Asymmetrical clipping

[mrmet5]

Hi,

Is it the same asymmetrical clipping when you use only 1 diode, instead of 2-1, 3-1, 3-2, etc.? I tried it but I couldn't really tell the difference between 1 diode and 2-and-1 combination. I suppose an oscilloscope would be pretty helpful in a situation like this..

[Steben]

Hi,

Is it the same asymmetrical clipping when you use only 1 diode, instead of 2-1, 3-1, 3-2, etc.? I tried it but I couldn't really tell the difference between 1 diode and 2-and-1 combination. I suppose an oscilloscope would be pretty helpful in a situation like this..

Depends completely on what one percieves as difference and what circuit is around the diodes.

[Lino22]

It also depends on a signal strength. If you want to hear 2/1 si diodes, the signal swing must be above about 1.4V.

[mrmet5]

Ok I was asking more in general, but I see. Thank you guys! Back to the breadboard..

[antonis]

For a single diode clipper, one part of signal waveform should retain its amplitude..

[Mark Hammer]

When both diode orientations are used, in an "asymmetric" form, both half-cycles are constrained, with one half cycle more than the other.  How asymmetric the result turns out to be is a function of the difference in forward voltage between the two possible paths.  That does not have to be two different numbers of diodes.  For example, one Schottky and one red LED, back to back, would yield VERY asymmetric clipping because the LED has a forward voltage 8-10x that of a Schottky diode.

But there's asymmetry of clipping, and asymmetry of amplitude.  If I have a 2+1 diode complement, but crank the living daylights out of the signal, ahead of those diodes, then both half-cycles will be equally clipped and squarish, but one "side" will be at a higher amplitude/output-level than the other.

Fundamentally, the whole notion of asymmetric clipping, via diodes, rests on the strategic use of gain, in relation to diode conduction.  For my part, much of the appeal of discrepant diode sets is really more the increase in output level one gets from it, by lifting the ceiling on one half cycle, and the slightly greater dynamic range (i.e., ability to get cleanish tones when picking softly, with dirtier tones when you pick hard), instead of the more dynamically compressed sound of fewer diodes or use of those with lower forward voltage.

[ElectricDruid]

For my part, much of the appeal of discrepant diode sets is really more the increase in output level one gets from it, by lifting the ceiling on one half cycle, and the slightly greater dynamic range (i.e., ability to get cleanish tones when picking softly, with dirtier tones when you pick hard), instead of the more dynamically compressed sound of fewer diodes or use of those with lower forward voltage.

+1 agree. This is an excellent point. The asymmetric diodes give you some clipping at lower levels, and then a bit more when you dig in. This is often exactly what we're after (though there are lots of potential ways to achieve this, clearly). The tendency towards some even as well as odd harmonics can be seen as a bonus, but that's a question of taste. Odd harmonics never hurt the TubeScreamer, somehow.

[mrmet5]

In particular I was testing single and 2-and-1 asymmetrical clippings using MA150. I was expecting the single clipping to be drastically different from the 2-1 configuration, because, as I was assuming, one side is clipping at 0.95-1.2v while the other side is unclipped. I heard a little difference but not as much as I expected. The reason I asked was because I wanted to make sure I could use one diode as an asymmetrical clipping because I don't think I've ever seen a single diode clipping before (granted I'm fairly new to electronics). But now I know that simply it can be done. Thank you all for educating me!!

[Steben]

As a matter of fact, harmonic enhancers tend to clip with one diode and mix this with the dry signal.

[Steben]

For my part, much of the appeal of discrepant diode sets is really more the increase in output level one gets from it, by lifting the ceiling on one half cycle, and the slightly greater dynamic range (i.e., ability to get cleanish tones when picking softly, with dirtier tones when you pick hard), instead of the more dynamically compressed sound of fewer diodes or use of those with lower forward voltage.

+1 agree. This is an excellent point. The asymmetric diodes give you some clipping at lower levels, and then a bit more when you dig in. This is often exactly what we're after (though there are lots of potential ways to achieve this, clearly). The tendency towards some even as well as odd harmonics can be seen as a bonus, but that's a question of taste. Odd harmonics never hurt the TubeScreamer, somehow.

No but it is the dullest drive circuit I know.   

[Mark Hammer]

One way of achieving asymmetry is via use of a resistance in series with one of the diodes in a pair.  In fact I did this for a pedal some 20 years back, that I sold to one of Canada's finest blues guitarists.  It was simply a TS-9 clone with a little more bass, and a "warp" control (thanks for that, Jack) in the form of a 10k variable resistance in series with one out of the two feedback diodes.

In fact, many of the schematics for the Harmonic Percolator you see posted around use two diodes to ground for clipping, with a resistor in series with one of those diodes.

Asymmetry can be achieved in many ways.

[m4268588]

[jafo]

In particular I was testing single and 2-and-1 asymmetrical clippings using MA150. I was expecting the single clipping to be drastically different from the 2-1 configuration, because, as I was assuming, one side is clipping at 0.95-1.2v while the other side is unclipped. I heard a little difference but not as much as I expected. The reason I asked was because I wanted to make sure I could use one diode as an asymmetrical clipping because I don't think I've ever seen a single diode clipping before (granted I'm fairly new to electronics). But now I know that simply it can be done. Thank you all for educating me!!

That's really weird! The effect should not be subtle; the Bazz Fuss, for example, soft-clips one polarity via diode, and engaging it makes a huge difference.

Maybe your signal level is too low to be clipped? That would result in the effects you're noticing.

[Vivek]

Is there an audible difference between

Asymmetrical clipping due to different number of diodes in each limb

and

Asymmetrical clipping due to different value of compliance resistors in front of same number of diodes in each limb

[antonis]

Is there an audible difference between

Asymmetrical clipping due to different number of diodes in each limb

and

Asymmetrical clipping due to different value of compliance resistors in front of same number of diodes in each limb

From oscilloscope or physchoacoustics point of view..??

[Steben]

Is there an audible difference between

Asymmetrical clipping due to different number of diodes in each limb

and

Asymmetrical clipping due to different value of compliance resistors in front of same number of diodes in each limb

For classical music purists noise is noise

Seriously I'ld say intermodulation distortion is less present in soft and symmetrical clipping.

[Mark Hammer]

Jeez Louise, it's rock and roll!  Are ANY folks out there going to be feeding such a signal into a pristine amplifier with ridiculous amounts of headroom and NO propensity to add coloration?

[Steben]

Jeez Louise, it's rock and roll!  Are ANY folks out there going to be feeding such a signal into a pristine amplifier with ridiculous amounts of headroom and NO propensity to add coloration?

You know some  (especially youngsters) try to add "the" magic dirt box in front of a clean SS amp. 

[ElectricDruid]

Jeez Louise, it's rock and roll!  Are ANY folks out there going to be feeding such a signal into a pristine amplifier with ridiculous amounts of headroom and NO propensity to add coloration?

You know some  (especially youngsters) try to add "the" magic dirt box in front of a clean SS amp. 

Or, worse still, a 24-bit, 192KHz audio interface! That's a pretty unforgiving way to listen to what your pedal is putting out!