Opamp vs audio amplifier??

Thread Starter

abdulwahab.hajar

Joined Jun 14, 2016
93
What would the difference between an audio amplifier and an opamp be exactly?
don't they both amplify the signal's amplitude (voltage)?
I want to amplify a signal from an electret microphone to 5V, I believe an opamp should be sufficient right...... Then what's so special about an audio opamp.

Keep in mind that my signal only contains frequencies up to 1760Hz.

Thank you
 

OBW0549

Joined Mar 2, 2015
3,566
An audio amplifier chip, such as an LM386, is capable of driving high currents into low-resistance loads, such as a loudspeaker. Most opamps can supply only a few tens of milliamps.
 

shteii01

Joined Feb 19, 2010
4,644
To start with.
Audio is defined as frequencies from 20 Hz to 20 kHz.
So.
If you have op amp that only goes to 10 kHz... you safely say that it is not audio amplifier.
Also. Since you don't need hundredth of MHz, those op amps, while nice, are not needed.

1.760 kHz seems too low to me to be audio. Old analog phones used about 7-8 kHz. Most people can not really hear beyond 17 kHz.
Are you sure 1.760 kHz is right? Maybe you are missing a zero? 17.60 kHz would have made sense to me.
 

wayneh

Joined Sep 9, 2010
17,496
Old analog phones used about 7-8 kHz. Most people can not really hear beyond 17 kHz.
I think that's off. Most people by middle age can't hear much above 10kHz. Human voice and most music is around 1kHz. I could see a phone going to 5kHz to make consonants clear, but most of the content is well below. The 1.76kHz noted is a perfectly reasonable audio frequency.
 

Thread Starter

abdulwahab.hajar

Joined Jun 14, 2016
93
To start with.
Audio is defined as frequencies from 20 Hz to 20 kHz.
So.
If you have op amp that only goes to 10 kHz... you safely say that it is not audio amplifier.
Also. Since you don't need hundredth of MHz, those op amps, while nice, are not needed.

1.760 kHz seems too low to me to be audio. Old analog phones used about 7-8 kHz. Most people can not really hear beyond 17 kHz.
Are you sure 1.760 kHz is right? Maybe you are missing a zero? 17.60 kHz would have made sense to me.
it's audio for sure, I want to analyze audio signals from 880Hz to 1760Hz..... Namely guitar notes
 

Thread Starter

abdulwahab.hajar

Joined Jun 14, 2016
93
An audio amplifier chip, such as an LM386, is capable of driving high currents into low-resistance loads, such as a loudspeaker. Most opamps can supply only a few tens of milliamps.
The signal won't be going into a loudspeaker, I want it to go through a filter and then a microprocessor.... I need the voltage before it reaches the filter to be 5V...... from what you said I understand that an audio amplifier is not necessary for me and that an opamp would serve just fine for voltage amplification.
However, would an audio amplifier lower the circuit noise thus making my signal clearer??
and audio amplifiers also amplify power thus also amplifying my voltage giving my audio amplifier an edge over the opamp right?

Thank you
 

MrChips

Joined Oct 2, 2009
30,720
The signal won't be going into a loudspeaker, I want it to go through a filter and then a microprocessor.... I need the voltage before it reaches the filter to be 5V...... from what you said I understand that an audio amplifier is not necessary for me and that an opamp would serve just fine for voltage amplification.
However, would an audio amplifier lower the circuit noise thus making my signal clearer??
and audio amplifiers also amplify power thus also amplifying my voltage giving my audio amplifier an edge over the opamp right?

Thank you
If you want to increase the voltage of the audio signal, use an opamp.
Neither will reduce circuit noise.
 

OBW0549

Joined Mar 2, 2015
3,566
The signal won't be going into a loudspeaker, I want it to go through a filter and then a microprocessor.... I need the voltage before it reaches the filter to be 5V...... from what you said I understand that an audio amplifier is not necessary for me and that an opamp would serve just fine for voltage amplification.
However, would an audio amplifier lower the circuit noise thus making my signal clearer??
and audio amplifiers also amplify power thus also amplifying my voltage giving my audio amplifier an edge over the opamp right?
OK, I misunderstood; I thought you were wanting to power a speaker. Since you aren't, and you are concerned about noise, I'd suggest a good low-noise opamp such as the NE5532, which is often used for audio work.
 

AnalogKid

Joined Aug 1, 2013
10,988
Old analog phones used about 7-8 kHz.
POTS has a nominal bandwidth of 3.3 or 3.4 kHz (depending on who you ask), usually rounded up to 4 kHz for signal system discussions, and down to 3 kHz for actual performance discussions. The public switched telephone network (PSTN) samples this at 8 kHz/8 bits for a 64 kbps digital channel called DS0.

ak
 

WBahn

Joined Mar 31, 2012
29,979
To start with.
Audio is defined as frequencies from 20 Hz to 20 kHz.
So.
If you have op amp that only goes to 10 kHz... you safely say that it is not audio amplifier.
Also. Since you don't need hundredth of MHz, those op amps, while nice, are not needed.

