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searching better alternative for LM386

T

Tom

Jan 1, 1970
0
Everyone,

In my design I need to drive headphones with nominally 10 ohm impedance
with an audio signal. The supply for the audio is +12V single supply
(this is created from the main 2.5V-3.3V battery supply using a DC/DC
converter). The output swing does not need to be all the way to the
rail, something like 7..8V peak-peak is acceptable. The input signal is
0..2.5V.

The signals are synthesized sine waves and tone bursts coming from a
DAC, with frequencies from 250Hz to 1kHz. Not music or speech.

Important is that the quiescent power consumption is low (<10 mA if
possible). A shutdown input would be nice but not essential (I can shut
down the DC/DC). Distortion is not so important for this application,
obviously within some reasonable limits (the sine wave shouldn't end up
as something close to a triangle or square wave). Several % THD is
perfectly acceptable.

Important for this application is that the gain of the amplifier is low
to keep a decent signal to noise ratio. If the gain is too high I would
have to attenuate the 0..2.5V DAC signal too much on the input, causing
a penalty in signal to noise ratio (especially at small signal
amplitudes). Ideally the gain would be 4..5.

Currently I am using the LM386, with a gain of 9, which is the minimum
stable gain (by tying a 10K resistor from pin 1 to pin 5). It has low
quiescent power consumption (4mA) and sufficient output swing and
drive, as well as low distortion. However it has one huge disadvantage:
the noise is WAY too high. Even if I short the input pins, the output
noise is VERY audible in the headphones (it sounds white). The noise is
coming from the LM386 and not elsewhere in the circuit, because if I
attenuate the LM386 output, the noise attenuates also (but the signal
also of course).
The LM386 datasheet conveniently does not seem to have any mention of
noise (non-)performance at all!

So, basically I'm looking for a better audio amp, similar to the LM386
but with lower noise. I have found several amps with quite low noise
but either they have too much gain (e.g. 40 dB) or they cannot drive a
10R load. It should also be compact (SMD preferred, but a small DIL
package is also acceptable) and as mentioned with a low quiescent power
consumption. A buffer amp (gain 1) would also be OK, then I will simply
do the required x4..x5 gain in a separate low-power amp stage before.
Does anybody have any suggestions?

greetings,
Tom
 
I

ian field

Jan 1, 1970
0
John Popelish said:
I think you may have jumped to an invalid conclusion. I would say that
the noise you hear is passing through the LM386, but not necessarily being
generated by it. Have you done a listen using a battery as a power
supply?

Check out the National Semiconductor "Boomer" range of amp chips, many are
designed specifically for headphones and include class-D designs and ones
with built in supply rail boosters.
 
P

Phil Allison

Jan 1, 1970
0
** Groper CRIMINAL NIGHTMARE Alert !!


In my design I need to drive headphones with nominally 10 ohm impedance


** What the HELL are they ?

Rejects from Noah's Ark - by any chance ???

Headphones with such low impedance have not been generally on sale in
decades.


The output swing does not need to be all the way to the
rail, something like 7..8V peak-peak is acceptable.


** YOU are completely INSANE !!

With 10 ohm headphones, an input power level like that is LETHAL to the
wearer !!!!


The signals are synthesized sine waves and tone bursts coming from a
DAC, with frequencies from 250Hz to 1kHz. Not music or speech.


** The keep the damn power level in the few milliwatt region

- you FUCKING IDIOT !!

Have you NO FUCKING idea how many dB SPL you are generating !!!!!!!



Currently I am using the LM386, with a gain of 9, which is the minimum
stable gain (by tying a 10K resistor from pin 1 to pin 5). It has low
quiescent power consumption (4mA) and sufficient output swing and
drive, as well as low distortion. However it has one huge disadvantage:
the noise is WAY too high. Even if I short the input pins, the output
noise is VERY audible in the headphones (it sounds white).


** That is complete PROOF of my earlier comments.


YOU are a ABSOLUTE fucking IDIOT who is about to DESTROY some innocent
person's PRECIOUS hearing for the rest of their life !!!

Shooting YOU is TOO damn good for YOU !!!

ASININE FUCKWITS like YOU ought to be BOILED in oil !!!!


Does anybody have any suggestions?


** Yes ..... I fucking do.


The Belgium Police should be notified of your exact whereabouts and what
you are up to.

They should then charge YOU with attempted malicious injury.

Plus give you a MASSIVE boot up your fat stupid ARSE !!!!





........ Phil
 
P

Phil Allison

Jan 1, 1970
0
"John Popelish"
I think you may have jumped to an invalid conclusion. I would say that
the noise you hear is passing through the LM386, but not necessarily being
generated by it.


** Nope - he is correct.

He simply has no idea how dangerous what he is doing is.

Connect some 8 ohm phones DIRECT to a power amp anytime to see the issue.





