[sdiy] first oscilloscope help

[Tom Wiltshire]

Nate,

On 13 Jan 2009, at 16:17, Nathan M. Reeves wrote:
>
> By the way i have been meaning to ask if 2x 15MHz is enough  
> bandwidth for most (if not all) synth DIY?
>
> I dont have any micro pics or anything (yet?) just want basic  
> voltage measurements and something with the ability to help me  
> troubleshoot.

I agree with Alan. For analogue audio, 15MHz is fine. I use a cheap  
dual trace 20MHz Instek scope that came out of a school technology  
lab, and it's fine.

> My idea is to hook up audio outputs to my scope channels....for a  
> SCOPE DJ SET at the local artsy fartsy venue (in atlanta this is  
> call eyedrum http://www.eyedrum.org/)
>
> I assume this would be ok as long as the impedance of the cable is  
> ~50 OHM, roughly the same as the probe

For audio use, don't worry about cable impedance. I've made up a  
couple of scope leads with quarter inch jacks on one end and BNC  
connectors on the other. I think I used cheap microphone cable. They  
work fine for what I needed them for (watching the input/output from  
stompboxes).

> Can I hookup both and to CH1 and CH2 and get some neat graphics?   
> or lissajous curve traces?

Lissajoux figures are generated by having sinewaves of different  
frequencies fed into the two inputs. You'd get a similar but more  
mangled effect by feeding two different audio sources into the two  
inputs. Two separate synth oscillators would probably be good though.  
Try it and see.

T.