Hello,

What precisely is recording volume on the "line in" of
a sound card?

Is it true that the "line in" of a sound card does not
have a preamp?

This is confusing to me. Why have a recording volume
on the sound card at all if the sound coming into the
card is already line level?

Here's the essence of my confusion: Does the sound
actually get amplified by the recording volume on
the sound card in the same way that a pre-amp amplifies
sound? If so, can the sound be distorted by the recording
volume on the line in?

The "line in" recording volume might make sense to me
if I thought of it as being pure math. I can imagine
the ADC (Analog to Digital Converter) taking the sound
pressure level and converting it to a number. I can
further imagine that number being bumped upwards or downwards
by a mathematical formula.

I don't know what I'm talking here but I'm trying to
figure it all out.

Here's why I ca I want to know how to set sound levels
on my mixer and on my sound card when recording my voice.
Am I better off cranking up the volume on my mixer or am I
better off cranking up the volume on my sound card when
making recordings of my voice?

I'm talking about the "line in." I know not to use the
"mic in" as that would cause the sound card mic pre-amps
to kick in which I understand are not very good.

My sound card is onboard NVIDIA audio on an ASUS a7n266-vm
motherboard. My preamp is a Eurorach UB502 mixer. My mic
is a Sennheiser 835 hand held dynamic mic.

It's clear to me that the sound recordings made with the
NVIDIA onboard sound is not that good. Why? The left
meter gets ahead of the right meter just a little bit
whenever I record silence. This is true even with no cables
plugged into the sound card.

I'm thinking of buying a Turtle Beach Santz Cruz card so that
I can get a reasonably good reproduction of my voice. I'm
doing straight voice recordings with no mixing of any other
sound into the recording.

I'm thinking that maybe I should learn how to set sound levels
on my present card before purchasing a new card. First things
first.

Thanks to all who took the time to read this relatively long
post.

Ed Abbott

"Ed Abbott" wrote in message
om

What precisely is recording volume on the "line in" of
a sound card?

What do you mean by "recording volume"?

Is it true that the "line in" of a sound card does not
have a preamp?

That is true, in general but numerous exceptions exist. Often when a
ordinary PC sound card has a mic input, it is only for business voice work
and unsuitable for audio production. Often it is mono, has a DC voltage
associated with it, and is amplified by a substandard circuit.

This is confusing to me. Why have a recording volume
on the sound card at all if the sound coming into the
card is already line level?

In fact most modern audio interfaces intended for audio production lack
input level controls.

Here's the essence of my confusion: Does the sound
actually get amplified by the recording volume on
the sound card in the same way that a pre-amp amplifies
sound?

Not really. Of course now there is a question of what you mean by "pre-amp".
Do you mean a hi fi home stereo type preamp or a mic preamp?

If so, can the sound be distorted by the recording volume on the line in?

Depending on the circumstances.

The "line in" recording volume might make sense to me
if I thought of it as being pure math. I can imagine
the ADC (Analog to Digital Converter) taking the sound
pressure level and converting it to a number. I can
further imagine that number being bumped upwards or downwards
by a mathematical formula.

This is one of two possible implementations. The other implemntation
controls the gain in analog domain, before digitization. You would have to
provide the make and model of your audio interface to get a good answer to
this question.

I don't know what I'm talking here but I'm trying to
figure it all out.

Keep talking - as in provide us with some answers.

Here's why I ca I want to know how to set sound levels
on my mixer and on my sound card when recording my voice.

That depends.

Obviously, the audio interfaces with no input levels make it easy. You can
only set levels on the mixer.

Some audio interfaces provide optimal performance with the level controls
set all the way up, others with the level controls set in the middle, and
others with the level controls set to the lowest level that still gives an
output.

Am I better off cranking up the volume on my mixer or am I
better off cranking up the volume on my sound card when
making recordings of my voice?

You've got ears, right? What sounds best to you?

I'm talking about the "line in." I know not to use the
"mic in" as that would cause the sound card mic pre-amps
to kick in which I understand are not very good.

You understand correctly.

My sound card is onboard NVIDIA audio on an ASUS a7n266-vm
motherboard. My preamp is a Eurorach UB502 mixer. My mic
is a Sennheiser 835 hand held dynamic mic.

Last time I worked with a Nvidea audio interface, it was not all that good.
I can't remember whether it was one of the ones that provide optimal
performance with the level controls set all the way up, with the level
controls set in the middle, or with the level controls set to the lowest
level that still gives an output. But, I'm sure it was one of the three, and
I'm sure I could figure it out by ear.

It's clear to me that the sound recordings made with the
NVIDIA onboard sound is not that good. Why?

Your procedures, your associated equipment, and the card itself. Pick one,
two or all three as they apply. What mic, what mixer?

The left
meter gets ahead of the right meter just a little bit
whenever I record silence. This is true even with no cables
plugged into the sound card.

Not positively indicative of anything, but perhaps troubling.

I'm thinking of buying a Turtle Beach Santz Cruz card so that
I can get a reasonably good reproduction of my voice.

My recollection is that while it wasn't wonderful hi-fi, the last Nvidia
card wasn't horrible. What is specifically wrong with your voice recordings?
Were you singing or speaking?

I'm doing straight voice recordings with no mixing of any other
sound into the recording.

If I was going to recommend a low cost audio interface, I might recommend
the SoundBlaster USB MP3. It is one of the interfaces that works best with
the input level control set to the lowest setting that still gives sound.

I'm thinking that maybe I should learn how to set sound levels
on my present card before purchasing a new card. First things first.

This is an idea. The boundary conditions are either too noisy, or too
distorted. If you are recording with a visual audio editor (Audacity is good
and free) you can check for distortion because it takes the form of
flat-topping of the waves. Noise looks like little grassy stuff.

Ed Abbott wrote:

What precisely is recording volume on the "line in" of
a sound card?

There is a specification on the card somewhere, saying what voltage input
gives you 0 dBFS. It's different from unit to unit since there is no
real consumer level standard.

Is it true that the "line in" of a sound card does not
have a preamp?

Right. It takes a line input and not a mike input.

This is confusing to me. Why have a recording volume
on the sound card at all if the sound coming into the
card is already line level?

What is line level? Is your line level the same as my line level?
If all instruments made exactly the same level output and every preamp
had exactly the same amount of gain, nothing would be required.

