Inverting vs. Non-Inverting input for audio?

[MRW]

Hello there!

Someone sent me a link to Maxim's Audio Seminar where they claim that I
can learn stuff not found in the textbooks. Anyway, I somehow found out
about the new MAX9722 with DirectDrive. This caught my eye because it
said that I can eliminate huge DC blocking capacitors. Here is a link
to the datasheet:

http://datasheets.maxim-ic.com/en/ds/MAX9722-MAX9722B.pdf

I noticed that most of the circuits they have on the datasheet uses
inverting input as the main input. I'm just curious why. Is there a
sound quality difference between inverting and non-inverting?

I would assume that the non-inverting option would be use so the signal
stays in phase. But again, I don't know too much about audio yet.
Thanks!



--

 

[MRW]

Hello there!

Someone sent me a link to Maxim's Audio Seminar where they claim that
I can learn stuff not found in the textbooks. Anyway, I somehow found
out about the new MAX9722 with DirectDrive. This caught my eye
because it said that I can eliminate huge DC blocking capacitors.
Here is a link to the datasheet:

http://datasheets.maxim-ic.com/en/ds/MAX9722-MAX9722B.pdf

I noticed that most of the circuits they have on the datasheet uses
inverting input as the main input. I'm just curious why. Is there a
sound quality difference between inverting and non-inverting?

I would assume that the non-inverting option would be use so the
signal stays in phase. But again, I don't know too much about audio
yet. Thanks!

I found this recenlty via Google:
http://www.ecircuitcenter.com/Circuits/op_bandwidth1/op_bandwidth1.htm

Very nice, but I have to re-read it again because I wasn't able to
understand some parts.

--

 

[John Larkin]

Hello there!

Someone sent me a link to Maxim's Audio Seminar where they claim that I
can learn stuff not found in the textbooks. Anyway, I somehow found out
about the new MAX9722 with DirectDrive. This caught my eye because it
said that I can eliminate huge DC blocking capacitors. Here is a link
to the datasheet:

http://datasheets.maxim-ic.com/en/ds/MAX9722-MAX9722B.pdf

I noticed that most of the circuits they have on the datasheet uses
inverting input as the main input. I'm just curious why. Is there a
sound quality difference between inverting and non-inverting?

I would assume that the non-inverting option would be use so the signal
stays in phase. But again, I don't know too much about audio yet.
Thanks!

Was it Jim Williams who said "always invert"? Inverting results in
lower distortion because it eliminates common-mode-rejection errors,
which can be bad even in mega-gain opamps.

But realistically, people imagine they can hear tiny amounts of
distortion, and usually can't. Ears, speakers, walls, girlfriends, and
furniture are already massively nonlinear.

John

 

[Eeyore]

Hello there!

Someone sent me a link to Maxim's Audio Seminar where they claim that I
can learn stuff not found in the textbooks.

Hmmm....

I can tell you more about audio than you'd care to know I'd expect !

Anyway, I somehow found out
about the new MAX9722 with DirectDrive. This caught my eye because it
said that I can eliminate huge DC blocking capacitors. Here is a link
to the datasheet:

http://datasheets.maxim-ic.com/en/ds/MAX9722-MAX9722B.pdf

This is simply designed for the unique requirements of low-voltage portable
equipment. It's nothing to do with 'signal purity'. Maxim is hardly a recognised
contender in the high-performance audio field. The advantage of removing
coupling caps here is smaller equipment size.

I noticed that most of the circuits they have on the datasheet uses
inverting input as the main input. I'm just curious why. Is there a
sound quality difference between inverting and non-inverting?

With a perfect op-amp there certainly shouldn't be.

Many, many years ago there was talk of 'common-mode failure' afflicting (the
input stages of ) some op-amps. Remember that audio circuits used the LM741, 748
and even the uA709 back then ! This dates back to the 70s actually. I dare say
there was some truth in this at the time and I used inverting stages myself out
of choice for a while around then.

The reason for this preference for an inverting stage is to do with circuit
topology and why an inverting configuration is 'cleaner' in some respects. You'd
need to get very familiar with the details of negative feedback to see what I'm
driving at here.

I don't feel the need any longer with modern (high performance audio) op-amps to
use that configuration though.

