Audio volume level passed to apps lower than expected


Frank O'Donnell K6FOD
 

This week I've been using SDR Console v3.1 to pass audio output via Muzychenko's Virtual Audio Cable software to various apps. The PC is running Windows 10 Pro build 19043.

The levels I'm seeing, even when all controls are maximized, are a good bit lower than I'm remembering when working with comparable signals in this way a few months ago. The apps include audio editors such as Audacity and GoldWave, as well as WSJT-X.

So far I've checked:

-- In SDR Console, the output level slider (in the lefthand pane just below the output device selection and RX frequency) is maximized.

-- In Windows' Sound settings, Line 1 (Virtual Audio Cable) is selected as input, with volume set to maximum.

-- For those apps that have an input sound control, level is maximized.

Is there anything else worth checking? Virtual Audio Cable has a checkbox to enable volume control, but the control itself doesn't appear in the VAC control panel. I gather this would be the volume control within Windows' Sound menu?

Thanks for any possible ideas,


Dale Elshoff WB8CJW
 

Hi Frank,

Could the noise reduction be enabled?  Audio equalizer not set right?



Dale


On 9/14/2021 8:42 PM, Frank O'Donnell K6FOD wrote:
This week I've been using SDR Console v3.1 to pass audio output via Muzychenko's Virtual Audio Cable software to various apps. The PC is running Windows 10 Pro build 19043.

The levels I'm seeing, even when all controls are maximized, are a good bit lower than I'm remembering when working with comparable signals in this way a few months ago. The apps include audio editors such as Audacity and GoldWave, as well as WSJT-X.

So far I've checked:

-- In SDR Console, the output level slider (in the lefthand pane just below the output device selection and RX frequency) is maximized.

-- In Windows' Sound settings, Line 1 (Virtual Audio Cable) is selected as input, with volume set to maximum.

-- For those apps that have an input sound control, level is maximized.

Is there anything else worth checking? Virtual Audio Cable has a checkbox to enable volume control, but the control itself doesn't appear in the VAC control panel. I gather this would be the volume control within Windows' Sound menu?

Thanks for any possible ideas,


Frank O'Donnell K6FOD
 

Thanks, Dale, good ideas. In my case, noise reduction is not enabled.

As for the equalizer, it's set with each of the vertical sliders at mid-range so the graphic shows all of them at zero (neither + nor -). I see the equalizer's checkbox to enable it is not ticked. I assume this is all the default, as I've never played with it. Do you think the settings as shown in your screen print are more effective?


Simon Brown
 

Screenshots,

 

Always love to see a screenshot.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Frank O'Donnell K6FOD
Sent: 15 September 2021 05:58
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Audio volume level passed to apps lower than expected

 

Thanks, Dale, good ideas. In my case, noise reduction is not enabled.

As for the equalizer, it's set with each of the vertical sliders at mid-range so the graphic shows all of them at zero (neither + nor -). I see the equalizer's checkbox to enable it is not ticked. I assume this is all the default, as I've never played with it. Do you think the settings as shown in your screen print are more effective?


--
- + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Frank O'Donnell K6FOD
 

On Tue, Sep 14, 2021 at 11:16 PM, Simon Brown wrote:
Always love to see a screenshot.


Ryan Butler
 

AGC is off and your gain is too low?


On Wed, Sep 15, 2021 at 10:14 AM Frank O'Donnell K6FOD <gio@...> wrote:
On Tue, Sep 14, 2021 at 11:16 PM, Simon Brown wrote:
Always love to see a screenshot.


Frank O'Donnell K6FOD
 
Edited

On Wed, Sep 15, 2021 at 08:23 AM, Ryan Butler wrote:
AGC is off and your gain is too low?
The AGC is indeed off.

I wouldn't say the gain (signal levels as seen in waterfall) is too low. This appears normal. It's the level of the audio output I'm looking at.


Tony_AD0VC
 

Frank,

When you have AGC off, there are sliders in the AGC section that you use to adjust the gain. To the right of the AGC buttons  is an icon to click for the sliders and another for the graph. Adjust the slope and threshold sliders to get the level you want.

Tony


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Frank O'Donnell K6FOD <gio@...>
Sent: Wednesday, September 15, 2021 11:06 AM
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] Audio volume level passed to apps lower than expected
 

[Edited Message Follows]

On Wed, Sep 15, 2021 at 08:23 AM, Ryan Butler wrote:
AGC is off and your gain is too low?
The AGC is indeed off.

I wouldn't say the gain (signal levels as seen in waterfall) is too low. This appears normal. It's the level of the audio output I'm looking at.


Tony_AD0VC
 

Sorry, I meant the gain slider. Slope and threshold are only visible with AGC on. With it off you get a gain slider.