Here's the essence of my confusion: Does the sound
actually get amplified by the recording volume on
the sound card in the same way that a pre-amp amplifies
sound? If so, can the sound be distorted by the recording
volume on the line in?

Yes, you can easily clip the inputs on the card. It's important to watch
the levels you have going in.

Here's why I ca I want to know how to set sound levels
on my mixer and on my sound card when recording my voice.
Am I better off cranking up the volume on my mixer or am I
better off cranking up the volume on my sound card when
making recordings of my voice?

There is a really nice discussion in the FAQ on gain structures in general,
which I think applies to this. On the whole, you want the level of the
signal everywhere in the sound path to be below clipping, never above clipping,
and never so far down that there is a noise issue. This means you need to
bring the level at each stage up so you can see where it clips, then bring
it down again so it doesn't ever do so.

It's clear to me that the sound recordings made with the
NVIDIA onboard sound is not that good. Why? The left
meter gets ahead of the right meter just a little bit
whenever I record silence. This is true even with no cables
plugged into the sound card.

Sure, but how does that correlate with the sound? I would suspect that
your converter aren't very good there, but what can you hear that leads you
to believe that? Ignore the meters and listen.

I'm thinking of buying a Turtle Beach Santz Cruz card so that
I can get a reasonably good reproduction of my voice. I'm
doing straight voice recordings with no mixing of any other
sound into the recording.

I'm thinking that maybe I should learn how to set sound levels
on my present card before purchasing a new card. First things
first.

I would tend to agree, and I think you should also get some monitoring that
allows you to hear what is going on with your card.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

This is an idea. The boundary conditions are either too noisy, or too
distorted. If you are recording with a visual audio editor (Audacity is
good and free) you can check for distortion because it takes the form of
flat-topping of the waves. Noise looks like little grassy stuff.

Hi Arny,

Thanks so much for your reply.

I'm using Goldwave as my tool to record.

I guess that I must be dealing with distortion because the left channel
always has a flat line that can only be manipulated by changing the sound
level on the "line in". If I raise the volume on the sound card, the flat
line grows on the left level meter and if I lower the volume (again, while
recording) the flat line shrinks on the left level meter. This happens
regardless of whether or not I have any audio cables plugged into the card.

In other words, Goldwave records a flat line on the left channel even with
no audio source present.

Is this what you mean by "flat-topping of waves." It doesn't look like
a wave. It looks like a line that does not go away until you add sound
on top of it. In other words, the left channel always has a level even
with no sound source present.

I wonder if I blew out my audio card (the left channel) by putting the
gain up to high on my pre-amp (Behringer UB502 mixer).

Thank you so much for the recommendation of the SoundBlaster USB MP3 as
a sound card. This sounds ideal for my application as I'm not singing,
just speaking. My ideal sound is a voiceover quality sound with no other
audio present. I'm making educational audio CDs.

I've no present need to record anything but my voice.

BTW, I have a memory of turning the volume up way too high on the card and
the mixer in combination and absolutely pegging the meters in Goldwave
while recording. This is why I wonder if I've blown out my card somewhat.

It just seemed like such a bad thing to do at the time. Of course, it was
a mistake.

The recorded sound that comes out of the card is not too terrible. It just
sounds a bit murky to me but maybe I'm being picky.

Ed

There is a really nice discussion in the FAQ on gain structures in
general,
which I think applies to this. On the whole, you want the level of the
signal everywhere in the sound path to be below clipping, never above
clipping,
and never so far down that there is a noise issue. This means you need to
bring the level at each stage up so you can see where it clips, then bring
it down again so it doesn't ever do so.


Hi Scott,

Thanks for your reply.

I've quoted the part of your answer that turned on a light bulb for me.

My question was a little off because my understanding was off. If I
interpret your answer correctly, the way to set levels is to start at
the beginning of the signal path and set levels at each stage to somewhat
below the clipping level.

My Behringer Mixer (UB502) is basically an analog device so I would set
the levels to go into the yellow (six db on the meter) occasionally but to
generally stay in the range at the top of the green (zero db on the
meter). (The volume of my voice is pretty steady.)

Once I'd set the levels on the mixer, I'd set the levels on the sound
card next.

Basically, I'd set the sound card to a level where it never goes as high
as zero db because I'm working with a digital interface.

Sorry to be so pedantic. I'm just trying to repeat back what I may or
may not have rightly understood from what you've said.

Ed

Ed,

You already got great answers from the experts, and I'll just add this
simple recipe:

When recording using a consumer level sound card, set the line input level
to maximum and use whatever is feeding it - a preamp or mixer - to set the
recording level so it gets near zero but never over.

--Ethan

"Ethan Winer" ethanw at ethanwiner dot com wrote:

Ed,

You already got great answers from the experts, and I'll just add this
simple recipe:

When recording using a consumer level sound card, set the line input level
to maximum and use whatever is feeding it - a preamp or mixer - to set the
recording level so it gets near zero but never over.

--Ethan


Ethan,

Thank you very much.

I'm just curious. Why? What happens when you set the line level input on a
a consumer sound card to the maximum?

Is the maximum setting optimal in any way in terms of noise floor -- all
other things being ideal? Just curious as to why the maximum and not the
minimum, for example.

Thanks in advance,

Ed

"Ethan Winer" ethanw at ethanwiner dot com wrote:

Ed,

You already got great answers from the experts, and I'll just add this
simple recipe:

When recording using a consumer level sound card, set the line input level
to maximum and use whatever is feeding it - a preamp or mixer - to set the
recording level so it gets near zero but never over.

--Ethan


Ethan,

Thank you very much.

I'm just curious. Why? What happens when you set the line level input on a
a consumer sound card to the maximum?

Is the maximum setting optimal in any way in terms of noise floor -- all
other things being ideal? Just curious as to why the maximum and not the
minimum, for example.

Thanks in advance,

Ed

(Scott Dorsey) wrote in message ...
Ed Abbott wrote:

What precisely is recording volume on the "line in" of
a sound card?

There is a specification on the card somewhere, saying what voltage input
gives you 0 dBFS. It's different from unit to unit since there is no
real consumer level standard.

Is it true that the "line in" of a sound card does not
have a preamp?

Right. It takes a line input and not a mike input.



Let me say that Scott Dorsey is god of audio knowledge and I am but an
ignorant student but It sounded to me as if he wants to know what the
difference is between a line input and a mic input in terms of what
they do. So here is my ignorant perception, which may be a wrong, or
great way to understand it for the unwashed.

