf
> That sort of stereo jack cannot perform speaker switching
> on a hi-fi amplifier.
Sure it can. It's just not a good idea. You don't want to run the amp's output
through such a "cheap 'n dirty" "switch".
> You need ones that have a pair of independent contacts.
???
> That sort of stereo jack cannot perform speaker switching
Sure it can. It's just not a good idea. You don't want to run the amp's output
through such a "cheap 'n dirty" "switch".
> You need ones that have a pair of independent contacts.
Arfa Daily
Jan 8, 2013, 9:09:49 PM1/8/13
to
>>
>>Arfa
>
> I have seen lots of Japanese and some other amplifiers that do not have
> speaker cutouts on the headphone jack; but _ALL_ of them had proper
> speaker switches of some sort.
>
> YMMV
>
> ?-)
arrangement ...
Arfa
Phil Allison
Jan 9, 2013, 1:42:41 AM1/9/13
to
"William Sommerwanker is getting WORSE "
>
>>> http://www.switchcraft.com/Drawings/14b_cd.pdf
>
>> That sort of stereo jack cannot perform speaker switching
>> on a hi-fi amplifier.
>
> Sure it can.
** The only way such a jack could perform speaker switching is if the amp's
>>> http://www.switchcraft.com/Drawings/14b_cd.pdf
>
>> That sort of stereo jack cannot perform speaker switching
>> on a hi-fi amplifier.
>
> Sure it can.
output were connected DIRECT to the headphone contacts - something no
sane amp maker would ever do.
>> You need ones that have a pair of independent contacts.
>
> ???
.... Phil
Michael A. Terrell
Jan 9, 2013, 2:12:36 AM1/9/13
to
Phil Allison wrote:
>
> "Michael A. Terrell"
> ?
> ? Trevor Wilson wrote:
> ?
> ??
> ?? **Sounds like the Pommy hi fi press influence to me. Headphone socket
> ?? switches are not the highest quality method of switching a speaker level
> ?? audio signal available.
> ?
> ?
> ? That's because they use cheap plastic junk, rather that commercial
> ? grade jacks like these:
> ?
> ? http://www.switchcraft.com/Drawings/14b_cd.pdf
> ?
> ? I've seen these in equipment that is used daily for decades with no
> ? problems.
> ?
>
> ** That sort of stereo jack cannot perform speaker switching on a hi-fi
> amplifer.
>
> You need ones that have a pair of independent contacts.
They make those, as well. I was pointing out the construction of the
> ** That sort of stereo jack cannot perform speaker switching on a hi-fi
> amplifer.
>
> You need ones that have a pair of independent contacts.
jack. Their long frame series have additional switches. They are the
same grade that were used in telephone switchboards & audio patch panels
in studios. The point is that they would ad $10 to $10 to the retail
price of the units.
As far as putting resistors in series with the 'cans', it's also
possible to use the extra switches to reduce the drive to the amplifier.
Phil
Jan 9, 2013, 5:32:42 AM1/9/13
to
at will? Best of both worlds.
Gareth Magennis
Jan 9, 2013, 5:05:21 PM1/9/13
to
"William Sommerwerck" wrote in message news:kcig68$59c$1...@dont-email.me...
Gareth.
Michael A. Terrell
Jan 9, 2013, 5:26:01 PM1/9/13
to
reduce the drive. I recall a lot of 180 Ohm resistors on the back of
headphone jacks.
Gareth Magennis
Jan 9, 2013, 6:51:45 PM1/9/13
to
"Michael A. Terrell" wrote in message
news:Jf-dneBblu8Wc3DN...@earthlink.com...
the amplifiers power, or not, via its puny switch to the speakers.
What you really need is a pair of independent contacts in the headphone
socket that makes a circuit when a headphone jack is inserted.
This pair of contacts will then remotely switch the speakers off.
These sockets do actually exist.
Gareth.
Michael A. Terrell
Jan 9, 2013, 8:02:56 PM1/9/13
to
Mark Zacharias
Jan 9, 2013, 8:39:43 PM1/9/13
to
"Gareth Magennis" <gareth....@ntlworld.com> wrote in message
news:NRlHs.1944$k04...@fx20.fr7...
The late model Denon's I've seen use a switch in the headphone jack to
control the speaker relays.
Mark Z.
news:NRlHs.1944$k04...@fx20.fr7...
control the speaker relays.
Mark Z.
Phil Allison
Jan 10, 2013, 2:04:30 AM1/10/13
to
"Gareth Magennis"
>
>> You need ones that have a pair of independent contacts.
>
> ???
>
> Presumably to switch a remote relay.
>
** Not at all.
>> You need ones that have a pair of independent contacts.
>
> ???
>
> Presumably to switch a remote relay.
>
These stereo jacks have two sets of isolated, NC contacts that will do the
job just fine with amplifiers up to say 80 wpc.
See items 3 & 4 on this page:
http://www.minute-man.com/acatalog/1_4__Stereo_Jacks.html
.... Phil
Arfa Daily
Jan 10, 2013, 8:09:44 PM1/10/13
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The system of speaker switching that you are suggesting, is often used on
home cinema systems or AV amps where there are 6 channels to be switched
off. For instance, my Sony HCD - S800 home cinema unit that I use for
optical decoding and surround processing on my TV, has an independent set of
contacts on it that tell the system control micro that headphones have been
jacked in. It responds by cutting off the six speaker protection relays on
the ends of the amps. The actual stereo signal for the headphones is derived
from an independent small amplifier, with a power output more appropriate to
driving them.
Arfa
home cinema systems or AV amps where there are 6 channels to be switched
off. For instance, my Sony HCD - S800 home cinema unit that I use for
optical decoding and surround processing on my TV, has an independent set of
contacts on it that tell the system control micro that headphones have been
jacked in. It responds by cutting off the six speaker protection relays on
the ends of the amps. The actual stereo signal for the headphones is derived
from an independent small amplifier, with a power output more appropriate to
driving them.
Arfa
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