Re: Strange how-to question(s)
- From: ehsjr <ehsjr@xxxxxxxxxxxxxxxxx>
- Date: Thu, 02 Oct 2008 03:54:44 GMT
Dan Beck wrote:
"Bob Masta" >
Actually, you can do this without a schematic. As
Tom Biasi suggested earlier, you need to tap into
the volume controls. Find the "top" lug (the one
the slider contacts when the volume is at max) and
unsolder the wire(s) going to it. (In this
vintage radio I suspect that this will be a normal
wired connection, not a PC-mount pot.) That wire
is the radio's audio signal, and the now-bare top
lug is the volume control input to the power amp.
If the radio is stereo, then you'd do this for
both channels (dual-ganged pot). You then use a
DPDT switch (SPDT if mono) to switch that top lug
between the orignal wire or the headphone output.
Note that car radios typically have a second
function on the same shaft as the volume (either
tone or balance), so you need to pay attention to
which pot sections are volume... always the inner
knob AFAIK.
Depending on the oufput level from the MP3 player,
you might need to provide extra attenuation there.
Or, if the radio is mono, you might need to add
series resistors from each headphone channel to
the SPDT lug, to sum them together. (Try 10K)
Other than that, this is a conceptually simple
mod, whose difficulty mostly depends on how hard
it is to get at the pot lugs. There may be a lot
of mechanical stuff in the way due to the station
selector, tuning dial, etc.
Best regards,
Hi Bob,
thank you for your input! If I may indulge you with another question that will display my ignorance...
Ok, so now I have my wire coming out of the headphone jack, that I need to splice into the SPDT switch (the radio is mono). I believe that wire will actually consist of two wires in the plug connector. My presumption is I cut off the plug connector, isolate and strip the two wires, splice them together, and solder to one of the posts on the SPDT switch? If they are necessary, where should I insert the resistor(s)?
Regards,
Dan
Below shows MONO (2 wire) out from the MP3 to the radio.
The resistors aren't needed and you do not splice the
two wires in the plug together. One goes to the radio
ground, the other goes to the switch.
Radio SPDT Player
-----------o o--------------------+
o |
| |
/ ====PlUG
\ |
------->/ |
\ |
| |
|
Gnd --------------------------------+
The resistors are needed if you use STEREO out from the
player, and there will be two wires plus ground in the plug.
Radio SPDT Player
-----------o o---+---[R]---------+
o | |
| +---[R]--------- ====PLug
/ |
\ |
------->/ |
\ |
| |
|
Gnd -------------------------------+
Usually, the ground wire is a braided shield around the
other two wires.
Ed
.
- References:
- Re: Strange how-to question(s)
- From: biscuitbecks
- Re: Strange how-to question(s)
- From: Tim Wescott
- Re: Strange how-to question(s)
- From: Bob Masta
- Re: Strange how-to question(s)
- From: Dan Beck
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