I always think of a line input with trim pot as a variable
resistor/impedence input. A lot like a faucet. Opening it up a
little is still holding back the full flow of the water. At a certain
point you have the water flowing smoothley which is optimum, and at
another point, wide open, it is rushing through wildly, which would be
analagous to distortion.

When you go into a microphone/preamp input, it tries to increase the
signal at almost any stage. So any input level would be signal plus so
much gain. That is sort of my working formula. Correct to taste))

Mike http://www.mmeproductions.com

(Scott Dorsey) wrote in message ...
Ed Abbott wrote:

What precisely is recording volume on the "line in" of
a sound card?

There is a specification on the card somewhere, saying what voltage input
gives you 0 dBFS. It's different from unit to unit since there is no
real consumer level standard.

Is it true that the "line in" of a sound card does not
have a preamp?

Right. It takes a line input and not a mike input.



Let me say that Scott Dorsey is god of audio knowledge and I am but an
ignorant student but It sounded to me as if he wants to know what the
difference is between a line input and a mic input in terms of what
they do. So here is my ignorant perception, which may be a wrong, or
great way to understand it for the unwashed.

I always think of a line input with trim pot as a variable
resistor/impedence input. A lot like a faucet. Opening it up a
little is still holding back the full flow of the water. At a certain
point you have the water flowing smoothley which is optimum, and at
another point, wide open, it is rushing through wildly, which would be
analagous to distortion.

When you go into a microphone/preamp input, it tries to increase the
signal at almost any stage. So any input level would be signal plus so
much gain. That is sort of my working formula. Correct to taste))

Mike http://www.mmeproductions.com

In article writes:

What precisely is recording volume on the "line in" of
a sound card?

Is it true that the "line in" of a sound card does not
have a preamp?

A preamp is the term for an input stage that has enough gain to use
with a microphone, which is upwards of 1000 times more gain than a
"line level" source such as a CD player or keyboard requires. So yes,
in a sense, the "mic in" of a sound card has a preamp and the "line
in" does not. In reality, one has the right amount of gain for a
microphone, the other has the right amount of gain for a line level
source.

This is confusing to me. Why have a recording volume
on the sound card at all if the sound coming into the
card is already line level?

"Line level" covers a pretty wide range (as does mic level). You need
to be able to adjust things somewhere so that a too-high signal level
doesn't overload the sound card input or analog-to-digital converter,
and you may need to boost a lower line level signal so that you get a
reasonable recording level. Both the position of the volume adjustment
slider and the meter will guide as to the right working range.

Here's why I ca I want to know how to set sound levels
on my mixer and on my sound card when recording my voice.
Am I better off cranking up the volume on my mixer or am I
better off cranking up the volume on my sound card when
making recordings of my voice?

If you're using a mixer after the microphone, then you're using the
mixer's mic preamp which is almost certainly better sounding than the
sound card's built-in mic preamp. You should set the mixer gain so
that you get a normal indication on the mixer's meters, then set the
line input gain for your sound card so that you get a normal
indication on the sound card or DAW's record level meter.

I'm thinking that maybe I should learn how to set sound levels
on my present card before purchasing a new card.

Yes, you should. This is fundamental to any recording chain and other
than the appearance of the controls and meters, will apply to any
system.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

What precisely is recording volume on the "line in" of
a sound card?

Is it true that the "line in" of a sound card does not
have a preamp?

A preamp is the term for an input stage that has enough gain to use
with a microphone, which is upwards of 1000 times more gain than a
"line level" source such as a CD player or keyboard requires. So yes,
in a sense, the "mic in" of a sound card has a preamp and the "line
in" does not. In reality, one has the right amount of gain for a
microphone, the other has the right amount of gain for a line level
source.

This is confusing to me. Why have a recording volume
on the sound card at all if the sound coming into the
card is already line level?

"Line level" covers a pretty wide range (as does mic level). You need
to be able to adjust things somewhere so that a too-high signal level
doesn't overload the sound card input or analog-to-digital converter,
and you may need to boost a lower line level signal so that you get a
reasonable recording level. Both the position of the volume adjustment
slider and the meter will guide as to the right working range.

Here's why I ca I want to know how to set sound levels
on my mixer and on my sound card when recording my voice.
Am I better off cranking up the volume on my mixer or am I
better off cranking up the volume on my sound card when
making recordings of my voice?

If you're using a mixer after the microphone, then you're using the
mixer's mic preamp which is almost certainly better sounding than the
sound card's built-in mic preamp. You should set the mixer gain so
that you get a normal indication on the mixer's meters, then set the
line input gain for your sound card so that you get a normal
indication on the sound card or DAW's record level meter.

I'm thinking that maybe I should learn how to set sound levels
on my present card before purchasing a new card.

Yes, you should. This is fundamental to any recording chain and other
than the appearance of the controls and meters, will apply to any
system.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

(Ed Abbott) wrote in message . com...

This is confusing to me. Why have a recording volume
on the sound card at all if the sound coming into the
card is already line level?

Here's the essence of my confusion: Does the sound
actually get amplified by the recording volume on
the sound card in the same way that a pre-amp amplifies
sound? If so, can the sound be distorted by the recording
volume on the line in?

The "line in" recording volume might make sense to me
if I thought of it as being pure math. I can imagine
the ADC (Analog to Digital Converter) taking the sound
pressure level and converting it to a number. I can
further imagine that number being bumped upwards or downwards
by a mathematical formula.


Hi,

I don't know for sure the answer to your question. But I have
wondered about the very same thing and believe that it is math. In
other words, when you change the settings on the mixer on the PC
screen, you perform either a multiplication or division on the digital
word at the output of the ADC. And the level is the level at the
output of the mult/div relative to the number of bits available.

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

In any event, the question is what is the 0 dB input setting of the
software mixer? Is it with the slider in the middle or some other
position? In other words, how can you set the mulitplying factor to
1? Then, keeping that fixed, adjust the output level of your mic mixer
going into the LINE IN while monitoring the software VU meters for the
largest signal without clipping.


Joe

(Ed Abbott) wrote in message . com...

This is confusing to me. Why have a recording volume
on the sound card at all if the sound coming into the
card is already line level?

Here's the essence of my confusion: Does the sound
actually get amplified by the recording volume on
the sound card in the same way that a pre-amp amplifies
sound? If so, can the sound be distorted by the recording
volume on the line in?