I would assume that the non-inverting option would be use so the signal
stays in phase. But again, I don't know too much about audio yet.

Yes, non-inverting makes sense but certain stages like EQ (read bass and treble
etc) configure most easily around an inverting stage.

One thing that is always true about an inverting stage is that it's often
noisier than an equivalent non-inverting stage due to the thermal noise
contribution of resistors in the signal path.

Graham

 

[Eeyore]

I found this recenlty via Google:
http://www.ecircuitcenter.com/Circuits/op_bandwidth1/op_bandwidth1.htm

Very nice, but I have to re-read it again because I wasn't able to
understand some parts.

Yes, it makes a mountain out of a molehill. I'd avoid paying too much attention
to it.

Graham

 

[Jon Slaughter]

Hmmm....

I can tell you more about audio than you'd care to know I'd expect !

Yeah... cause your the resident god of all electronics(don't be so modest)!

 

[sparky]

Hmmm....

I can tell you more about audio than you'd care to know I'd expect !

Apparently you know a lot more about BS than most of us!

 

[Eeyore]

Was it Jim Williams who said "always invert"? Inverting results in
lower distortion because it eliminates common-mode-rejection errors,
which can be bad even in mega-gain opamps.

I'd like to see justification for that assertion wrt modern opamps.


Graham

 

[Eeyore]

Yeah... cause your the resident god of all electronics(don't be so modest)!

I'm certainly an audio god. There must be precious little I don't know about it
and I'm continuing to research even those bits.

Graham

 

[Eeyore]

Apparently you know a lot more about BS than most of us!

Apparently you know more about making an idiot of yourself publicly than most of
us.

Do please explain why inverting and non-inverting configurations can behave
differently. So far, there's just one poster other than myself who's put his
finger on it.

Graham

 

[[email protected]]

I found this recenlty via Google:http://www.ecircuitcenter.com/Circuits/op_bandwidth1/op_bandwidth1.htm

Very nice, but I have to re-read it again because I wasn't able to
understand some parts.

--

dito

 

[John Fields]

Apparently you know more about making an idiot of yourself publicly than most of
us.

 

[John Larkin]

Funny. He disputed my common-mode note[1], and literally three minutes
later said he's the only other person smart enough to "put his finger
on" the issue.

John

[1] Jim Williams', actually.

 

[John Larkin]

Yeah... cause your the resident god of all electronics(don't be so modest)!

Audio isn't electronics any more than cargo-cult worship is
aerodynamics.

John

 

[cpemma]

Is there a sound quality difference between inverting and non-inverting?

The fact that audiophiles (and non-audiophiles) argue about the merits of
each demonstrates that the audible difference is negligible.

 

[BobG]

=========================================
Usually amplifiers are in phase... the output goes positive when the
input goes positive, but in certain rare circumstances, such as when
listening to the Beatles 'Tomorrow never comes' or 'I am the Walrus'
or any passage with inverted sound effects, using the inverting input
on the opamp causes a subtle psychoacoutic phenomenon to occur that
makes the listener think he hears 'Paul is Dead.... Paul is Dead'

 

[neon]

There is asolute no difference. How can it be the two input points are virtualy the same points. iT CANNOT BE DIFFERENT IF THERE IS THEN x THE GAIN YOU WILL SEE IT IN THE OUTPUT. That why they are called differential amps. the amplify the difference. I also choose inverters when designing amps it is easy to calculate i imagen no other reaon that i see.

 

[sparky]

Apparently you know more about making an idiot of yourself publicly than most of
us.

Do please explain why inverting and non-inverting configurations can behave
differently. So far, there's just one poster other than myself who's put his
finger on it.

Are you sure you did not put your finger IN it ?

 

[neon]

I THINK YOU ARE REFERING TO MY POSTING AND YOU ARE THE IDIOT THERE IS AND I CLAIM ABSOLUTELY NO DIFFERENCE IN WHERE YOU PUT THE INPUT. the only difference is in the output one is an inverter and the other is not, you are the IDIOT i hate people that they think they know while they themself do not understand. You Just read books and look at pictures. I probably forgot more then you will ever know how a about that IDIOT. And your claim that you know audio to me that is like I know DC BIG DEAL. get a life