Reduce sensitivity of 100K ohm volume potentiometer?

Guest
I have an audio DSP filter for my amateur radio equipment. It uses an LM380 op-amp in the final AF amp stage, using a 100K ohm pot as the volume control. When using a speaker the volume control is fine, but when using headphones, the sensitivity from quiet to really loud is only a small tweak of the volume know.

Anything I can do to reduce this sensitivity for my headphone output?

Larry
 
lagagnon@gmail.com wrote:

I have an audio DSP filter for my amateur radio equipment. It uses an LM380 op-amp in the final AF amp stage, using a 100K ohm pot as the volume control. When using a speaker the volume control is fine, but when using headphones, the sensitivity from quiet to really loud is only a small tweak of the volume know.

Anything I can do to reduce this sensitivity for my headphone output?

Larry
Click to expand...
Have you thought about using a resistor?

Just a thought really.

You could also use a rheostat voltage divider so you
can make adjustments to the range of the divided output for
head phones to match the speaker, but I would go for the
R..


Jamie
 
On Tue, 13 Nov 2012, lagagnon@gmail.com wrote:

I have an audio DSP filter for my amateur radio equipment. It uses an
LM380 op-amp in the final AF amp stage, using a 100K ohm pot as the
volume control. When using a speaker the volume control is fine, but
when using headphones, the sensitivity from quiet to really loud is only
a small tweak of the volume know.

Anything I can do to reduce this sensitivity for my headphone output?

It's always been pretty common to put a resistor between an audio
Click to expand...
amplifier and any headphones. First, it puts a limit on how much can feed
into the headphones (which may not be able to handle as much as a speaker)
but it also acts as an attenuator with the impedance of the headphones.
IN the tube days, this meant that you wouldn't need to keep the volume
control low, where hum generated by the filament in the output amplifier
could dwarf the signal. If the signal is attenuated after the
amplification, you need to turn up the volume which then makes the wanted
signal larger in reference to the hum. This attenuator on the output
would also cause you to raise your volume control, making it work more
like it would with a speaker.


Michael
 
On 11/13/2012 6:28 PM, Michael Black wrote:
On Tue, 13 Nov 2012, lagagnon@gmail.com wrote:

I have an audio DSP filter for my amateur radio equipment. It uses an
LM380 op-amp in the final AF amp stage, using a 100K ohm pot as the
volume control. When using a speaker the volume control is fine, but
when using headphones, the sensitivity from quiet to really loud is
only a small tweak of the volume know.

Anything I can do to reduce this sensitivity for my headphone output?

It's always been pretty common to put a resistor between an audio
amplifier and any headphones. First, it puts a limit on how much can
feed into the headphones (which may not be able to handle as much as a
speaker) but it also acts as an attenuator with the impedance of the
headphones. IN the tube days, this meant that you wouldn't need to keep
the volume control low, where hum generated by the filament in the
output amplifier could dwarf the signal. If the signal is attenuated
after the amplification, you need to turn up the volume which then makes
the wanted signal larger in reference to the hum. This attenuator on
the output would also cause you to raise your volume control, making it
work more like it would with a speaker.


Michael
Click to expand...
I'm with the Jamie and Michael, Put a series resistor in the
headphone path.
Another option put a 10k potentiometer in series with the 100k
and use the 10k as a fine tune adjustment of volume.
Mikek
 
On Wed, 14 Nov 2012 09:12:15 +1000, <lagagnon@gmail.com> wrote:

I have an audio DSP filter for my amateur radio equipment. It uses an
LM380 op-amp in the final AF amp stage, using a 100K ohm pot as the
volume control. When using a speaker the volume control is fine, but
when using headphones, the sensitivity from quiet to really loud is only
a small tweak of the volume know.

Anything I can do to reduce this sensitivity for my headphone output?

Larry
Click to expand...
Check that the pot is in fact a log pot.
 
lagagnon@gmail.com wrote:
I have an audio DSP filter for my amateur radio equipment. It uses an
LM380 op-amp in the final AF amp stage, using a 100K ohm pot as the
volume control. When using a speaker the volume control is fine, but
when using headphones, the sensitivity from quiet to really loud is
only a small tweak of the volume know.

Anything I can do to reduce this sensitivity for my headphone
output?

Larry
Click to expand...
http://www.electronics-tutorials.ws/attenuators/attenuator.html

--
Les Cargill
 
<lagagnon@gmail.com>
I have an audio DSP filter for my amateur radio equipment. It uses an LM380
Click to expand...
op-amp in the final AF amp stage, using a 100K ohm pot as the volume
control. When using a speaker the volume control is fine, but when using
headphones, the sensitivity from quiet to really loud is only a small tweak
of the volume know.

Anything I can do to reduce this sensitivity for my headphone output?

** There needs to be a resistor of about 150 ohms in series with the
headphone jack, this allows for phones of 8 ohms rating through to 600 ohms
to be used without much change in volume.

The volume pot needs to be a " log" or " audio" taper - usually marked
with the letters "C" or "A" after the value in ohms.

Pots marked with a "B" are linear types.


.... Phil
 
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