The "line in" recording volume might make sense to me
if I thought of it as being pure math. I can imagine
the ADC (Analog to Digital Converter) taking the sound
pressure level and converting it to a number. I can
further imagine that number being bumped upwards or downwards
by a mathematical formula.


Hi,

I don't know for sure the answer to your question. But I have
wondered about the very same thing and believe that it is math. In
other words, when you change the settings on the mixer on the PC
screen, you perform either a multiplication or division on the digital
word at the output of the ADC. And the level is the level at the
output of the mult/div relative to the number of bits available.

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

In any event, the question is what is the 0 dB input setting of the
software mixer? Is it with the slider in the middle or some other
position? In other words, how can you set the mulitplying factor to
1? Then, keeping that fixed, adjust the output level of your mic mixer
going into the LINE IN while monitoring the software VU meters for the
largest signal without clipping.


Joe

"Ed Abbott" wrote ...

"Ethan Winer" ethanw at ethanwiner dot com wrote:
You already got great answers from the experts, and I'll
just add this simple recipe:

When recording using a consumer level sound card, set
the line input level to maximum and use whatever is feeding
it - a preamp or mixer - to set the recording level so it gets
near zero but never over.

I'm just curious. Why? What happens when you set the line
level input on a consumer sound card to the maximum?

Wrong question. You should be asking: "What happens when
the audio level reaches zero (full-scale)? What happens is
moderate to horrible distortion that usually cannot be repaired

The input level control is just the method of adjusting the signal
level so that it is optimal (not to low "down in the mud", nor too
high "clipped") The correct setting is whatever it takes to keep
the audio level in the optimal range for the piece of equipment.
This is the case with all equipment, consumer or professional.

Is the maximum setting optimal in any way in terms of noise
floor -- all other things being ideal? Just curious as to why
the maximum and not the minimum, for example.

Exactly. At every point in the audio path, there is an optimal level.
If you are running too low, your signal-to-noise ratio will go down
to the point where system noise is interfering with your signal.
At the other end of the scale, if you are running too high, you risk
distortion from cliping and its artifacts.

"Ed Abbott" wrote ...

"Ethan Winer" ethanw at ethanwiner dot com wrote:
You already got great answers from the experts, and I'll
just add this simple recipe:

When recording using a consumer level sound card, set
the line input level to maximum and use whatever is feeding
it - a preamp or mixer - to set the recording level so it gets
near zero but never over.

I'm just curious. Why? What happens when you set the line
level input on a consumer sound card to the maximum?

Wrong question. You should be asking: "What happens when
the audio level reaches zero (full-scale)? What happens is
moderate to horrible distortion that usually cannot be repaired

The input level control is just the method of adjusting the signal
level so that it is optimal (not to low "down in the mud", nor too
high "clipped") The correct setting is whatever it takes to keep
the audio level in the optimal range for the piece of equipment.
This is the case with all equipment, consumer or professional.

Is the maximum setting optimal in any way in terms of noise
floor -- all other things being ideal? Just curious as to why
the maximum and not the minimum, for example.

Exactly. At every point in the audio path, there is an optimal level.
If you are running too low, your signal-to-noise ratio will go down
to the point where system noise is interfering with your signal.
At the other end of the scale, if you are running too high, you risk
distortion from cliping and its artifacts.

In any event, the question is what is the 0 dB input setting of the
software mixer? Is it with the slider in the middle or some other
position? In other words, how can you set the mulitplying factor to
1? Then, keeping that fixed, adjust the output level of your mic mixer
going into the LINE IN while monitoring the software VU meters for the
largest signal without clipping.


Joe

Thank you Joe for answering my question with
such incredible precision.

My software mixer is Goldwave.

Ok. Now I'm starting to understand. At least, I hope I am.

If I infer correctly from your post, I would assume the following:

-- Goldwave probably has a multiplier built into the "line in"
on the software mixer. That's why the noise floor rises on the
left level meter when I slide the "line in" to a higher volume.

The left channel on my sound card is defective and Goldwave is
multiplying it. This multiplication happens even with no sound
source present and no cables plugged into the card precisely because
of this multiplication.

This multiplication shows up as a rise in the bottom-most level of the
left channel.

-- In addition to setting levels in Goldwave, I can also go to the
sound card itself and set levels. In this case, it is an actual
analog amplifier that is kicking in that brings the line level up.

I infer this from Mike Rivers post above on this same thread.

I also infer this because setting a "line in" level of zero (the range
in Goldwave is zero to one hundred) gives me perfectly usable
sound that does not require me to raise the gain on my hardware
mixer (Behringer UB502) to the level where it would clip (in other
words, I only go into the yellow once in a while on the Behringer).

Therefore, setting the Goldwave software mixer to zero on "line in" must be
equivalent to multiplying by one (as you describe above). Otherwise, how
is it possible for me to get perfectly usable sound (just below 0db on my
Goldwave software mixer) with Goldwave "line in" set to zero?

I suppose the way for me to test this is to see if Goldwave "line in" sound
levels are always "in addition to" my soundcard sound levels. If I test
this and it doesn't work this way, than my theory falls apart.

In any case, much obliged to you for a deeper understanding of what was so
recently deeply mysterious to me.

I'm still figuring things out and am ever so grateful to those who set me
straight.

It's so much easier to get good results with right understanding.

Ed

In any event, the question is what is the 0 dB input setting of the
software mixer? Is it with the slider in the middle or some other
position? In other words, how can you set the mulitplying factor to
1? Then, keeping that fixed, adjust the output level of your mic mixer
going into the LINE IN while monitoring the software VU meters for the
largest signal without clipping.


Joe

Thank you Joe for answering my question with
such incredible precision.

My software mixer is Goldwave.

Ok. Now I'm starting to understand. At least, I hope I am.

If I infer correctly from your post, I would assume the following:

-- Goldwave probably has a multiplier built into the "line in"
on the software mixer. That's why the noise floor rises on the
left level meter when I slide the "line in" to a higher volume.

The left channel on my sound card is defective and Goldwave is
multiplying it. This multiplication happens even with no sound
source present and no cables plugged into the card precisely because
of this multiplication.

This multiplication shows up as a rise in the bottom-most level of the
left channel.

-- In addition to setting levels in Goldwave, I can also go to the
sound card itself and set levels. In this case, it is an actual
analog amplifier that is kicking in that brings the line level up.

I infer this from Mike Rivers post above on this same thread.

