Find PC's Audio Out Voltage without CRO

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Is there any way to obtain a numerical readout of the maximum voltage
swing on the stereo headphone output of a PC without using a CRO or
meter?

I am thinking there must be some software that will do this.

This is to help those who do not have test gear.

Bob Griffin

Re: Find PC's Audio Out Voltage without CRO
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Pead the datashees for the parts involved and compute from there....

--  
  \_(?)_

Re: Find PC's Audio Out Voltage without CRO
On Sun, 24 Apr 2016 11:56:10 +1000, Bob Griffin

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What's a CRO?   Oh, a Cathode Ray Oscilloscope.  Got it.

There is plenty of sound card control software available for the PC
that includes an output indicator.  The problem is that the indication
is usually a guess based on the sound card amplifier gain.  So, you
get to calibrate the readings in order to get an accurate output.
There is also oscilloscope emulation software such as:
<http://www.sillanumsoft.org
but that only shows the level of the audio input, not the output.

Perhaps a PC VU meter.  Lots to choose from:
<https://www.google.com/#q=pc+vu+meter
all of which again give the audio input or mixer levels, not the
output level.

I'm out of ideas.  Since there's nothing on a sound card that connects
to the audio output jack, what can be used as an input to measure
something, methinks it can't be done unless you either use one channel
to measure the level on the other channel, or you add a 2nd sound card
or USB sound dongle.
<https://www.google.com/search?q=usb+sound+dongle&tbm=isch

The 2nd sound card is not that horrible a solution.  Let's say you're
using an internal PCI or motherboard sound card for driving the
headphone.  Add a USB sound dongle to the machine.  Install a 3.5mm
earphone jack "tee" connector into the internal sound card output
port.  Run a cable from one port of the "tee" to the input of the USB
sound dongle.  The other port goes to the earphone.  Install and run
any of the vu meter programs and have it monitor the USB sound dongle.
Now, you're monitoring the sound output instead of the input or mixer.
Of course, you'll need to calibrate this thing, but you only do that
once.  Umm... look into software that saves your sound card settings
as many programs like to change those settings.

I have the feeling that this isn't exactly what you want.  Perhaps it
would be helpful if you disclose more about what you're trying to
accomplish?



--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Find PC's Audio Out Voltage without CRO
wrote:

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It's for a rather delicate stereo front end, and to prevent
overdriving, without having to hook up external test gear in each
instance.

I think the closest I will get is playing the track through an audio
editing application, like Audacity, and calibrating the VU meters.

Obviously, such programs can read the output voltage. Would seem easy
enough to write a app that could provide a numeric readout.

Bob Griffin

Re: Find PC's Audio Out Voltage without CRO
On Sunday, 24 April 2016 08:47:06 UTC+1, Bob Griffin  wrote:

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Oscilloscope software + 2nd soundcard, as John said. Might not be very useful for the averag user though.

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make it less delicate? Use ears to detect overdrive?


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Reporting voltage is not one of a soundcard's functions afaik. If they read dc you could caibrate near enough with a new battery, but they're ac only.  


NT

Re: Find PC's Audio Out Voltage without CRO
On Sun, 24 Apr 2016 01:02:21 -0700 (PDT), snipped-for-privacy@gmail.com wrote:


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Yes, from the responses so far, this appears to be the case.

However, this pertaining to Visual Analyzer might be relevant.

http://www.mcgee-flutes.com/Visual_Analyser-Calibration.htm

Bob Griffin



Re: Find PC's Audio Out Voltage without CRO
On Sun, 24 Apr 2016 17:46:57 +1000, Bob Griffin

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Ok.  However, I don't think using software at the source is a good
idea.  If the stereo "front end" is that delicate, you might blow it
up just by turning on the PC and producing a glitch.  Or, some other
program might decide that it controls the sound card, changes all the
settings, and blows up your "frond end".  

Instead, I suggest an external hardware solution.  Not a meter, but
rather a limiter of some sorts.  I believe those can purchased, but
I'm not familiar with what's available.

