Osciiloscope

[Austin73]

Just been offered a cheap oscilloscope from a friend, just wondered what the benefits of one would be to making fx. Any suggestions and advice greatly appreciated

Cheers

Austin

[RedHouse]

You can gain great understanding into what circuits are actually doing by using an Oscilloscope.

[Coriolis]

Yep, as I understand it, you can (if you have a dual-trace scope) simultaneously see the signal you send through an fx-box and see what it looks like when it comes out. Handy!

C

[Pushtone]

FWIW
Jack posted this free software O-scope back in Feb.

http://www.diystompboxes.com/smfforum/index.php?topic=41994.msg303172#msg303172

[jrem]

FWIW
Jack posted this free software O-scope back in Feb.

http://www.diystompboxes.com/smfforum/index.php?topic=41994.msg303172#msg303172

what does one do for probes on that?   using the soundcard would indicate the 9pin din connector for an input, or a mic in . . .   no reference on that website as to inputs . . .   anyone know?

[Noplasticrobots]

An oscilloscope provides no use for effects. That being said, send it to me instead. I'll have a look at it. 

[Peter Snowberg]

If a picture is worth 1,000 words, a live scope trace is worth at least 10,000,000. 

[sta63bmx]

NFS.  Without a scope, you have to rely on "hearing" what the circuit is doing, or on steady voltage/current/resistance readings in a circuit.  With a scope, you can SEE what is happening right now, on a smaller timescale than is possible with anything else.  You really need to have two channels simultaneously (imo) to make use of a scope, but the soundcard one does it!  That's just awesome.  You could build a breakout box that would leave your hookup just like the front of a real scope, and then you could use 10x probes, whatever. 

That scope is way too slow for RF work or fast signal work in a lab, but it's WAY more than enough for audio frequency stuff.  On the off-chance that you can hear a 20 kHz signal (ha!) it should be able to sample at least 4x that fast, probably.  Kinda rough, but that's only on the way high end.  You guitar signals, which probably cut off around 4 kHz, are being sampled at least 10x faster than their own frequencies.  That's about 5x better than the Nyquist bidness, so that works for me!

As far as probes, I didn't see it written out, but I'm sure it uses the left stereo channel as one scope channel, and the right stereo channel as one scope channel.  So you would bring a stereo cable out from your computer, and then just build a simple breakout box where you have "left" and "right" jacks, where the left channel might be channel A, right channel might be channel B or vice versa.  You could use BNCs or audio jacks or whatever.  I would use two BNC jacks (amphenol makes plastic bodied ones that will set you back maybe $1.50 a pop, at least as cheap as switchcraft, or salvage them from a component video piece of equipment).  I woudl recommend BNC because then you can use nice shielded BNC cables (pretty cheap) and you can get grabber plugs, nice probes, everything you'd use with a real scope.  Just build the "front panel" in a cheapo little Radio Shack box or whatever and run the software on a beater PC on the off-chance you smoke it doing something goofy.

I'll tell you this, my $4K Tektronix in the lab doesn't have a spectrum analyzer!!!  It doesn't double as a function generator, either.  You could run your FX input from the function generator and pick up the output on the other channel.  That is t3h fr34k1ng w1n.  Why do people donate stuff like this to the rest of us for free?  Crazy.

EDIT: I'm so dumb!  THe function generator output is on your audio out, surely.  So both scope channels are still free.  That's like having a third arm or something.  Unbelievable.  THis is a good excuse to buy a wireless router and build a beater PC.  I could replace my scope AND function generator on the bench while adding access to all schematics on the net, my email, and having my HP calculator emulator and...and whatever!  And I'll miss you most of all, Scarecrow.

[WildMountain]

I have absolutely no experience with oscilloscopes, so bear with me...
I must say, the software looks very nice, and I would like to try using a scope in pedal building (although I would have to do a lot of learning for that). What isn't clear to me is what the probes are/look like and how to connect them to my PC. Sorry sta63bmx, your post is way above my head.
Does anyone have a pic of their setup (using PC scope)? A pic says more than a thousand words...

[jrem]

As far as probes, I didn't see it written out, but I'm sure it uses the left stereo channel as one scope channel, and the right stereo channel as one scope channel.  So you would bring a stereo cable out from your computer, <SNIP>.  Just build the "front panel" in a cheapo little Radio Shack box or whatever and run the software on a beater PC on the off-chance you smoke it doing something goofy.

Unacceptable answer.  You'll let the magic smoke out of the sound card the first time you put +12vdc to it. 

[Peter Snowberg]

The codec on the sound card is already AC coupled so your best bet for a cheap-o probe would be to grab a big metal film cap like 1uF, connect one side to your probe tip, connect the other side of the cap to a little resistor like a 1K, and connect that to your audio input. Now place a low voltage zener diode from the resistor/soundcard connection to ground with the anode connected to ground. The diode voltage should be LOWER than 5V. 4.7V is fine and a little lower voltage is better.

The cap prevents any DC from flowing through your probe, the resistor limits current if you do get a lot of AC flowing, and the zener clamps the maximum voltage that your sound card will see to a fairly safe range.

[WildMountain]

Is this the way you guys do this, or do you only use "regular" scopes? Maybe I should look for one on Ebay?

[Dave Eason]

I like the new LCD scopes with the FFT feature, spectrum plots are great to look at what harmonics are being added or taken away etc.  I'm looking for a cheap Tektronix on ebay right now... [laughs!]

[Hal]

I like the new LCD scopes with the FFT feature, spectrum plots are great to look at what harmonics are being added or taken away etc.  I'm looking for a cheap Tektronix on ebay right now... [laughs!]

I've been using a LeCroy564a.  I've grown to like that :-D.  I think it can do math stuff.  I highly recomend buying one .  Buy one for me too, while you're at it.  Screw Tek lol.

[RaceDriver205]

Magic smoke indeed. One of my lecturers was ranting on about how Op Amps have a little man in them who looks at the two multimeters attached to the + and - and alters the output 'knob' accordingly. He also said something like the man wont do his job if his magic smoke escapes...

I dont know about magic, but he's been smoking some serious s~!t.

Oh, and get the Oscilloscope. If its cheap its well worth it.

[Dave Eason]

[/quote]
Screw Tek lol.
[/quote]

ahh, i really want an Agilent, but that aint ever going to happen unless I win the loto