low-end scope

I used to get up before dawn to go to the Foothill flea market, but ebay kind of killed it off. One met personalities there... Jim Williams, Bob Pease, Peter Alfke.

John

audio.

The digitals have pixels and adc quantization, but the difference re: an analog scope is more psychological than real. If you use signal averaging, a digital scope will pull signals out of noise as no analog scope can.

I own about 60 oscilloscopes and can take my pick. 99% of the time it's digital. And by our standards "audio" is crude.

John

I had a few HPs that had electron flood guns, ditto. But I never much liked HP scopes. We demoed one HP digital scope that had, like, 4 buttons on the front panel. Nobody could figure out how to get it to work.

John

On a sunny day (Tue, 02 Mar 2010 07:02:41 -0800) it happened John Larkin wrote in :

:-)

audio.

That is why I would like some *cheap* spectrum analyser.

:-)

for audio.

It is in the sense that no audio signal has anything like the s/n to justify a 24-bit ADC or DAC, even if a real 24-bit part existed. And the idea of even 12 bit linearity is silly when you are using microphones, power amps, loudspeakers, and signal trains that deliberately add distortion.

But if I have 1 PPM of hum or DC offset in my NMR coil drivers, or 100 PPM pos/neg asymmetry, users *will* complain.

And how does an analog scope work better than a digital scope when testing a 24-bit DAC?

John

I have one crt analog/digital that I would absolutely hate to be without. Hameg was one of the remaining makers of combinations. You need a at least 10 bit vertical resolution,

greg

One thing those DSO will rarely do is this: Hang the scope probe onto a node in the amp, touch this that and the other thing and see if there is a pulsating wee fattening of the trace in one little spot because of a crossover oscillation that the designer had missed.

The Instek here is a bit better than that, but still, it can't replace the analog scopes.

On a sunny day (Tue, 02 Mar 2010 08:17:55 -0800) it happened John Larkin wrote in :

Yes, and the brain has ways of removing unwanted noises. Personally in my place the environment noise would make 8 bit audio sufficient in many cases. I have runs tons of stuff through companders. Only late at night I would need 16 bits...

OTOH the ear (or our hearing) is very much logarithmic, so we hear distortions even in very low volume passages.

To reformulate the question: How are you gonna look at such a signal with an 8 bit ADC as in your scope? By putting some analog gain up front?

I've noticed that scopes with 640x480 or higher resolution LCDs tend to look much "better" than the lower-cost ones that are only 320x240, as the pixels are much more obvious in such a case (assuming a 5" or so LCD, that is).

audio.

Probably a TDS200 series. There are noisy as hell.

The one that glows is a Tek 7704A mainframe. When I need to go back to the office at night to pick up a document and it's pitch dark there is this eerie blue glow from that CRT.

2. > >> >> Or something like that. Any suggestions or comments?

Ah yes, Bob Pease selling his book out of the boot of his VW. Those were the days.

I got my Tek 11402A at Livermore two years ago for $250. Nobody would pay to ship that beast. The problem with DeAnza and Livermore is you need to go often, and often there is nothing but junk. Livermore is this weekend, provided the site isn't too muddy.

in many cases.

I do have a Tek AM503 that I sometimes use to front-end a digital scope. It's a differential amplifier with switchable gain to 100K, DC offset, and switchable low and high cutoff frequencies. Its overload recovery is better than most any current-production analog or digital scope can achieve.

John

On a sunny day (Tue, 02 Mar 2010 11:53:29 -0800) it happened John Larkin wrote in :

in many cases.

Nice knobs! That is the kind of controls that I like :-)

:-)

for audio.

Watch out for 40/80kHz conductive noise leaking out of its backlight inverter. Those things were IMHO a disgrace to Tektronix.

:-)

audio.

My usual scope is a TDS2012. It shows a little trace noise, but it doesn't bother me. An analog scope trace would be as fuzzy, unless you use an old 547 with a two-foot-long CRT.

Analog scopes just aren't quantitative like digitals are:

ftp://jjlarkin.lmi.net/RTD_in_air.JPG

Of course, audio isn't quantitative.

John

:-)

for audio.

Try to see stuff like weak and sort-a demodulated cell phone fuzz on a large analog signal. That's where analog scopes really excel. OK, you have to darken the romm, but so what?

Me, too :-)

Most DSOs such as mine come with a battery option. I didn't order that but AFAIK it runs several hours on a charge.

rkin

rees :-)

se for audio.

Yeah!! signal averaging is great for getting good signals from a digital 'scope. I wish our 200MHz Tek had more than 128 averages. (Trigger on the top of a noise signal and you can pick out all sorts of coherent crude.)

George H.