Sinwave generated by computer

[Gabi]

Would this be helpful in case I would like to check the amp on a oscilloscope?

Or do I have to find an old school one?
What frequency should be used?

thanks...

gabi.

[Twigley]

I think you'd need to drop the voltage from a soundcards lineout, i'm not sure though. I think anything from around 100Hz up to 1000, or even 2000Hz. Plz correct me if i am wrong.


'old skool' lol like the valve sig. gen. i use at skool? it works dam well though, but it smells bad.

[MichaelJ1965]

you could mic the computer.... use whatever tone you want.

[Gabi]

thank ya all...

gab.

[zaphod_phil]

I've never tried doing this with a PC, but I have heard it can be done. You need to use a good cap to isolate your PC sound card. The standard frequency to use for most general audio work with a scope is 1kHz.

[Twigley]

You can buy a good sig gen. about the size of your average DMM for $60 maybe even less. An you could easily make one from a few SS components, for a specific output and with a small pot to change frequency.

[Gabi]

thanks Phil and Twigley!

Nik told me that there is a possibility that my oscilloscope might already have an in-built sine wave generator...
I'll have to check that... has many buttons and outputs...

Also once I have this set up... What kind of tests should I run? I'd like to take a couple shots and post them here.
Like distorsion harmonics visualisation? Any hints?

thanks all!

gabi.

[Twigley]

All sorts, i love CRO's, take some shots of the amp at full pelt, an just at the point where the peaks begin to round out. You could take some from various positions within the amp when it is up full, likeafter the first stage, just before PI, etc. Depends on the voltage rating of the scope really.

True alot of scopes i've seen have built in Sig gen.

As phil said the usual test point on guitar gear i have seen is to be about 1KHz but could experiment across the range to see the different results.

[bubba2]

Got no idea if this would work, never tried it but instead of a sig.gen.
what about having a friend strum a chord while you check the circuit
with a scope. Would that give a better indication of whats happening in the
circuit. I mean amps are made for guitars not for sig.gens.

[Twigley]

No that is the reason why you have to use a sig gen. With a scope you look at the sine wave. When you strum a chord there is not just one frequency you can see, there are 6, along with harmonics thrown in and other things. Even plucking a string wouldn't work because at the exact time you pluck the string there is a surge in output fromyour guitar and as it decays the signal gets weaker.

With a sig gen you get one frequency at one output level. This way you can observe it on the scope properly.

Woohoo hit my 100 post mark i am officaly obcessed.

[bubba2]

Twigley the obcessed,
Thanks for the info, I haven't got a scope and know nothing about them.
but now know I need a sig.gen as well.

[Twigley]

Twigley the obcessed,
Thanks for the info, I haven't got a scope and know nothing about them.
but now know I need a sig.gen as well.

Yeh sorry for the spelling, my spelling gets worse the more tired i am. Scopes are great instruments, and probly the best thing to use for measuring voltage, although not many peopleuse them for this.
I wish i could afford a scope, i only get to use them at school but if you are gonna get one make sure it is a dual scope as this is very usefull, any other features are a bonus for guitar.

[englishjim]

Somewhere I have a bit of code that I was using as a spectrun analyser. It can also show the wave form. The resolution is lower than an analogue scope, but I've always thought I should write a sig-gen / scope / harmonic analyser using this.

Oh, the point of this post was, given a small buffer circuit (and, I suggest, an isolating x-former) you could also use the pc as the scope as well.

James