I also infer this because setting a "line in" level of zero (the range
in Goldwave is zero to one hundred) gives me perfectly usable
sound that does not require me to raise the gain on my hardware
mixer (Behringer UB502) to the level where it would clip (in other
words, I only go into the yellow once in a while on the Behringer).

Therefore, setting the Goldwave software mixer to zero on "line in" must be
equivalent to multiplying by one (as you describe above). Otherwise, how
is it possible for me to get perfectly usable sound (just below 0db on my
Goldwave software mixer) with Goldwave "line in" set to zero?

I suppose the way for me to test this is to see if Goldwave "line in" sound
levels are always "in addition to" my soundcard sound levels. If I test
this and it doesn't work this way, than my theory falls apart.

In any case, much obliged to you for a deeper understanding of what was so
recently deeply mysterious to me.

I'm still figuring things out and am ever so grateful to those who set me
straight.

It's so much easier to get good results with right understanding.

Ed

A preamp is the term for an input stage that has enough gain to use
with a microphone, which is upwards of 1000 times more gain than a
"line level" source such as a CD player or keyboard requires. So yes,
in a sense, the "mic in" of a sound card has a preamp and the "line
in" does not. In reality, one has the right amount of gain for a
microphone, the other has the right amount of gain for a line level
source.

Thanks so much! Wow! A high precision answer. It makes so much
more sense to think of the "line in" on a sound card as having an
analog amplifier that amplifies to some degree.

To then think of the mic pre-amp as an amplifier that amplifies orders
of magnitude more also makes sense. This is what I infer from your
post.

"Line level" covers a pretty wide range (as does mic level). You need
to be able to adjust things somewhere so that a too-high signal level
doesn't overload the sound card input or analog-to-digital converter,
and you may need to boost a lower line level signal so that you get a
reasonable recording level. Both the position of the volume adjustment
slider and the meter will guide as to the right working range.


Ok. Now I see that I am too formula-based in my thinking. Sounds like
setting levels is as much art as it is science.


Ed

A preamp is the term for an input stage that has enough gain to use
with a microphone, which is upwards of 1000 times more gain than a
"line level" source such as a CD player or keyboard requires. So yes,
in a sense, the "mic in" of a sound card has a preamp and the "line
in" does not. In reality, one has the right amount of gain for a
microphone, the other has the right amount of gain for a line level
source.

Thanks so much! Wow! A high precision answer. It makes so much
more sense to think of the "line in" on a sound card as having an
analog amplifier that amplifies to some degree.

To then think of the mic pre-amp as an amplifier that amplifies orders
of magnitude more also makes sense. This is what I infer from your
post.

"Line level" covers a pretty wide range (as does mic level). You need
to be able to adjust things somewhere so that a too-high signal level
doesn't overload the sound card input or analog-to-digital converter,
and you may need to boost a lower line level signal so that you get a
reasonable recording level. Both the position of the volume adjustment
slider and the meter will guide as to the right working range.


Ok. Now I see that I am too formula-based in my thinking. Sounds like
setting levels is as much art as it is science.


Ed

I'm replying to my own post because further
experimentation has proven me wrong.

I assumed that the "line in" volume control
on my Goldwave editor and the volume control
on my sound card are 2 separate entities.
They are not separate.

It turns out that the Goldwave "line in" volume
control is actually a software overide. I can
mute the "line in" on my sound card or I can turn
the volume way down on the sound card and Goldwave
ignores my actions.

This gives me more respect for Goldwave as I now
understand that it is controlling my soundcard in
a very direct way.

Ed Abbott

I'm replying to my own post because further
experimentation has proven me wrong.

I assumed that the "line in" volume control
on my Goldwave editor and the volume control
on my sound card are 2 separate entities.
They are not separate.

It turns out that the Goldwave "line in" volume
control is actually a software overide. I can
mute the "line in" on my sound card or I can turn
the volume way down on the sound card and Goldwave
ignores my actions.

This gives me more respect for Goldwave as I now
understand that it is controlling my soundcard in
a very direct way.

Ed Abbott

Ed,

What happens when you set the line level input on a a consumer sound card
to the maximum?

In consumer grade sound cards the volume control section is after the
analog-to-digital convertor. So if you feed the Line Input with a level
that's too high and reduce the volume in the software mixer, it's too late
and the signal is already distorted.

With most gear it's usually not recommended to turn inputs or outputs all
the way up. A lot of mixers and outboard compressors etc. have extra gain
available, so "all the way up" gives 10 or even 20 dB of added boost. But in
this particular case it's best to set the input level at max and use the
volume control of whatever is feeding the sound card's input.

--Ethan

Ed,

What happens when you set the line level input on a a consumer sound card
to the maximum?

In consumer grade sound cards the volume control section is after the
analog-to-digital convertor. So if you feed the Line Input with a level
that's too high and reduce the volume in the software mixer, it's too late
and the signal is already distorted.

With most gear it's usually not recommended to turn inputs or outputs all
the way up. A lot of mixers and outboard compressors etc. have extra gain
available, so "all the way up" gives 10 or even 20 dB of added boost. But in
this particular case it's best to set the input level at max and use the
volume control of whatever is feeding the sound card's input.

--Ethan

"Ethan Winer" ethanw at ethanwiner dot com wrote in message

Ed,

What happens when you set the line level input on a a consumer sound
card to the maximum?

In consumer grade sound cards the volume control section is after the
analog-to-digital convertor.

Sometimes. There still seem to be soundcards out there with analog input
gain controls. Among the highest quality cards, no input level controls at
all seems to be the norm. That means that they can suffer from clipping at
the input just as easily. However, their nominal signal levels are often
higher. OTOH, many of them have -10 dB and even some even have pro-audio
type mic inputs (example: Delta 1010LT). So input clipping is not a remote
possibility, even with them.

In some cards with the volume control following the ADC, highest resolution
is obtained with the volume control maxed out and the input voltage set just
below clipping. In other cards with the identical same volume control
following the ADC feature, highest resolution is obtained with the volume
control minimized just above a setting that mutes the input, but still the
input voltage should be set just below clipping.

So if you feed the Line Input with a
level that's too high and reduce the volume in the software mixer,
it's too late and the signal is already distorted.

This can be true

With most gear it's usually not recommended to turn inputs or outputs
all the way up. A lot of mixers and outboard compressors etc. have
extra gain available, so "all the way up" gives 10 or even 20 dB of
added boost. But in this particular case it's best to set the input
level at max and use the volume control of whatever is feeding the
sound card's input.