........ Phil
 
J

John Popelish

Jan 1, 1970
0
Tom said:
Everyone,

In my design I need to drive headphones with nominally 10 ohm impedance
with an audio signal. The supply for the audio is +12V single supply
(this is created from the main 2.5V-3.3V battery supply using a DC/DC
converter). The output swing does not need to be all the way to the
rail, something like 7..8V peak-peak is acceptable. The input signal is
0..2.5V.

The signals are synthesized sine waves and tone bursts coming from a
DAC, with frequencies from 250Hz to 1kHz. Not music or speech.

Important is that the quiescent power consumption is low (<10 mA if
possible). A shutdown input would be nice but not essential (I can shut
down the DC/DC). Distortion is not so important for this application,
obviously within some reasonable limits (the sine wave shouldn't end up
as something close to a triangle or square wave). Several % THD is
perfectly acceptable.

Important for this application is that the gain of the amplifier is low
to keep a decent signal to noise ratio. If the gain is too high I would
have to attenuate the 0..2.5V DAC signal too much on the input, causing
a penalty in signal to noise ratio (especially at small signal
amplitudes). Ideally the gain would be 4..5.

Currently I am using the LM386, with a gain of 9, which is the minimum
stable gain (by tying a 10K resistor from pin 1 to pin 5). It has low
quiescent power consumption (4mA) and sufficient output swing and
drive, as well as low distortion. However it has one huge disadvantage:
the noise is WAY too high. Even if I short the input pins, the output
noise is VERY audible in the headphones (it sounds white). The noise is
coming from the LM386 and not elsewhere in the circuit, because if I
attenuate the LM386 output, the noise attenuates also (but the signal
also of course).
The LM386 datasheet conveniently does not seem to have any mention of
noise (non-)performance at all!

So, basically I'm looking for a better audio amp, similar to the LM386
but with lower noise. I have found several amps with quite low noise
but either they have too much gain (e.g. 40 dB) or they cannot drive a
10R load. It should also be compact (SMD preferred, but a small DIL
package is also acceptable) and as mentioned with a low quiescent power
consumption. A buffer amp (gain 1) would also be OK, then I will simply
do the required x4..x5 gain in a separate low-power amp stage before.
Does anybody have any suggestions?

I think you may have jumped to an invalid conclusion. I
would say that the noise you hear is passing through the
LM386, but not necessarily being generated by it. Have you
done a listen using a battery as a power supply?
 
I

ian field

Jan 1, 1970
0
Phil Allison said:
** Groper CRIMINAL NIGHTMARE Alert !!





** What the HELL are they ?

Rejects from Noah's Ark - by any chance ???

Headphones with such low impedance have not been generally on sale in
decades.





** YOU are completely INSANE !!

With 10 ohm headphones, an input power level like that is LETHAL to the
wearer !!!!





** The keep the damn power level in the few milliwatt region

- you FUCKING IDIOT !!

Have you NO FUCKING idea how many dB SPL you are generating !!!!!!!






** That is complete PROOF of my earlier comments.


YOU are a ABSOLUTE fucking IDIOT who is about to DESTROY some innocent
person's PRECIOUS hearing for the rest of their life !!!

Shooting YOU is TOO damn good for YOU !!!

ASININE FUCKWITS like YOU ought to be BOILED in oil !!!!





** Yes ..... I fucking do.


The Belgium Police should be notified of your exact whereabouts and what
you are up to.

They should then charge YOU with attempted malicious injury.

Plus give you a MASSIVE boot up your fat stupid ARSE !!!!





....... Phil

Feeling better now?!!!
 
J

James Beck

Jan 1, 1970
0
Maybe he needs to plug a clock radio into it.
 
D

D from BC

Jan 1, 1970
0
"John Popelish"



** Nope - he is correct.

He simply has no idea how dangerous what he is doing is.

Connect some 8 ohm phones DIRECT to a power amp anytime to see the issue.





....... Phil

Zobel network?
D from BC
 
M

martin griffith

Jan 1, 1970
0
Everyone,

In my design I need to drive headphones with nominally 10 ohm impedance
with an audio signal. The supply for the audio is +12V single supply
(this is created from the main 2.5V-3.3V battery supply using a DC/DC
converter). The output swing does not need to be all the way to the
rail, something like 7..8V peak-peak is acceptable. The input signal is
0..2.5V.

The signals are synthesized sine waves and tone bursts coming from a
DAC, with frequencies from 250Hz to 1kHz. Not music or speech.

Important is that the quiescent power consumption is low (<10 mA if
possible). A shutdown input would be nice but not essential (I can shut
down the DC/DC). Distortion is not so important for this application,
obviously within some reasonable limits (the sine wave shouldn't end up
as something close to a triangle or square wave). Several % THD is
perfectly acceptable.

Important for this application is that the gain of the amplifier is low
to keep a decent signal to noise ratio. If the gain is too high I would
have to attenuate the 0..2.5V DAC signal too much on the input, causing
a penalty in signal to noise ratio (especially at small signal
amplitudes). Ideally the gain would be 4..5.

