4 Aug
2004
4 Aug
'04
10:05 a.m.
I do realize that this doesn't really apply here, but I know some of
the electronic geniuses here can help me out...
I have a little Timex clock radio. Works great, except when I want to
fall asleep to the radio, I need to turn it down so as not to disturb my
wife. Problem is, that the volume control isn't sensitive enough at the
low volume I want.
So, my thought is to put a resistor on the positive lead of the
speaker, which (I think) would lower the overall volume output, and give
me a wider range to adjust the volume to a quiet level.
I'm just not sure what size resistor to use, or if that is even the
right way to go. I haven't cracked it open yet, but I'm fairly certain
it's only a single speaker in there, and it's probably a 16 ohm one at
that. Am I on the right track?
--
--- Dave Woyciesjes
--- ICQ# 905818
4 Aug
4 Aug
10:32 a.m.
Clock radio speaker output reduction:
Note that a good number of the smaller clock radios use higher-than-usual
speaker impedances. sometimes upward of 60 ohms: saves output devices
having to handle heavy currents (relatively).
T'were it me, I'd obtain a 500-ohm 'trimmer' pot - the kind that is
meant to go on a printed circuit board, be adjusted once, then left...
500 ohms at 1/4W would be fine - then put it series [one speaker wire goes
to the wiper of the pot, the other goes to one of the 'ends' of the pot]
in one of the the speaker lines (doesn't matter which one) and tweak it
until you have the gain level you like. Pop the cover back on et Voila!
all done. Just get a single-turn one, not the multi-turn type. If you
really want to get fancy, you can put a small switch in the case, and
short out the pot, thus restoring the radio to full volume if desired. If
you could find a suitable volume-control / switch combination, that might
also be a slick way to do this.. but I doubt seriously that a 500-ohm
volume control with integral switch could be found.
The usual cautions about working on/around mains-connected devices
applies, if the clockradio is in fact plugged right into the wall.
Cheers
John
PS: this presupposes you are comfortable with soldering....
10:56 a.m.
>> the other goes
>> to one of the 'ends' of the pot] in one of the the speaker
>> lines (doesn't matter which one)
Assuming it is a linear and not audio taper pot <g>
>> -----Original Message-----
>> From: cctalk-bounces(a)classiccmp.org
>> [mailto:cctalk-bounces@classiccmp.org] On Behalf Of John Lawson
>> Sent: Wednesday, August 04, 2004 3:33 PM
>> To: woyciesjes(a)sbcglobal.net; General Discussion: On-Topic
>> and Off-Topic Posts
>> Subject: Re: OT: Simple electronics question...
>>
>>
>>
>> Clock radio speaker output reduction:
>>
>> Note that a good number of the smaller clock radios use
>> higher-than-usual speaker impedances. sometimes upward of
>> 60 ohms: saves output devices having to handle heavy
>> currents (relatively).
>>
>> T'were it me, I'd obtain a 500-ohm 'trimmer' pot - the
>> kind that is meant to go on a printed circuit board, be
>> adjusted once, then left...
>> 500 ohms at 1/4W would be fine - then put it series [one
>> speaker wire goes to the wiper of the pot, the other goes
>> to one of the 'ends' of the pot] in one of the the speaker
>> lines (doesn't matter which one) and tweak it until you
>> have the gain level you like. Pop the cover back on et Voila!
>> all done. Just get a single-turn one, not the multi-turn
>> type. If you really want to get fancy, you can put a small
>> switch in the case, and short out the pot, thus restoring
>> the radio to full volume if desired. If you could find a
>> suitable volume-control / switch combination, that might
>> also be a slick way to do this.. but I doubt seriously that
>> a 500-ohm volume control with integral switch could be found.
>>
>> The usual cautions about working on/around
>> mains-connected devices applies, if the clockradio is in
>> fact plugged right into the wall.
>>
>>
>> Cheers
>>
>> John
>>
>>
>> PS: this presupposes you are comfortable with soldering....
2:44 p.m.
>> the other goes
>> to one of the 'ends' of the pot] in one of the the speaker
>> lines (doesn't matter which one)
Assuming it is a linear and not audio taper pot <g>
11:05 a.m.
John Lawson wrote:
Clock radio speaker output reduction:
Note that a good number of the smaller clock radios use
higher-than-usual speaker impedances. sometimes upward of 60 ohms: saves
output devices having to handle heavy currents (relatively).