Tony


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Tony_AD0VC <canthony15@...>
Sent: Wednesday, September 15, 2021 11:19 AM
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] Audio volume level passed to apps lower than expected
 
Frank,

When you have AGC off, there are sliders in the AGC section that you use to adjust the gain. To the right of the AGC buttons  is an icon to click for the sliders and another for the graph. Adjust the slope and threshold sliders to get the level you want.

Tony


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Frank O'Donnell K6FOD <gio@...>
Sent: Wednesday, September 15, 2021 11:06 AM
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] Audio volume level passed to apps lower than expected
 

[Edited Message Follows]

On Wed, Sep 15, 2021 at 08:23 AM, Ryan Butler wrote:
AGC is off and your gain is too low?
The AGC is indeed off.

I wouldn't say the gain (signal levels as seen in waterfall) is too low. This appears normal. It's the level of the audio output I'm looking at.


Frank O'Donnell K6FOD
 

Thanks, Tony. I see that when I have AGC off, the gain slider in that section had been set to minimum. Moving that slider up and down doesn't affect the RF signal level as seen in the waterfall or dBm meter. However, it does significantly affect the audio output level, and by moving it up I get a strong input level in the apps receiving audio from SDR Console. So problem solved -- thanks again!

Just so I understand this, am I right in thinking that the AGC slider acts at the IF stage? Thus it doesn't affect RF levels reported, but will affect the audio output since that's downstream? Also -- it appears that it doesn't affect levels as recorded in I/Q .wav files, which I gather are taken before the IF stage?

Frank


Tony_AD0VC
 

Frank,

The waterfall and spectrum are upstream from the AGC function in the DSP panel. I'm not the one to ask for the particulars but I would guess that the AGC is part of the demodulator function. Some SDRs do have a hardware AGC function as well but that is not what is being controlled in the DSP panel of SDRC.

Tony


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Frank O'Donnell K6FOD <gio@...>
Sent: Wednesday, September 15, 2021 12:31 PM
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] Audio volume level passed to apps lower than expected
 
Thanks, Tony. I see that when I have AGC off, the gain slider in that section had been set to minimum. Moving that slider up and down doesn't affect the RF signal level as seen in the waterfall or dBm meter. However, it does significantly affect the audio output level, and by moving it up I get a strong input level in the apps receiving audio from SDR Console. So problem solved -- thanks again!

Just so I understand this, am I right in thinking that the AGC slider acts at the IF stage? Thus it doesn't affect RF levels reported, but will affect the audio output since that's downstream? Also -- it appears that it doesn't affect levels as recorded in I/Q .wav files, which I gather are taken before the IF stage?

Frank


jdow
 

AGC off? Have you changed the AGC Gain control?
{^_^}

On 20210915 08:14:28, Frank O'Donnell K6FOD wrote:
On Tue, Sep 14, 2021 at 11:16 PM, Simon Brown wrote:
Always love to see a screenshot.


jdow
 

Adjust the AG pane's Gain control. Listen to it. Ignore what the waterfall and other stuff do. Just listen. You seem to be expecting behavior that won't happen.

One thing to paste into your head is that SDRs are not simulating analog receiver processes. They use other techniques that have no (practical) equivalent in analog receivers. (Pardon me while I invest in a case of insane giggles imagining the amount of circuitry needed to take an analog fourier transform.... A 1 million band graphics equalizer anyone? Pardon me please. Sometimes my mind veers off into strange places. {O.O} REALLY strange places.) Simon's design seems to be further off analog prototypes than most at a guess.

{^_^}

On 20210915 11:31:08, Frank O'Donnell K6FOD wrote:
Thanks, Tony. I see that when I have AGC off, the gain slider in that section had been set to minimum. Moving that slider up and down doesn't affect the RF signal level as seen in the waterfall or dBm meter. However, it does significantly affect the audio output level, and by moving it up I get a strong input level in the apps receiving audio from SDR Console. So problem solved -- thanks again!

Just so I understand this, am I right in thinking that the AGC slider acts at the IF stage? Thus it doesn't affect RF levels reported, but will affect the audio output since that's downstream? Also -- it appears that it doesn't affect levels as recorded in I/Q .wav files, which I gather are taken before the IF stage?

Frank


jdow
 

The VERY common technique for AGC in SDRs turns the whole chain around backwards. It measures the input, calculates what is needed to get the desired output, and applies that to the signal leaving the AGC process. When everything is "float" type digits it does not matter if you run filters and other "IF" processing at levels of 0.0001 rms or 1.0 rms. And the gain can be anything within the range of "float" type digits for AGC. (I did find a bug in FM stereo demodulators that were running at a level of 1.0 getting a value in a digital feedback loop, the phase lock loop for the stereo demodulator, that dropped one of the terms down below the range of a 32 bit floating point (float) number. The loop did not work the way I "knew" it should work so I spent time tracking it down and figuring out a somewhat rude but very effective fix.)

