Is there any noticeable difference among silicon diodes?

[antonis]

Man.....wish i could knew how to work an o-scope.  anyone want to give some lessons?? LOL

All you have to do is familiarize yourself with the meaning of "Probe Insertion"....

[Digital Larry]

I thought that 1N4148 was "faster" than 1N400X series...
(unless you've altered measurement frequency..)

What you're looking at there is not the "fastness" of the diode.  At the top of the peak, you're mostly seeing forward voltage differences and the steepness of the cutoff.  The "ideal diode", which doesn't exist, but is occasionally described for ease of interpretation, brick-walls at the turn on voltage and would give you a square wave in the test circuit.  Those would suck for making guitar distortions!

The speed biznis happens as you transition from forward bias to reverse bias and depends on how quickly charge carriers can be cleared out of the junction.  As I recall this has to do a lot with the capacitance of the junction, which is why smaller (lower current carrying) diodes are usually faster than ones made for carrying higher currents like the 1N400x series.

Please note that the shelf life of this info (my brain) is probably expired.

[antonis]

At the top of the peak, you're mostly seeing forward voltage differences and the steepness of the cutoff. 

I presumed that the more flat peak corresponds to the faster diode by means of obtaining the forward voltage in shorter time..
(which also reflects on the recovery V/t curve..)

[R.G.]

Audio signal speeds are so very slow compared to diode cutoff times that this isn't an issue.

For some interesting results on diodes, try inserting a small resistance in series with the diode.

[antonis]

For some interesting results on diodes, try inserting a small resistance in series with the diode.

Meaning for results other than raising the clipping level..??

[Groovenut]

Inserting a resistance in series with the diode "rounds" the clipped waveform more, softening the clipping.

[Groovenut]

I did a quick setup up of diode sets for comparison. I used 7.5 VAC RMS for the signal and snapped some pics of the waveform.

1N4148 Tayda



1N4002 Tayda

I thought that 1N4148 was "faster" than 1N400X series...
(unless you've altered measurement frequency..)

No altering of frequency. The only thing I changed was relocating the Y axis to compensate for the forward voltage differences in the diodes, thus making the peak appear in the same place on the screen.

[R.G.]

For the beginners, it's also useful to read "Distortion 101" at geofex. I notice that it needs a good editing, as I've learned some things since then too, but
diodes and clipping haven't changed a whole lot in 22 years.
http://www.geofex.com/effxfaq/distn101.htm