T'were it me, I'd obtain a 500-ohm 'trimmer' pot - the kind that is
meant to go on a printed circuit board, be adjusted once, then left...
500 ohms at 1/4W would be fine - then put it series...
If you really want to get fancy, you can put a small switch in the case,
and short out the pot, thus restoring the radio to full volume if
desired...
Thanks very much. This idea will do just dandy.
PS: this presupposes you are comfortable with
soldering....
I'm by no means an expert, but I ain't afraid of it either.
--
--- Dave Woyciesjes
--- ICQ# 905818
1:03 p.m.
I have a little Timex clock radio. Works great,
except when I want
to fall asleep to the radio, I need to turn it down so as not to
disturb my wife. Problem is, that the volume control isn't sensitive
enough at the low volume I want.
So, my thought is to put a resistor on the positive
lead of the
speaker, which (I think) would lower the overall volume output, and
give me a wider range to adjust the volume to a quiet level.
Well, speakers mostly don't have polarity on their leads. At least not
voice-coil speakers such as you find in "little clock radio"s.
(Switching the leads will reverse the direction of voice-coil movement
for a given current - but that difference is approximately inaudible.)
You could do that. But you might be better off frobbing the
volume-control circuit itself. The volume control is projbably a pot
with one side grounded, one side driven, and the variable tap taken to
drive further electronics. Inserting a resistor in series with the
non-grounded side will do something like what you want.
Either of these approaches runs a risk of creating impedance mismatches
between the driving circuit and the driven thing. Which way introduces
less distortion depends on the circuit - though I must confess that I
would expect the distortion introduced by this mismatch to be far less
than you get from other causes in most clock radios.
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5 Aug
5 Aug
1:41 p.m.
You could do that. But you might be better off frobbing the
volume-control circuit itself. The volume control is projbably a pot
with one side grounded, one side driven, and the variable tap taken to
drive further electronics. Inserting a resistor in series with the
non-grounded side will do something like what you want.
I would have thought that placing a low value pot. in series with the
grounded side - say 100 ohm to start with , and turn the radio volume
control to minimum , then wind up your 100 ohm to get the level you want.
The problem you have is at the bottom end of the range of the control - this
would effectively expand that control and not make too much difference to
the impedance of the circuit.
I think you will find that this will work and you won't need to switch it
out as it's effect is minimal.
Geoff.
Either of these approaches runs a risk of creating impedance mismatches
between the driving circuit and the driven thing. Which way introduces
less distortion depends on the circuit - though I must confess that I
would expect the distortion introduced by this mismatch to be far less
than you get from other causes in most clock radios.
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4 Aug
4 Aug
2:41 p.m.
I do realize that this doesn't really apply here, but I know some of
the electronic geniuses here can help me out...
Not a genius, but anyway...
I have a little Timex clock radio. Works great,
except when I want to
fall asleep to the radio, I need to turn it down so as not to disturb my
wife. Problem is, that the volume control isn't sensitive enough at the
low volume I want.
So, my thought is to put a resistor on the positive lead of the
speaker, which (I think) would lower the overall volume output, and give
me a wider range to adjust the volume to a quiet level.
That would work, I think, but what I'd do is find the 'top' end of the
volume control pot (not the silder, not the end that goes to earth), and
stick a resistor in series with it. Something of about the same
resistance as the control would probably be a good start.
I'm just not sure what size resistor to use, or
if that is even the
right way to go. I haven't cracked it open yet, but I'm fairly certain
it's only a single speaker in there, and it's probably a 16 ohm one at
that. Am I on the right track?
More likely to be 8 ohms. If you want to try a resistor in series with
the speaker (and it doens't matter which wire you insert it in, of
course), try something of a few 10's of ohms to start with.
[YEs, I know that mis-natching an output stage to its load can be a bad
thing, but I don't think it'll do any harm at all in this sort of device]
-tony
7272
days inactive
7273
days old
8 comments
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participants (6)
-
ard＠p850ug1.demon.co.uk -
dvcorbin＠optonline.net -
geoffreythomas＠onetel.com -
jpl15＠panix.com -
mouse＠Rodents.Montreal.QC.CA -
woyciesjes＠sbcglobal.net