Can it be easily done? I don't know how those sockets work, but here's my
I have a pair of panel speakers in my shower which were driven by a built-
in radio/amp which has long since expired. My Cunning Plan is now to
replace this unit with a bluetooth receiver/amp, which will then receive
content from my phone or preferably, from the radio in the bedroom, for
which I've just ordered a little bluetooth transmitter which plugs into its
headphone socket. That should work fine, except that I'll obviously need
to unplug the transmitter every time I want to listen to the radio in the
bedroom, as the 3.5mm headphone jackplug mutes the radio speakers.
Is there a way of easily preventing the muting, without trashing the radio?
I have no use for headphones as such at all.
Normally a mechanical component of the switch. Can you get access to
the inside of the radio and adjust the contacts so that insertion of the
plug does not break the circuit to the internal speaker.
This picture may help
That is a hand wired mono jack. The radio might have the
jack mounted on the printed circuit board. Also, if it is
capable of producing stereo it will have a third contact - a
ring between the earth sleeve and the tip. This will also
have a switched contact.
It will be very important to isentify the correct contacts
to short on the PCB as getting it wrong and connecting an
output to ground can destroy the audio amplifier.
There will be pads on the PCB on both sides of the jack -
two rows of two, if mono, two rows of three for stereo.
The pads furthest from the jack's input will be the ones to
short ACROSS the jack, not along it!
If it is a stereo jack, the centre contacts on both sides
should alse be shorted
However, there can be variations in the connection
arrangements, so remember the old maxim: if in doubt, DON'T!
That very much depends on the radio. If its old school then there is a
mechanical switch operated by the plug, which may or may not be easy to
bypass if you go inside with a good soldering iron and a short bit of wire,
or if its software based then I suspect if its not in the menu, you are
Even if its hardware, it may well be that the speaker load will be such
that the actual voltage when its connected might well be too low for the
blue tooth dongle. You really need a radio with a line out socket. The old
Pure models had this and in that case the line out jack was fixed and the
volume still controlled the speaker. This idea of using the headphone jack
will always be variable output even if you do bypass the switch on the
This newsgroup posting comes to you directly from...
Also, be wary of overloading the device (eg Bluetooth transmitter) if you
set the radio's volume too high. I use FM headphones with my PC and if I set
the PC volume (software slider on Sound icon) too high, the headphone sound
is distorted, even if I turn the headphone volume down. I tend to use the
lowest PC volume and the highest headphone volume - empirically that gives
Thanks, everyone. I haven't received my transmitter yet, so at least
I'll be wanting to check the system works as envisaged before opening up
the radio to mess with the wiring - will post back when I do that!
FWIW I will certainly need to maintain the output as the headphone
socket, since the bluetooth receiver / amp has no controls at all, and I
will therefore be reliant on the radio knobs to adjust the volume.
Thinking about it though, that means that it might be absolutely
necessary to have the radio's speakers turned off when I use the
Bluetooth transmitter, if it turns out that the volume of the two sets of
speakers are wildly mismatched...
Note that the Bluetooth will introduce a significant latency (delay)
into reproduction, so you won't want to be within earshot of both the
direct and the Bluetooth speakers. Or get an extra Bluetooth speaker for
your bedroom and hope they have equal latency.
I'm inclined to think that Bluetooth is significantly deficient as a
means for wireless audio - pairing difficulties, lack of range,
especially through walls, plus the latency - unfortunately analogue
alternatives are rather hard to obtain these days. 863 MHz is available,
but only with headphones AFAIK. FM is a possibility, so you can use a
normal FM tranny as a speaker, but it's hard to obtain a useable
In article <f4-
max email@example.com says...
After a number of attempts to build a stable FM modulator
during the 60s  - all of which proved eminently unstabe
(!) I came across this circuit which proved unconditionally
I built mine on a Printed Circuit board and used a PP3 for
power. Just laying on the bench it was so stable that it was
unbelievable. Although intended to be connected to a
receiver via a cable (it came from a stereo encoder design)
there was nothing connected to it - not even a primitive
Radiation from the coil was sufficient to cover a reasonably
large area. Only if you placed a finger within about half an
inch from the coil could you detune it.
I built another one that just had a fixed 10pF capacitor in
place of the trimmer between collector and emitter of the
transistor and that worked fine as well. Tuning is by
squeezing or stretching the turns of the coil to alter its
You could, of course, build it in a metal tin and fit an
aerial socket. The circuit shows all of the earth
connections being returned to a common point but on my PCB I
simply allowed a generous width for the earth and that
If you fancy making your own PCB you could copy my idea.
First draw out the layout on a sheet of 0.1" graph paper,
keeping the layout as compact as possible. Clean the copper
laminate and emporarily stick the paper to it with sellotape
then use a centre punch or any sharp point to mark the
copper at every connection point.
Draw the track layout using nail varnish - if you can find
black or any dense colour, so much the better as it shows up
well on the polished copper.
The etchant normally used is ferric chloride but dilute
nitric acid might be easier to find
Drill, build and enjoy!
 Where I was working we had two radios and a radiogram
in, all with intermittent faults on FM. In those days, with
only the Light, Home and Third Programmes available, the
daytime fare was abusmal: The Morning Service, Mrs Dale's
Diary, Womans Hour, Listen with Mother and so on.
After a successful modulator was built we had Radio Caroline
on FM - much easier on the easr!
Install the radioplayer app on your phone, or hack the radio possibly
placing the bluetooth module inside pinching internal power as well?
FWIW, I've just seen the following amp on eBay, for bathroom / kitchen
installs. Is your amp similar?
BATHROOM OR KITCHEN WIRELESS BLUETOOTH AMPLIFIER 2 X 4 INCH CEILING
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