Diode clipping sample clips.

[digi2t]

Hi all,

I've been feverishly working on completing my Insanity Box before I have to move (saving the shop for last!), and I want to incorporate a clipping diode multi-selection switch of some sort. I'm still a bit up in the air as to whether it will be a simple A/B, sym./asym., footswitch arrangement, or, a 4 position rotary affair. I'm leaning more towards the rotary job, since foot-switching diodes in mid song might produce an undesirable popping sound.

In any case, I was thinking that I would have to do some trials insofar as sound was concerned, when I came across this "Diod0rama" mp3. This guy was nice enough to record a run of various diode clipping configurations back to back, giving you a taste of each tone. The clip link is http://www.box.net/public/xa79ot2xuf, and the list is as follows;

0:00 - 0:10 : Clean (no pedal)
0:11 - 0:24 : 1N4148 silicon pair (symmetric; TS-808 stock)
0:25 - 0:36 : 1N4001 silicon pair (symmetric)
0:37 - 0:49 : 1N34A germanium pair (symmetric)
0:50 - 1:03 : 1N4148/1N34A (asymmetric)
1:04 - 1:16 : Red LED/1N34A (asymmetric)
1:17 - 1:28 : Red LED pair (symmetric)
1:29 - 1:42 : Yellow LED pair (symmetric)
1:43 - 1:55 : Yellow LED/1N4148 (asymmetric)
1:56 - 2:10 : 1N4148/2x1N4001 (asymmetric; clipping option included in BYOC Overdrive kit)

Credit for this goes to V!N, over at mylespaul forum. According to his post, the circuit is a Tube Screamer. He doesn't state what type of amp is used, but the clip most definitely gives you a fairly good picture of what to expect with certain combinations of diodes.

Cheers,
Dino

[ayayay!]

:04 - 1:16 : Red LED/1N34A (asymmetric)
1:17 - 1:28 : Red LED pair (symmetric)
1:29 - 1:42 : Yellow LED pair (symmetric)
1:43 - 1:55 : Yellow LED/1N4148 (asymmetric)

Unless one color is clear, these two pairs will sound the same.  Red, yellow, green, 3mm, 5mm, etc... If they're all diffused they're going to sound identical. 

[digi2t]

Is there much of a tonal difference between clear and colored LED's? I know it can be somewhat subjective, but if you've tried them, what's your impression?

[anchovie]

Unless one color is clear, these two pairs will sound the same.  Red, yellow, green, 3mm, 5mm, etc... If they're all diffused they're going to sound identical. 

How so? Check some datasheets - the Vf specs speak for themselves.

[merlinb]

How so? Check some datasheets - the Vf specs speak for themselves.

Actually they will sound identical, you just need to make the signal bigger/smaller to get thesame amount of clipping depending on the diode type. The shape of the diode curves are still basically the same.

However, the fact that you need more/less gain to get the same clipping, may cause a tonal change somewhere else in the circuit. (e.g., opamp slew limiting)

[ayayay!]

How so? Check some datasheets - the Vf specs speak for themselves.

Right.  Forward voltage for almost all diffused LEDs is typically only 1/2 or 2/3's of what they are in the ultra-bright clear LEDs.  So for instance this is 2.2V  http://www.chml.com/products/pdf/1-78.pdf  and this is is 3.5V.  http://parts.digikey.com/1/parts/682900-led-3mm-blue-water-clear-521-9918.html

If we're talking the example given originally, then yeah I'll put my money where my mouth is:  They'll sound the same.  Sure enough, from 1:17 to 1:42, there's no difference.  1:04 -1:16 sounds just like 1:43 - 1:55.   

[anchovie]

Right.  Forward voltage for almost all diffused LEDs is typically only 1/2 or 2/3's of what they are in the ultra-bright clear LEDs.  So for instance this is 2.2V  http://www.chml.com/products/pdf/1-78.pdf  and this is is 3.5V.  http://parts.digikey.com/1/parts/682900-led-3mm-blue-water-clear-521-9918.html

That's a difference between the properties of standard and ultra-bright die, the package they go in is coincidental. You'll still get slightly different Vf between colours in diffused packages, so in theory at the same gain setting they'll clip at different thresholds. I agree that it's all down to ears at the end of the day, though!

[teemuk]

Actually they will sound identical, you just need to make the signal bigger/smaller to get thesame amount of clipping depending on the diode type. The shape of the diode curves are still basically the same.

This. And whatever difference you have in curve shapes you can compensate by introducing series resistance to the diodes.

[vendettav]

acutally nice clip