New Memeber, I have an idea and a question

[AnalogDude]

Hello all, I've been lurking around for a while now, and experimenting on my bread board. Now it's time to post. I recently bought a used analog oscilloscope and it seems to be working great, I've tested fuzz faces and a green ringer on it, both yielding what one would expect to see. The thing is I can't seem to get my head around the output of the shocktave. It sound good through my amp so there's no problem as far as I can tell, but on the scope it looks weird and the period of the wave is not doubled. If I had to assume whats going on it is the mad amount of distortion but I'm just wondering if anyone else has ever stuck a scope on one of these.

Now when I got my scope home I thought it was going to be good enough to play my guitar through an effect and see whats going on as far as clipping and such. It was too chaotic for me. That's when I decided I needed a sine generator. I didn't have components to build one and having just bought a scope I was out of options for a while... or was I? What about those online tone generators? If only I could get that tone into my pedal... Maybe i could mic my speaker with a piezo out of a telephone receiver... Maybe I could take the cord that runs from the right speaker to the left speaker, cut it and add alligator clips... Bingo! If you need a sine generator quick its the way to go. I'll upload some pictures when I get a chance to mess with the forum. I'll like the site with the tone generator if anyone wants it.

It just so happens that i didn't have to actually ruin my speaker cord, I salvaged a piece of an RCA cord that was a match to the output on the live speaker. A head phone jack might work too. The nice thing is the speaker (and computer) volume makes it possible to vary the amplitude of the signal.

If anyone has ever scoped a shoctave it'd be cool to hear your results. I'll upload a pic of mine.

Cheers for now

[AnalogDude]

^Fuzz, Green Ringer and Shocktave on my board^

^Heavy Fuzz^

^Mild Fuzz^

^Medium Fuzz^

^440Hz Sine wave via speaker^

^Green Ringer, "Shape" pot open^

^Green Ringer, "shape" pot closed^

^Weird Shocktave Wave, Med gain^

^Weird Shocktave Wave, Low gain^

^Weird Shocktave Wave, High gain^

^Who wouldn't play free bird through their new scope^

[Jdansti]

Welcome!!!

Sorry I cant answer your question, but cool stuff!

I need to check with my brother who has my Dad's old scope and see if I can "borrow" it. 

[PRR]

Turn-off the overhead light, or lay cardboard on the top of the 'scope to kill that glare. It's confusing the camera and giving poor image of the 'scope screen.

That's a dual-chanel 'scope. Take a tap off your "clean" source into Input A(*). Use Vpos to center that trace in the top half of the screen. Put your "dirty" signal into Input B. 'Scope mode A&B. Center the B trace in the bottom half of the screen. (Sync trigger probably A, but try other settings.)

Like this guy got a sine on top and a square (infinite fuzz?) on the bottom:



Another interesting (mind-expanding) display is XY. That gets A going left-right and B going up-down. If the "effect" is perfectly clean, the result is a slanty line. If the effect is a simple treble-cut, then as you change frequency higher the line turns oval and then flattens out. Simple fuzzes will be slanty up to a point and then flat-line (clipping). Crazy distortion may actually kick-back.

EDIT: (*) your 'scope calls 'em 1 and 2, not A and B.

[AnalogDude]

I only have one set of leads for the beast atm. The double trace is what it shows on the shocktave, notcamera magic
Thanks for the replies guys. My latest expirament is bouth octsves in parallel but I'm having issues balancing the outputs.
I'm at work so I'll blab more later

[Derringer]

these are pretty much what I see from the output of the shocktaves I've built
it's not doubling of the wave you're looking for like in an octave up, it's halving
and if yu use your imagination a bit, you'll see how that's happening in these ... keep in mind that the shocktave is nowhere near being a perfect octave down device so that's why there's so much other stuff going on in the images

[PRR]

> I only have one set of leads

Clip-leads (you ALWAYS need clip-leads!!). Now stick the end of a 1/2W resistor in Input 2 center hole. Put a red clip-lead on that. Put a green clip-lead on the edge of the Input 2 connector outer shell, or on the Ground post if the 'scope has one.

It's a little prone to falling out, but I've done a lot of work this way.

That's your Input 2 "probe". If you are working in the audio band, not over 5V or 10V, not way-way weak, then you do NOT need a special probe.

You might find a BNC connector BUT there are two kinds, with different size center pins. If you mix them up you stretch the inside contact in the 'scope connector, which is bad. Compare your 'scope probe center pin against anything else you think you might use.

> The double trace is what it shows on the shocktave, not camera magic

I know. The sync trigger is confused. Fiddle those knobs (I'd try trigger level or mS/cm) and it may clean-up, show one wave with an odd/even alternation. For octave-up, it sure would be better to feed the clean source and use it for trigger. Octave-down is always ambiguous and wants manual sweep adjustment.

[AnalogDude]

Cool. I Switched from "DC EXT ONLY" to "AC" Coupling which sounded like it may track better in my manual ( and thanks to you PRR). And I got the waves to separate. It seemed it was racing so fast to the left that my eyes were tricking me into thinking there was two traces. So can we assume that 1 period of a shocktave output is from one crested peak to the next crested peak, or one scalloped peak to the next scalloped peak, even tho it goes through two valleys first? It's a mind boggling experience haha.

And you are telling me I can use my clean signal to tell the dirty signal when/where to track? I have the manual here but its all greek(or should i say geek ) to me.

[PRR]

> It's a mind boggling experience haha.

"mind boggling".... when stoner friends, especially users of 3-letter drugs, hung around the lab giggling, I'd set up the FM radio and 'scope and keep them mind-boggle entertained for hours.

Yes, it's mind boggling in a different flavor just exploring all the things a 'scope can show you. Especially a 2-chan job.

> have the manual here but its all greek

You *may* glean something from good-old books.

http://tubebooks.org/technical_books_online.htm#Test & Measurement (equipment, instructions...)

Sicuranza will be a very basic introduction, because in 1938 they only had very-basic 'scopes. Rider is a bit older but he's often a good author.

Middleton is good for 'scoping audio.    

Haas should be a good mid-level 'scope book

Note: this site has been VERY slow for the last two days. Some leeches are probably sucking-down the whole site. Be patient, be kind.

[AnalogDude]

Thanks for the link. I'll have to check that stuff out over the weekend when i have time to really dive in. It seems I have an issue with the scope however.

The amplitude of the waves was changing on its own, even when hooked to "cal". Also the Vertical Position control was not functioning properly, if it moves the trace at all it returned to the midpoint slowly on its own. it seemed to stop doing it now but I was wondering if you might know why, or if I should expect the old dog to die. According to what I can gather, its an issue with the vertical amplifier, it was clipping on its own also I believe.

In a more forum related subject I seem to have gotten my octaves to blend in a parallel arrangement by feeding them both into a 741 based audio mixer (pretty much just an op amp) via a blend pot. I may replace the 741 with a fuzz because the octaves seemed to lose some edge anyways. I read about using filters and compressors and stuff to make this work smoother but I'm trying to learn so I have to do it the hard way haha.