Phil Allison wrote:

How about you try a TL074 - exact same pin out as the LM324 and no
x-over issues.

Will deliver about 20mA ( = 13mW peak ) into a 32ohm ear phone, which
is plenty loud.


I'll give it a try. Thanks.

A mistake that many people make with lo-Z headphones is to run an amp
straight into them and then wonder why there is so much residual noise.

The easiest method is to use a small power amp such as a LM386 or
TDA2003, then put a resistor in series with it - something in the range
330-470R will usually suit. You will probably end up with a far more
acceptable result as the amp is specifically designed to drive audio
rather than just a general purpose amp.



--
Woody

harrogate three at ntlworld dot com

Woody wrote:
A mistake that many people make with lo-Z headphones is to run an amp
straight into them and then wonder why there is so much residual noise.

The easiest method is to use a small power amp such as a LM386 or
TDA2003, then put a resistor in series with it - something in the range
330-470R will usually suit. You will probably end up with a far more
acceptable result as the amp is specifically designed to drive audio
rather than just a general purpose amp.

That's an impressive damping factor.
I wonder how the frequency response of headphones changes when
current-driven
rather than voltage-driven.

--
Eiron.

"Eiron" wrote in message


That's an impressive damping factor.
I wonder how the frequency response of headphones changes
when current-driven rather than voltage-driven.

The impedance curves of headphones are documented on the web, and are
typically pretty non-uniform.

Probably why so many people like dedicated headphone amps, and drive them
from low impedance, low voltage sources.

Woody wrote:
A mistake that many people make with lo-Z headphones is to run an amp
straight into them and then wonder why there is so much residual
noise.
The easiest method is to use a small power amp such as a LM386 or
TDA2003, then put a resistor in series with it - something in the
range 330-470R will usually suit. You will probably end up with a far
more acceptable result as the amp is specifically designed to drive
audio rather than just a general purpose amp.


Yes, I appreciate that a proper audio amp would do the job better. But I had
a spare amp section on the quad op-amp so I thought I would try to use that
before looking at other options.

Woody wrote:

A mistake that many people make with lo-Z headphones is to run an amp
straight into them and then wonder why there is so much residual noise.

The easiest method is to use a small power amp such as a LM386

Oh FFS ! Grow up !

Graham

TonyL wrote:

I want to drive low-z (32 ohm) headphones using op amps.

Then you're screwed if you need any volume. Most op-amps current limit at around
30mA =~ 20mA RMS. That's 13mW.

Graham

TonyL wrote:

I built a prototype using a LM324 that happened to be handy. Result was
gross crossover distortion

The LM324 is world reknowed for that. Why not use an AUDIO op-amp ?

Graham