I find that it takes some fooling around to optimize gain settings. I hope
that exploring the two vastly different gain structures that are commonly
used, will help people find the right gain structure for their working
environment.

"Ethan Winer" ethanw at ethanwiner dot com wrote in message

Ed,

What happens when you set the line level input on a a consumer sound
card to the maximum?

In consumer grade sound cards the volume control section is after the
analog-to-digital convertor.

Sometimes. There still seem to be soundcards out there with analog input
gain controls. Among the highest quality cards, no input level controls at
all seems to be the norm. That means that they can suffer from clipping at
the input just as easily. However, their nominal signal levels are often
higher. OTOH, many of them have -10 dB and even some even have pro-audio
type mic inputs (example: Delta 1010LT). So input clipping is not a remote
possibility, even with them.

In some cards with the volume control following the ADC, highest resolution
is obtained with the volume control maxed out and the input voltage set just
below clipping. In other cards with the identical same volume control
following the ADC feature, highest resolution is obtained with the volume
control minimized just above a setting that mutes the input, but still the
input voltage should be set just below clipping.

So if you feed the Line Input with a
level that's too high and reduce the volume in the software mixer,
it's too late and the signal is already distorted.

This can be true

With most gear it's usually not recommended to turn inputs or outputs
all the way up. A lot of mixers and outboard compressors etc. have
extra gain available, so "all the way up" gives 10 or even 20 dB of
added boost. But in this particular case it's best to set the input
level at max and use the volume control of whatever is feeding the
sound card's input.

I find that it takes some fooling around to optimize gain settings. I hope
that exploring the two vastly different gain structures that are commonly
used, will help people find the right gain structure for their working
environment.

In article writes:

I'm just curious. Why? What happens when you set the line
level input on a consumer sound card to the maximum?

Wrong question. You should be asking: "What happens when
the audio level reaches zero (full-scale)? What happens is
moderate to horrible distortion that usually cannot be repaired

Actually, that's a valid question. The way that the input volume
control on a sound card usually works adds noise and may reduce
resolution when it's turned down from wide open. This is why the card
works best when it's operating at line level with no input
attenuation. If you adjust the signal level going in by using a level
or gain control on whatever is feeding it, you'll be ahead of the
game, or at least you can avoid doing some damage.

Of course if there is no other place to adjust the record level, then
by all means do what's necessary. A couple of dB of noise or a couple
of bits fewer resolution is preferable to digital clipping.

This explanation applies to line inputs, which are usually operated at
unity gain or below (as you turn the level slider down). Microphone
inputs have gain, and noise increases as you increase the gain. But
with a microphone connected directly to a sound card's mic input, you
don't have any other place to adjust the record level, so you do what
you gotta do.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

I'm just curious. Why? What happens when you set the line
level input on a consumer sound card to the maximum?

Wrong question. You should be asking: "What happens when
the audio level reaches zero (full-scale)? What happens is
moderate to horrible distortion that usually cannot be repaired

Actually, that's a valid question. The way that the input volume
control on a sound card usually works adds noise and may reduce
resolution when it's turned down from wide open. This is why the card
works best when it's operating at line level with no input
attenuation. If you adjust the signal level going in by using a level
or gain control on whatever is feeding it, you'll be ahead of the
game, or at least you can avoid doing some damage.

Of course if there is no other place to adjust the record level, then
by all means do what's necessary. A couple of dB of noise or a couple
of bits fewer resolution is preferable to digital clipping.

This explanation applies to line inputs, which are usually operated at
unity gain or below (as you turn the level slider down). Microphone
inputs have gain, and noise increases as you increase the gain. But
with a microphone connected directly to a sound card's mic input, you
don't have any other place to adjust the record level, so you do what
you gotta do.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

Ok. Now I see that I am too formula-based in my thinking. Sounds like
setting levels is as much art as it is science.

Actually, it's just part of the craft of recording. You need to find a
good setting that gives the sensitivity to get over the system noise
and not such high sensitivity that you get digital overloads on peaks.
When you find that level - for the recording you're about to do, not
for as long as you own the sound card - you leave it alone.

Sometimes we "ride the gain" when working with live sound sources, but
this is to even out the performance in a human manner rather than try
to keep it at a high level at all times. You can't really ride gain
with the digital adjustments that sound cards give you. There's
usually too much delay between when you move the on-screen slider and
when that adjustment actually takes effect. An analog control (like
the slider on a mixer or knob on a mic preamp) works instantly, so you
can anticipate when the singer is about to bellow (body language
helps) and get ready to pull the level back for a word or two, then
bring it back to the nominal setting.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

Ok. Now I see that I am too formula-based in my thinking. Sounds like
setting levels is as much art as it is science.

Actually, it's just part of the craft of recording. You need to find a
good setting that gives the sensitivity to get over the system noise
and not such high sensitivity that you get digital overloads on peaks.
When you find that level - for the recording you're about to do, not
for as long as you own the sound card - you leave it alone.

Sometimes we "ride the gain" when working with live sound sources, but
this is to even out the performance in a human manner rather than try
to keep it at a high level at all times. You can't really ride gain
with the digital adjustments that sound cards give you. There's
usually too much delay between when you move the on-screen slider and
when that adjustment actually takes effect. An analog control (like
the slider on a mixer or knob on a mic preamp) works instantly, so you
can anticipate when the singer is about to bellow (body language
helps) and get ready to pull the level back for a word or two, then
bring it back to the nominal setting.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Ed Abbott wrote in message ...
In any event, the question is what is the 0 dB input setting of the
software mixer? Is it with the slider in the middle or some other
position? In other words, how can you set the mulitplying factor to
1? Then, keeping that fixed, adjust the output level of your mic mixer
going into the LINE IN while monitoring the software VU meters for the
largest signal without clipping.


Joe

Therefore, setting the Goldwave software mixer to zero on "line in" must be
equivalent to multiplying by one (as you describe above). Otherwise, how
is it possible for me to get perfectly usable sound (just below 0db on my
Goldwave software mixer) with Goldwave "line in" set to zero?

I suppose the way for me to test this is to see if Goldwave "line in" sound
levels are always "in addition to" my soundcard sound levels. If I test
this and it doesn't work this way, than my theory falls apart.


Hi Ed,

Keep in mind that my answer is not an expert's opinion. It is merely
the model that I have in my mind about how this might work. Not
knowing the details of how a PC interfaces to a sound card, I may very
well be wrong!