1.760 kHz seems too low to me to be audio. Old analog phones used about 7-8 kHz. Most people can not really hear beyond 17 kHz.
Are you sure 1.760 kHz is right? Maybe you are missing a zero? 17.60 kHz would have made sense to me.
I believe the old analog phones had a bandwidth of 3 kHz, or a bit more. My hearing is about average for my age and I can't hear much above 10 kHz. Yet I don't seem to notice the loss when I listen to the same music CDs that really impressed me with the clarity and range back when I was 21. Could be faulty memory, but that leads me to believe that most music doesn't have a lot of content above somewhere around 10 kHz (or possibly even lower). I know that I can still easily hear the highest note on a standard piano. So what content that music has above that is almost certainly in higher harmonics that contributes to the finer distinctions in the instruments and that most people don't really notice when they are missing.
 

wayneh

Joined Sep 9, 2010
17,496
Loss of high frequency hearing becomes a problem for the elderly when they cannot distinguish consonants in speech. They have to turn up the TV to make out what the actors are saying. The rest is loud, even to them. I think with music, they don't really notice the less-than-crisp fidelity. You can still enjoy it without feeling like you're missing something.
 

MrChips

Joined Oct 2, 2009
30,720
POTS has a nominal bandwidth of 3.3 or 3.4 kHz (depending on who you ask), usually rounded up to 4 kHz for signal system discussions, and down to 3 kHz for actual performance discussions. The public switched telephone network (PSTN) samples this at 8 kHz/8 bits for a 64 kbps digital channel called DS0.

ak
Correct. Plain Old Telephone Service (POTS) bandwidth is 3.4kHz.
 
Loss of high frequency hearing becomes a problem for the elderly when they cannot distinguish consonants in speech. They have to turn up the TV to make out what the actors are saying. The rest is loud, even to them. I think with music, they don't really notice the less-than-crisp fidelity. You can still enjoy it without feeling like you're missing something.
I left most of my high frequency hearing over in Vietnam when I was 18-19 years old. I am now 68 and my hearing has gone even more, perhaps it was 25 years on the PD with pistol practice and qualifications even with hearing protection. At any rate the new breed of rechargeable hearing aides have really made things come back for me, thanks to the VA I received another nice set last month. Using some good noise canceling headphones I can once again enjoy CCR and 3 Dog Night, in fact I was listening to them again this afternoon as my young grandsons were fighting over their Christmas gifts in the living room where I sat, my children and my good wife were loudly playing pinochle in the next room very loudly, man 3 Dog Night never sounded so good, it was all I could hear, thank God.
 

Wolframore

Joined Jan 21, 2019
2,609
Here are the harmonics and frequencies for a plucked E4 (open e). Notice all the harmonics. These harmonics will also generate difference tones and other effects as they bounce and reflect in and out of phase. Unless you’re listening with headphones the harmonics affect the fundamentals. If you cut everything off after 2k it would no longer sound the same. Your tone is colored by harmonics. this is why pro audio equipment will go beyond the hearing bandwidth And why 24 bit 196k capable of 96 kHz sounds so real.

1577190977548.png
 

Audioguru again

Joined Oct 21, 2019
6,674
The problem in this thread is that the question asked about an audio amplifier or an opamp without saying No Loudspeaker and without asking about using a noisy ordinary opamp or a low noise audio opamp.
The circuit is called an audio preamp.

Also, not said is why the bandwidth is so narrow, cutting all high audio frequencies. Maybe it is sending tones, not voices and not music.

Plain Old Telephone bandwidth? I measured a round trip on a telephone call transmitting on one telephone line and receiving on the next telephone line at work. The central office was about 3 miles away so the round trip had 6 miles of capacitance cutting high frequencies. -3dB was at only 2.5kHz so I called Bell and complained. Bell said it was normal and was well within the -15dB(!) that is their limit. That is why most phrases on an old telephone call were, "What did you say?".

I am 74 years old and I have "normal for my age" high frequency hearing loss. My hearing aids make up for most of the loss and sound great.
 

SamR

Joined Mar 19, 2019
5,031
I built a "sensitive audio detector" and hooked it up to my signal generator. Yes I am damn near deaf especially in my left ear on low freq. Quick way to find out just how bad you are. And I don't want to have to use hearing aids much to the wife's displeasure.
 

Audioguru again

Joined Oct 21, 2019
6,674
My hearing aids have 4 settings that are selected sequentially by a button on either one:

1) Automatic mode with AGC and noise reduction which I use in malls, restaurants and walking beside noisy traffic. If a voice is heard by one mic or both front and rear mics on one side then that mic plays in both ears.
2) Music mode with nothing changing the sounds. All 4 mics are continuously turned on.
3) Muting mode which I use to shut up barking, nagging and crying babies.
4) Extra sensitivity mode which I use for snooping about what other people are talking about, hey those pretty girls over there are talking about me!

A hearing aid detects a magnet in a phone's handset then plays the telephone sounds in both ears.
The zinc-air button batteries last for 2 weeks (turned off each night) and are inexpensive at Costco.
 
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