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Nope.  None of the PC applications are reading the output voltage.
They look at the mixer voltage and measure that.  See:
<http://www.epanorama.net/documents/pc/soundcard_tips.html
and look at the block diagram:
<
http://www.epanorama.net/documents/pc/sb_mix.gif

The PC software only has access to D/A chip.  The A/D is for recording
and is not used for measuring signal levels.  It could be, as I
described where you use one channel to measure the output of another
channel, but it's usually not done that way.  

The PC knows what is going into the D/A converter and uses that
information to determine the output level.  If you could back feed the
low level audio output jack on the sound card with some audio, it
would not show up on any software VU meter program.  Only audio data
that goes into the D/A can be displayed.

From there, the audio goes to the "line" jack and also to the speaker
output.  The gain between the mixer and the "line" jack is known (I
think it's x1) and fixed.  The mixer gain is also known and fixed
(also x1).  With those numbers the "line" output level can be
calculated from the D/A levels.  

If you look at typical audio control, music, whatever audio software,
you never see a bar graph or meter showing the speaker output level.
That's because the speaker audio amplifier gain is purely analog and
of an unknown gain.  Therefore, its output level cannot be calculated
from D/A levels and the subsequent gains.  Note that the mixer is also
purely analog and has the same problem.

Therefore, the only numbers you can get directly for a playback VU
meter come from the D/A converter on the sound card.  They don't
measure anything (in playback) because there are no A/D converters
present (except for the audio input A/D which is not used in
playback).

Got it?

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--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Find PC's Audio Out Voltage without CRO
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a high efficiency red LED, or two antiparallel might be a good start.


--  
  \_(?)_

Re: Find PC's Audio Out Voltage without CRO
snipped-for-privacy@cybernode.com says...
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 if all you want is input protection, put two signal diodes or ones with
low CAP in seriels back to back across the input of the stereo.
  
 Most line inputs are ~ 0.650V rated, 1V Peak. The diodes will give you  
just over that for clamping..

 Also, you could use the center ties of the diodes to drive a Hi-Z  
LED circuit for overdrive indication.


Re: Find PC's Audio Out Voltage without CRO
On Sunday, 24 April 2016 18:58:55 UTC+1, M Philbrook  wrote:
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Put them in antiparallel. It won't work otherwise.

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Now they will. For lower voltage use schottkies.


NT

Re: Find PC's Audio Out Voltage without CRO
On 4/24/2016 11:06 AM, M Philbrook wrote:

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You might want to reword that so someone who doesn't already know what
you think you mean can figger it out.

While protection is good, that method will make the audiophools heads
explode thinking about nonlinearity.

Re: Find PC's Audio Out Voltage without CRO
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well I had a zener seriess limiter circuit in mind when I wrote that..

 Its obvious not going to work here, since I doubt we can get
zeners under a 1 volt, but I could be wrong there.  
  
 anyway..

 Two sets of series diodes back to front will give a compression of
~ 1.4 volts or so..

 of course two diodes back to front in parellel can offer some lower  
clamping protection being close to the threshold of the input level.

  
 As for the indicator using the double sets, you can tap from one of the  
centers as a reference to a LED over drive circuit.

 If pictures tells the story better I can supply that, too.

 To each his own I guess.


Re: Find PC's Audio Out Voltage without CRO
On Saturday, April 23, 2016 at 6:56:20 PM UTC-7, Bob Griffin wrote:
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Do you mean AC amplitude (averaged over many cycles), or do you intend
to record a peak value?

Either way, there's a large variety of measurement options.   At the crude
end, use a power amplifier and a waterproofed resistor, and see how long
it takes to boil away some water...
Then, your problem becomes that of relating 'half a liter boiled away in
seventeen minutes' to the level you wish to achieve.

For good reasons, most people use a meter.

Re: Find PC's Audio Out Voltage without CRO
On Sun, 24 Apr 2016 11:56:10 +1000, Bob Griffin

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Maybe this might work
<http://www.darkwooddesigns.co.uk/pc2/meters.html

But as stated here and on this website, you can feedback the output to
the linein to measure it.

Cheers

Re: Find PC's Audio Out Voltage without CRO
On Saturday, April 23, 2016 at 9:56:20 PM UTC-4, Bob Griffin wrote:
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No meter.. you mean I can't use a DMM?  

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