Clipping diodes

[Locrian99]

I've been playing around a bit with different clipping diodes.   Mainly soft clipping but there are so many different germanium diodes out there and they aren't exactly super cheap to buy a ton of different types to experiment with.   Curious on thoughts here, and I'm sure there's some conflicting thoughts on the subject.   But would you say the clipping sound is based purely on vf/leakage/type and actual part #doesnt matter.   Does the type matter?   Would a germanium coming it at 500mv vf sound the same as a silicon at 500 vf.   Thanks.

[antonis]

https://www.electrical4u.com/reverse-recovery-time-of-diode/

[Locrian99]

https://www.electrical4u.com/reverse-recovery-time-of-diode/

Alright that's a bit to wrap my still very green head around.   So essentially if I'm understanding it correctly signal will not be being clipped for a period of time based on the reverse recovery time of the diode.   So a 2n270 with a vf of .290 if it has a higher recovery time will clip less than a 2n276 with the same vf but a lower recovery time?

[antonis]

Quite right but, for audio work, it makes no difference..

Typical diodes recovery times are about 150 - 200 ns so they should matter for frequencies of about 5MHz..

[Locrian99]

So as frank would say the crux of the biscuit is it's all about the vf?

[MikeA]

So as frank would say the crux of the biscuit is it's all about the vf?

If you extend the discussion beyond Si and Ge diodes, and include LEDs, IMHO there's an audible difference in the trail-off of a 1.2V LED vs. 1.2V worth of diodes in series.  I find that LEDs invariably have an annoying fizz at the end of a note that's not present with Si or Ge diodes.  So when I need a clipping Vf in the 1V range or higher, I usually stack diodes or add a series resistor instead of using LEDs.  I don't understand the mechanism, just reporting my experience.

[Locrian99]

So as frank would say the crux of the biscuit is it's all about the vf?

If you extend the discussion beyond Si and Ge diodes, and include LEDs, IMHO there's an audible difference in the trail-off of a 1.2V LED vs. 1.2V worth of diodes in series.  I find that LEDs invariably have an annoying fizz at the end of a note that's not present with Si or Ge diodes.  So when I need a clipping Vf in the 1V range or higher, I usually stack diodes or add a series resistor instead of using LEDs.  I don't understand the mechanism, just reporting my experience.

Interesting, I have ts style pedal I built with symmetrical red leds as one option and noticed something similar.   I suppose I should've mentioned what really brought up the question beyond it being something I have somewhat wondered before, I had purchased some 1n270's from a vendor and they showed up today and they look like 4148's or any other silicon diode.   However the couple I tested were all right around 280mv vf.   So I was curious if they weren't true germanium does it really matter.    I also have another project I'm currently working on the original calls for a 1n270 in series with a 1n4148, I have some high vf 1n34as was wondering if I could do the 1n34as and expect the same results since the vf would be similar. 

[GibsonGM]

Most likely, your results will be the same, yes     In this case (not VHF or microwave or anything), what really matters is the Vf.   If it's nearly the same, well then, off you go!    Most designs are not so critical that you'll suffer by this kind of substitution. 

[MikeA]

... I had purchased some 1n270's from a vendor and they showed up today and they look like 4148's or any other silicon diode.   However the couple I tested were all right around 280mv vf.   So I was curious if they weren't true germanium does it really matter.

With a Vf around 280 mV, they could be either Ge or Schottky.  Personally, I find it difficult to hear the difference.

...I also have another project I'm currently working on the original calls for a 1n270 in series with a 1n4148, I have some high vf 1n34as was wondering if I could do the 1n34as and expect the same results since the vf would be similar.

To my ear, as long as the Vf adds up, the results sound pretty much the same, with the exception of the LED fizz I mentioned earlier.  +1 to GibsonGM, it takes a pretty big change in Vf to be audible unless you're doing A/B comparison.

[Locrian99]

Makes sense.  That pretty much answers my question just worry about the vf and less so about the type of I'm just trying to mimic something.    Thank you all.

[Steben]

... I had purchased some 1n270's from a vendor and they showed up today and they look like 4148's or any other silicon diode.   However the couple I tested were all right around 280mv vf.   So I was curious if they weren't true germanium does it really matter.

With a Vf around 280 mV, they could be either Ge or Schottky.  Personally, I find it difficult to hear the difference.

...I also have another project I'm currently working on the original calls for a 1n270 in series with a 1n4148, I have some high vf 1n34as was wondering if I could do the 1n34as and expect the same results since the vf would be similar.

To my ear, as long as the Vf adds up, the results sound pretty much the same, with the exception of the LED fizz I mentioned earlier.  +1 to GibsonGM, it takes a pretty big change in Vf to be audible unless you're doing A/B comparison.

I agree alas.... high gain sounds great with LED. The decay much less...

[Vivek]

Many brothers wrote that what matters for a clipping diode is Vf


I had written earlier and posted some graphs with two theories

Theory 1

what really matters is the ratio of

Vpeak in case the signal was not clipped
________________________________________
Vf


Which tries to imply 6 Volt signal clipped at 0.6V will sound similar to 3 Volt signal clipped at 0.3V will sound similar to 16V signal clipped at 1.6V



Theory 2

Different diodes reduce the volume to their Vf and most people dont normalise the output after that. They test each diode at different final volume.


Which tries to imply 6 Volt signal clipped at 0.6V and then amplified to 1V

will sound similar to 3 Volt signal clipped at 0.3V and the amplified to 1V

will sound similar to 16V signal clipped at 1.6V and then reduced to 1V



Which all seems to imply:

If you use many different clippers
and normalise the clipping percentage
and normalise the final volume

They will all be near identical.




Most DIYers try to plug in different diodes into a fixed circuit with fixed unclipped Vpeak at the clipping point and fixed gain after it. Hence changing diodes changes the clipping percentage and the final output volume.  They wrongly feel that the changes caused by different clipping ratio and different volume are actually characteristics of the clipping diodes.

But if they breadboard a circuit that allows them to normalize clipping percentage and final volume across lots of different clipping diodes, the DIYers might have a different impression.



Here's a photo of two dogs who played in the same mud pool (mud pool not normalized to dog height) :




And here are dogs sent to play in different mud pools that were normalised as per dog Height :




and now the height of the dogs was normalised after they played in the normalised mud pools:

[Steben]

In a clipper to ground the resistors whether series or shunt are very present in the result. A silicon diode with some resistance added sounds very much like a germanium if the V peak is adjusted. The series resistance of the signal plays as well.