{^_^}

On 20210915 14:46:31, Tony_AD0VC wrote:
Frank,

The waterfall and spectrum are upstream from the AGC function in the DSP panel. I'm not the one to ask for the particulars but I would guess that the AGC is part of the demodulator function. Some SDRs do have a hardware AGC function as well but that is not what is being controlled in the DSP panel of SDRC.

Tony


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Frank O'Donnell K6FOD <gio@...>
Sent: Wednesday, September 15, 2021 12:31 PM
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] Audio volume level passed to apps lower than expected
 
Thanks, Tony. I see that when I have AGC off, the gain slider in that section had been set to minimum. Moving that slider up and down doesn't affect the RF signal level as seen in the waterfall or dBm meter. However, it does significantly affect the audio output level, and by moving it up I get a strong input level in the apps receiving audio from SDR Console. So problem solved -- thanks again!

Just so I understand this, am I right in thinking that the AGC slider acts at the IF stage? Thus it doesn't affect RF levels reported, but will affect the audio output since that's downstream? Also -- it appears that it doesn't affect levels as recorded in I/Q .wav files, which I gather are taken before the IF stage?

Frank


Frank O'Donnell K6FOD
 

Thanks for the comments on this.

So I'm gathering this: When I output audio from SDR Console and pass it to an app through Virtual Audio Cable, there are four places I can adjust settings to increase/decrease the audio level seen at the input to the app:

-- In SDR Console, with AGC turned off, adjust the gain slider in the AGC area

-- In SDR Console, under Playback device, adjust the output audio level slider

-- In Windows sound settings, under Input, select the Virtual Audio Cable line that I'm using to pass the audio, click on Device properties, adjust the volume slider

-- If the app that the audio is being sent to has any input gain/volume controls, adjust those

If anyone can think of any other settings to play with to raise/lower the audio level seen at the input to the app receiving the audio, it would be a great help to know about them.


Siegfried Jackstien
 

In console also with agc on
There are sliders also for auto agc
Preset us 130 db... I had better results with turning it down a bit.. Say 60 or 65 db
And try what slope setting  you need

Dg9bfc sigj

Am 17.09.2021 01:01 schrieb Frank O'Donnell K6FOD <gio@...>:

Thanks for the comments on this.

So I'm gathering this: When I output audio from SDR Console and pass it to an app through Virtual Audio Cable, there are four places I can adjust settings to increase/decrease the audio level seen at the input to the app:

-- In SDR Console, with AGC turned off, adjust the gain slider in the AGC area

-- In SDR Console, under Playback device, adjust the output audio level slider

-- In Windows sound settings, under Input, select the Virtual Audio Cable line that I'm using to pass the audio, click on Device properties, adjust the volume slider

-- If the app that the audio is being sent to has any input gain/volume controls, adjust those

If anyone can think of any other settings to play with to raise/lower the audio level seen at the input to the app receiving the audio, it would be a great help to know about them.


jdow
 

Um, why the obsession with this?

Most front ends have a gain control on them. Some, such as rtlsdr dongles,  have local AGCs. Hopefully those are left off where practical to give you some means of calibrating the system. AirSpy HF+ models are an exception. And they don't calibrate well as a result.

Within an rtlsdr dongle there are three gain controls. Each of them affect the antenna to consumer level for SSB and AM related modes. As it happens ALL analog gain controls in the system also have an influence on both system noise figure and dynamic range as a tradeoff. Once past the A/D converter all gain controls are equivalent and do the same thing for SSB and AM paths. Adjust them to comfortable settings and move on.

{O.O}

On 20210916 16:01:25, Frank O'Donnell K6FOD wrote:
Thanks for the comments on this.

So I'm gathering this: When I output audio from SDR Console and pass it to an app through Virtual Audio Cable, there are four places I can adjust settings to increase/decrease the audio level seen at the input to the app:

-- In SDR Console, with AGC turned off, adjust the gain slider in the AGC area

-- In SDR Console, under Playback device, adjust the output audio level slider

-- In Windows sound settings, under Input, select the Virtual Audio Cable line that I'm using to pass the audio, click on Device properties, adjust the volume slider

-- If the app that the audio is being sent to has any input gain/volume controls, adjust those

If anyone can think of any other settings to play with to raise/lower the audio level seen at the input to the app receiving the audio, it would be a great help to know about them.