Currently I am using the LM386, with a gain of 9, which is the minimum
stable gain (by tying a 10K resistor from pin 1 to pin 5). It has low
quiescent power consumption (4mA) and sufficient output swing and
drive, as well as low distortion. However it has one huge disadvantage:
the noise is WAY too high. Even if I short the input pins, the output
noise is VERY audible in the headphones (it sounds white). The noise is
coming from the LM386 and not elsewhere in the circuit, because if I
attenuate the LM386 output, the noise attenuates also (but the signal
also of course).
The LM386 datasheet conveniently does not seem to have any mention of
noise (non-)performance at all!

So, basically I'm looking for a better audio amp, similar to the LM386
but with lower noise. I have found several amps with quite low noise
but either they have too much gain (e.g. 40 dB) or they cannot drive a
10R load. It should also be compact (SMD preferred, but a small DIL
package is also acceptable) and as mentioned with a low quiescent power
consumption. A buffer amp (gain 1) would also be OK, then I will simply
do the required x4..x5 gain in a separate low-power amp stage before.
Does anybody have any suggestions?

greetings,
Tom
have a look at the LT1010 from linear, specificaly P.14 in the data
sheet
You could possibly use the discrete equivalent, with a "normal" opamp
in front. Of course you would have to mash it up for single rail
working, maybe


martin
 
A

Adrian Jansen

Jan 1, 1970
0
John said:
I think you may have jumped to an invalid conclusion. I would say that
the noise you hear is passing through the LM386, but not necessarily
being generated by it. Have you done a listen using a battery as a
power supply?

I use a similar setup with LM386, and never heard any 'white' noise.
Are you certain it comes from the LM386 ?
They are good at picking up power supply noise.

--
Regards,

Adrian Jansen adrianjansen at internode dot on dot net
Design Engineer J & K Micro Systems
Microcomputer solutions for industrial control
Note reply address is invalid, convert address above to machine form.
 
P

Phil Allison

Jan 1, 1970
0
"Adrian Jansen"
I use a similar setup with LM386, and never heard any 'white' noise. Are
you certain it comes from the LM386 ?


** But YOU did not use 8 or 10 ohm headphones.

If you did, you will hear background hiss.




........ Phil
 
M

MassiveProng

Jan 1, 1970
0
** Groper CRIMINAL NIGHTMARE Alert !!





** What the HELL are they ?

Rejects from Noah's Ark - by any chance ???

Headphones with such low impedance have not been generally on sale in
decades.


As if a dipshit that makes post title changes they way your retarded
ass does would even know.
 
M

MassiveProng

Jan 1, 1970
0
With 10 ohm headphones, an input power level like that is LETHAL to the
wearer !!!!
There are no "lethal" headphones, retard. Though someone should
coat something you touch with curare, or the haitian zombie powder, in
high dosage.
 
P

Phil Allison

Jan 1, 1970
0
"MassiveProng"



** The heading says it all.......





........ Phil
 
T

Tom

Jan 1, 1970
0
Phil,
Headphones with such low impedance have not been generally on sale in
decades.

These are special in-ear phones for use in a medical setting to use
diagnosing the balance organs in your ear. The low impedance allows
high short-time power levels with a relatively low supply voltage
(12V).
With 10 ohm headphones, an input power level like that is LETHAL to the
wearer !!!!

I never said I would apply a constant sine wave with this power. Just a
short toneburst of, for example, 5 cycles long, once every 200
milliseconds or so.
Have you NO FUCKING idea how many dB SPL you are generating !!!!!!!

Yes I have. I NEED to generate something in the order of 150 dB SPL
briefly during these tonebursts (at the maximum power setting,
obviously in most cases (healthy people etc.) the required power will
be much lower).

I am designing an application to specifications from the medical
doctors here. Please don't jump to conclusions about my criminal
intentions are stupidity without knowing anything about my application.

greetings,
Tom
 
T

Terry Given

Jan 1, 1970
0
Tom said:
Phil,




These are special in-ear phones for use in a medical setting to use
diagnosing the balance organs in your ear. The low impedance allows
high short-time power levels with a relatively low supply voltage
(12V).




I never said I would apply a constant sine wave with this power. Just a
short toneburst of, for example, 5 cycles long, once every 200
milliseconds or so.




Yes I have. I NEED to generate something in the order of 150 dB SPL
briefly during these tonebursts (at the maximum power setting,
obviously in most cases (healthy people etc.) the required power will
be much lower).

I am designing an application to specifications from the medical
doctors here. Please don't jump to conclusions about my criminal
intentions are stupidity without knowing anything about my application.

greetings,
Tom

Dont think a rational explanation will prevent the abuse. Just ignore
him, he's one of a couple of lunatics at SED that fly off the handle at
the slightest provocation such as, in your case, asking a sensible question.

You will probably get abused further, for failing to disclose every
nuance of your aplication, regardless that its not actually relevant to
the original question.

BTW this is probably the single best debunking of one of PA's rants I
have ever seen! Well Done sir!

Cheers
Terry
 
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