Regardless, it's always best to have first hand knowledge obtained by
actual testing. To be sure you might want to try the following:

1) Set your Goldwave software mixer to what you think is the zeros dB
position, and leave your Behringer mixer output to the level that has
given you good results. Whistle a constant tone into mic as a test
signal, and make a 2 second recording. You should then see a
sinusoidal signal on your display.

2) Next, crank up the output of your Behringer mixer enough so that
you severely clip the signal while leaving the Goldwave settings
unchanged. Now make another 2 second recording of the same whistle.
You should now see a sinuoisal signal with its tops and bottoms
flattened out.

3) Lastly, lower the mixer setting on your Goldwave software until the
signal is no longer being clipped while leaving the Behringer settings
unchanged. Record the same whistle once again. If our understanding of
this is correct, you should still see a sinusoidal signal with its
top and bottom flattened out only smaller in vertical size. This would
imply that the software is doing only a mathematical operation and not
controlling the analog electronics of your sound card.

Joe

Ed Abbott wrote in message ...
In any event, the question is what is the 0 dB input setting of the
software mixer? Is it with the slider in the middle or some other
position? In other words, how can you set the mulitplying factor to
1? Then, keeping that fixed, adjust the output level of your mic mixer
going into the LINE IN while monitoring the software VU meters for the
largest signal without clipping.


Joe

Therefore, setting the Goldwave software mixer to zero on "line in" must be
equivalent to multiplying by one (as you describe above). Otherwise, how
is it possible for me to get perfectly usable sound (just below 0db on my
Goldwave software mixer) with Goldwave "line in" set to zero?

I suppose the way for me to test this is to see if Goldwave "line in" sound
levels are always "in addition to" my soundcard sound levels. If I test
this and it doesn't work this way, than my theory falls apart.


Hi Ed,

Keep in mind that my answer is not an expert's opinion. It is merely
the model that I have in my mind about how this might work. Not
knowing the details of how a PC interfaces to a sound card, I may very
well be wrong!

Regardless, it's always best to have first hand knowledge obtained by
actual testing. To be sure you might want to try the following:

1) Set your Goldwave software mixer to what you think is the zeros dB
position, and leave your Behringer mixer output to the level that has
given you good results. Whistle a constant tone into mic as a test
signal, and make a 2 second recording. You should then see a
sinusoidal signal on your display.

2) Next, crank up the output of your Behringer mixer enough so that
you severely clip the signal while leaving the Goldwave settings
unchanged. Now make another 2 second recording of the same whistle.
You should now see a sinuoisal signal with its tops and bottoms
flattened out.

3) Lastly, lower the mixer setting on your Goldwave software until the
signal is no longer being clipped while leaving the Behringer settings
unchanged. Record the same whistle once again. If our understanding of
this is correct, you should still see a sinusoidal signal with its
top and bottom flattened out only smaller in vertical size. This would
imply that the software is doing only a mathematical operation and not
controlling the analog electronics of your sound card.

Joe

"Joseph Raymond" wrote in message

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

Actually, it is the case for most audio chipsets. Take a look block diagram
in the datasheet below. Between the input selector and the A/D there is a
small block called PGA (Programable Gain Amplifier) that can be set from 0
to 22.5 dB gain in 1.5 dB steps. And this is for a part that costs $3...!

http://www.analog.com/UploadedFiles/...7AD1881A_0.pdf

/Preben Friis

"Joseph Raymond" wrote in message

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

Actually, it is the case for most audio chipsets. Take a look block diagram
in the datasheet below. Between the input selector and the A/D there is a
small block called PGA (Programable Gain Amplifier) that can be set from 0
to 22.5 dB gain in 1.5 dB steps. And this is for a part that costs $3...!

http://www.analog.com/UploadedFiles/...7AD1881A_0.pdf

/Preben Friis

"Preben Friis" wrote in message

"Joseph Raymond" wrote in message

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

Actually, it is the case for most audio chipsets. Take a look block
diagram in the datasheet below. Between the input selector and the
A/D there is a small block called PGA (Programable Gain Amplifier)
that can be set from 0 to 22.5 dB gain in 1.5 dB steps. And this is
for a part that costs $3...!
http://www.analog.com/UploadedFiles/...7AD1881A_0.pdf

Unfortunately, I've got quite a bit of experience with this device. Not
exactly the device of choice for high quality audio production:

Test results for a typical device from the SoundMax series:

Frequency response (40 Hz - 15 kHz), +9.68, -12.97 dB
Noise level, -84.6 dB (A)
Dnamic range, 82.0 dB (A)
HD, 0.0044 %
Intermodulation distortion, 11.441 %

"Preben Friis" wrote in message

"Joseph Raymond" wrote in message

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

Actually, it is the case for most audio chipsets. Take a look block
diagram in the datasheet below. Between the input selector and the
A/D there is a small block called PGA (Programable Gain Amplifier)
that can be set from 0 to 22.5 dB gain in 1.5 dB steps. And this is
for a part that costs $3...!
http://www.analog.com/UploadedFiles/...7AD1881A_0.pdf

Unfortunately, I've got quite a bit of experience with this device. Not
exactly the device of choice for high quality audio production:

Test results for a typical device from the SoundMax series:

Frequency response (40 Hz - 15 kHz), +9.68, -12.97 dB
Noise level, -84.6 dB (A)
Dnamic range, 82.0 dB (A)
HD, 0.0044 %
Intermodulation distortion, 11.441 %

On 1 Dec 2004 14:42:55 -0800, (Joseph
Raymond) wrote:
I don't know for sure the answer to your question. But I have
wondered about the very same thing and believe that it is math. In
other words, when you change the settings on the mixer on the PC
screen, you perform either a multiplication or division on the digital
word at the output of the ADC. And the level is the level at the
output of the mult/div relative to the number of bits available.

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

In any event, the question is what is the 0 dB input setting of the
software mixer? Is it with the slider in the middle or some other
position? In other words, how can you set the mulitplying factor to
1? Then, keeping that fixed, adjust the output level of your mic mixer
going into the LINE IN while monitoring the software VU meters for the
largest signal without clipping.

To add complexity to these questions, the level control you see in
your recording app is not always a second view of your Windows Volume
Control. When I start Audiotools, its sliders are at 0dB, regardless
of where my input Windows Volume Control sliders are set.

