Test Equipment: Oscillocopes

[Brian516]

OscilloFUN!     

https://www.youtube.com/watch?v=YUlk-zwKfWo

Looks a whoooooole lot better now!
Hooked up a pair of old active PC speakers instead of the headphones, so you can actually hear it on the vid, too.

Other than being 90 degrees off, it looks like it should!

[picowatt]

WELP....


Thanks TK for telling me to slow down, and PW for telling me to start back at square 1.  When I combined both pieces of advice, I solved the issue...

It appears that my PC wasn't actually disabling the enhancements when I was telling it to, for some reason or another. So it was the "Loudness Equalization" enhancement that was causing all the trouble.  I guess when I split up the HP jack and the main internal speakers, it disabled my ability to change those settings, even though it let me check/uncheck boxes and hit OK....  stupid computers.

https://www.youtube.com/watch?v=GKLZJ8hCClY
At 0:28 I say "microphone" when I meant Headphones.

Simple problem, simple fix.  Now to figure out WHY my laptop didn't change the HP settings with dual outputs enabled!! (or maybe it even had something to do with me shutting off the PC for a few min, and then powering it back on... who knows.... maybe I didn't restart after installing Soundcard Scope, and it froze my audio settings?
my bet is that it had something to do with the restart, and I won't be able to get it to freeze my settings again.)

Sooooooo..... NOW to see if I actually see the proper visuals for Youscope & Oscillofun!!! ANNDD  I can probably listen in, too!

Thanks for the always-good-advice, everyone!

Brian

I should have remembered this little trick from my PC repair/programming days..... if there's an issue and it involves a computer - RESTART THAT SUCKER FIRST!!!!  hahha

Brian,

Looks like you are getting a stable display!!

It appears that you have stumbled upon one of the handy uses for a 1K square wave and a scope when doing audio testing.

A 1K square wave contains harmonics.  A perfect square wave would contain an infinite number of harmonics, but for audio work, we usually figure the leading edge of a 1K square wave will let us see out to 10K, and that a 2K square wave will let us see out to 20K.

If you feed a 1K or 2K square wave into an audio system and adjust its equalizer (tone controls) at various frequencies, you can rapidly tell if the equalizer is working.  For instance, a treble control when boosted, will create a peak at the leading edge of the square wave as the level of the higher frequency harmonics is increased (similar to the large peak at leading edge of the square wave in your video).  Cutting the treble control will cause the leading edge of the square wave to droop, or round, as the high frequency harmonics in the square wave are reduced.

A midrange tone control will produce a hump or dip in the middle of the square depending upon whether it is boosted or cut respectively.  A bass tone control will generally produce a left to right upward or downward slant of the square wave if boosted or cut respectively (sometimes you need to reduce the square wave to 100 to 500 Hertz to see the effects of a very LF equalizer that is centered at 50Hz or lower).

In your video, it looks like the high frequencies are being boosted quite a bit when your "enhancements" are turned on.  Any audio played thru that setting would sound VERY bright.

A "loudness" control typically boosts the bottom end (low frequencies) of an audio signal (as well as some upper mid boost).  Usually the lower the level control is set, the greater the bottom end is boosted when "loudness" is selected.  Your waveform looks more like just high frequencies and upper midrange are being boosted.  Possibly selecting a 100Hz square wave will allow you to see if the extreme LF is also being boosted, which would be indicated by the square wave tilting upward from left to right.   

Try to ensure that all EQ and "enhancements" are turned off when using the PC FG so that the waveforms will look correct (flat frequency response thru the soundcard).

I sure like seeing your waveform lock right up when you tweak the trigger level control.

You're getting there...

PW

[TinselKoala]

OscilloFUN!     

https://www.youtube.com/watch?v=YUlk-zwKfWo

Looks a whoooooole lot better now!
Hooked up a pair of old active PC speakers instead of the headphones, so you can actually hear it on the vid, too.

Other than being 90 degrees off, it looks like it should!

That's great! It's actually one of the best displays of that file I've seen! This is actually the first time I've been able to see the full  A T O M D E L T A letters so clearly, even if they are upside down (instead of sideways?)  You could try inverting CH2 and see if the letters show right-side up!

Clearly there is nothing wrong with the major sections of the scope: input and display. I doubt that there will be any issues with timebase or trigger either.

You've got the L and R channels going to the wrong scope channels is all, just swap them and you'll see the display rotate 90 degrees to conform to what is usually seen. But before you do that try inverting CH2 !

[TinselKoala]

Brian, in the earlier video you are puzzled by the fact that at one point the scope still showed a horizontal line when you had no signal from the laptop going to it. Later on, the screen blanked when you had no signal. What was the scope control that you adjusted between those incidents? The scope's Trigger Level control. 
When it didn't blank, you had the trigger level set so precisely that it responded to the inevitable tiny noise left on the signal and showed you the baseline. Moving the control a tiny fraction either way would have caused the screen to blank. When you reset the trigger level later on, you didn't hit this exact setting, so when you turned off the signal from the soundcard the screen blanked as you expected it to. That all actually indicates _great_ trigger performance from a very sensitive trigger circuit.

[picowatt]

Brian, in the earlier video you are puzzled by the fact that at one point the scope still showed a horizontal line when you had no signal from the laptop going to it. Later on, the screen blanked when you had no signal. What was the scope control that you adjusted between those incidents? The scope's Trigger Level control. 
When it didn't blank, you had the trigger level set so precisely that it responded to the inevitable tiny noise left on the signal and showed you the baseline. Moving the control a tiny fraction either way would have caused the screen to blank. When you reset the trigger level later on, you didn't hit this exact setting, so when you turned off the signal from the soundcard the screen blanked as you expected it to. That all actually indicates _great_ trigger performance from a very sensitive trigger circuit.

TK,

Do you know if AUTO on Brian's TEK allows the scope to free run (display a trace) in the absence of a trigger (signal input)?

If so, he might be more comfortable using that mode instead of NORM.

PW