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previous: Benjamin Fargen To all,Can anyone steer me ... -- 7/19/1999 4:14 PM View Thread

Re: Oscillocope questions???????

7/19/1999 5:52 PM
Carl B.Re: Oscillocope questions???????
For guitar amps, anything above say 10Mhz operation is just fine, but expect to pay more for more megahertz. I say 10Mhz, because with that you can catch most of the ultra-sonic high-freq oscillations that your high-gain Soldano knock-off is probably exhibiting. A 1Mhz scope wouldn't have those oscillations show up.  
 
 
 
Instead of going much above 10Mhz though, consider putting money into neat features like dual trace (allows comparison of input to output of a circuit simulataneously), or even digital if the bucks permit.  
 
 
 
Analog is just fine for guitar amps. You use a frequency generator to drive the circuit, an analog scope locks onto that beautifully, giving you a seeming "snapshot" of the waveform. Tried and true for decades. Digital is just able to give a *real* "snapshot" right after the triggering event (which is either given level of the input signal or a finger-on-the-"trigger-now"-button). And some digitals allow output through a serial port to PCs for analysis and printout.  
 
 
 
Variable delay is a neat feature for looking at digital circuits, it allows you to look at small portion of the signal some precise time after a trigger event. But it doesn't work out to being very useful for guitar.  
 
 
 
The old tube scopes can be bargains, but buy one from a reputable source with a warranty unless its dirt cheap *and* you can verify correct operation before you buy. Since you don't know how to verify ops yet, just stay with reputable sources on those. Some of the old Tektronix and HPs operate beautifully and are very affordable.  
 
 
 
The newer solid-state models are pretty maintenance free. This is the one place where solid-state can coexist with my workbench. Well, that and my voltmeters. But dang it, my freq gen and cap checker are all-tube Heathkits!  
 
 
 
Something nice with the most newer ones (digital or analog) are the on-screen cursors. You set up the screen signal you want to capture, then adjust vertical cursors to get a voltmeter like reading the difference in voltage between the cursors, and adjust horizontal cursors to get readout of either the milliseconds or conversely the hertz of signal.  
 
 
 
Make sure the thing comes with probes, and that the probes have their "lead grabbing" tops with them. 1X, 10X are probes are a must. If no probes, figure an extra $20 each on up for new scope probes.  
 
 
 
That's about it. I found a solid state Beckman 10Mhz dual-trace for $75 at a pawn shop. Very nice, with dual trace and cursors, and not a single problem for the 4 years I've owned it.  
 
 
 
- Carl B.  
 

 
Replies:
Benjamin Fargen Carl, Thanks for the gr... -- 7/19/1999 6:50 PM
jt My grandfather just gave me an old ... -- 7/20/1999 7:41 AM