I find that cutting the gain at the Windows Volume Control provides
much better results than an equivalent reduction within Audiotools.
Even though the analog input to my sound interface is constant, if I
crank the Windows Volume Control up and make a comparable gain
reduction within Audiotools, the waveform appears compressed. Crank
the Windows Volume Control even higher and the recorded waveform is
clipped, even though the values in the digital file are nowhere near
maximum. Same behavior is observed recording with Audacity.

I've been assuming this is all happening in the digital domain, where
one would hope math is math, but it clearly it is not! Either the
Windows Volume Control must operate in the analog world before the
ADC, or it must be able to multiply as well as divide, and it must be
able to multiply so much that it can clip in the digital domain.

Another way of saying that would be to say that the (possibly digital
counterpart of the) "0dB" setting of the Windows Volume Control must
be well below its maximum setting. (At least with some audio
hardware...)

To add one more variable, I've found that Alex Mina's AC97 Mixer app,
which talks directly to AC97 audio hardware, can reach gain settings
the Windows Volume Control does not offer. At least with some
hardware...

According to its datasheet, the AKM AK4584 chip in my Transit USB has
a +18dB Input Programmable Gain Amp (0.5dB steps) ahead of the ADC.
With this IPGA set at 0 dB, it is supposed to take 3.0 Vpp of audio to
produce digital full scale. Cranking the gain up to +18 raises the
noise floor 10dB, so it sounds like this really is an analog
amplifier. And I can clearly get clipping with way less than 3.0 Vpp,
so the Transit drivers must have this IPGA set above 0 dB.

Then there are the 0/14/20/26 dB steps that M-Audio offers as "Mic
Boost" in their control panel. I don't see how that is implemented, or
how it relates to the +18 dB IPGA in the audio chip. And I haven't a
clue how the input Windows Volume Control is hooked up to all of this.

So is there a way to tell whether the Windows Volume Control for a
particular interface is operating before or after the ADC? I have a
feeling it is different for different audio devices, and possibly for
different driver versions...

Loren

On 1 Dec 2004 14:42:55 -0800, (Joseph
Raymond) wrote:
I don't know for sure the answer to your question. But I have
wondered about the very same thing and believe that it is math. In
other words, when you change the settings on the mixer on the PC
screen, you perform either a multiplication or division on the digital
word at the output of the ADC. And the level is the level at the
output of the mult/div relative to the number of bits available.

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

In any event, the question is what is the 0 dB input setting of the
software mixer? Is it with the slider in the middle or some other
position? In other words, how can you set the mulitplying factor to
1? Then, keeping that fixed, adjust the output level of your mic mixer
going into the LINE IN while monitoring the software VU meters for the
largest signal without clipping.

To add complexity to these questions, the level control you see in
your recording app is not always a second view of your Windows Volume
Control. When I start Audiotools, its sliders are at 0dB, regardless
of where my input Windows Volume Control sliders are set.

I find that cutting the gain at the Windows Volume Control provides
much better results than an equivalent reduction within Audiotools.
Even though the analog input to my sound interface is constant, if I
crank the Windows Volume Control up and make a comparable gain
reduction within Audiotools, the waveform appears compressed. Crank
the Windows Volume Control even higher and the recorded waveform is
clipped, even though the values in the digital file are nowhere near
maximum. Same behavior is observed recording with Audacity.

I've been assuming this is all happening in the digital domain, where
one would hope math is math, but it clearly it is not! Either the
Windows Volume Control must operate in the analog world before the
ADC, or it must be able to multiply as well as divide, and it must be
able to multiply so much that it can clip in the digital domain.

Another way of saying that would be to say that the (possibly digital
counterpart of the) "0dB" setting of the Windows Volume Control must
be well below its maximum setting. (At least with some audio
hardware...)

To add one more variable, I've found that Alex Mina's AC97 Mixer app,
which talks directly to AC97 audio hardware, can reach gain settings
the Windows Volume Control does not offer. At least with some
hardware...

According to its datasheet, the AKM AK4584 chip in my Transit USB has
a +18dB Input Programmable Gain Amp (0.5dB steps) ahead of the ADC.
With this IPGA set at 0 dB, it is supposed to take 3.0 Vpp of audio to
produce digital full scale. Cranking the gain up to +18 raises the
noise floor 10dB, so it sounds like this really is an analog
amplifier. And I can clearly get clipping with way less than 3.0 Vpp,
so the Transit drivers must have this IPGA set above 0 dB.

Then there are the 0/14/20/26 dB steps that M-Audio offers as "Mic
Boost" in their control panel. I don't see how that is implemented, or
how it relates to the +18 dB IPGA in the audio chip. And I haven't a
clue how the input Windows Volume Control is hooked up to all of this.

So is there a way to tell whether the Windows Volume Control for a
particular interface is operating before or after the ADC? I have a
feeling it is different for different audio devices, and possibly for
different driver versions...

Loren

"Preben Friis" wrote in message ...
"Joseph Raymond" wrote in message

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

Actually, it is the case for most audio chipsets. Take a look block diagram
in the datasheet below. Between the input selector and the A/D there is a
small block called PGA (Programable Gain Amplifier) that can be set from 0
to 22.5 dB gain in 1.5 dB steps. And this is for a part that costs $3...!

http://www.analog.com/UploadedFiles/...7AD1881A_0.pdf

/Preben Friis


OK, and thanks. I did look at that document and saw the PGA which is
downstream of both the MIC IN and LINE IN. So, to answer Ed Abbott's
question, is sending a control word to the PGA the way the gain is
typically controlled on PCs?

Joe

"Preben Friis" wrote in message ...
"Joseph Raymond" wrote in message

If the level control actually controlled the gain of the analog
preamp, then some control words would have to be sent to the sound
card's ADC to either change the reference voltage or to change the
sound card's preamp gain. Based on economic considerations, I doubt
that that is the case.

Actually, it is the case for most audio chipsets. Take a look block diagram
in the datasheet below. Between the input selector and the A/D there is a
small block called PGA (Programable Gain Amplifier) that can be set from 0
to 22.5 dB gain in 1.5 dB steps. And this is for a part that costs $3...!

http://www.analog.com/UploadedFiles/...7AD1881A_0.pdf

/Preben Friis


OK, and thanks. I did look at that document and saw the PGA which is
downstream of both the MIC IN and LINE IN. So, to answer Ed Abbott's
question, is sending a control word to the PGA the way the gain is
typically controlled on PCs?

Joe