Implemented A way to cut down blocking distortion?

jon

jon

Fractal Fanatic
A recent post got me thinking.....

Now I'm no expert but I realized that blocking distortion is not something I like. Turns out most others don't either, they just don't know what it is to call it out by name - but it's generally quite undesirable, and has caused quite a few 'is my axe fx/this FW broken?!' posts too.

Amps are obviously complex beasts and each is different, so maybe this may be more a request for a 'Cliff's notes' on the subject, as the solution for each amp may likely be different, or maybe....not? There is no better expert on the subject than Cliff himself, so is there a way to 'generally' reduce blocking distortion?

I know there are quite a few tricks - maybe adjust the Phase Inverter Bias Excursion? Maybe user selectable grid stopper resistors? Adjustable coupling capacitor values? The option for dropping in virtual clipper diodes? Reducing negative feedback? Or just a good Cliff's notes on the subject so we can all understand how to dial it out? Or maybe for the odd one of us that actually LIKES that awful sound, a way to dial it in?

Again, I'm nowhere near as versed as some of the guys here or Cliff himself, but I'm thinking there must be some way to reduce some of these undesirable artifacts, which will make a LOT more amps in the Axe iii more pleasant and usable favorites. There are some ideal (and VERY GOOD) FAS models, but short of having ideal FAS models for everything (not opposed to this either!), there must be some way to generally reduce this.

So I'm throwing this out as a challenge for those more knowledgeable about the subject to offer suggestions on how this might be achieved - maybe we might stumble upon something cool....maybe this might spark that FW 13, or worst case maybe we just all understand this whole thing better..........just wanna get some gears turning here 😎
 
jon said:
A recent post got me thinking.....

Now I'm no expert but I realized that blocking distortion is not something I like. Turns out most others don't either, they just don't know what it is to call it out by name - but it's generally quite undesirable, and has caused quite a few 'is my axe fx/this FW broken?!' posts too.

Amps are obviously complex beasts and each is different, so maybe this may be more a request for a 'Cliff's notes' on the subject, as the solution for each amp may likely be different, or maybe....not? There is no better expert on the subject than Cliff himself, so is there a way to 'generally' reduce blocking distortion?

I know there are quite a few tricks - maybe adjust the Phase Inverter Bias Excursion? Maybe user selectable grid stopper resistors? Adjustable coupling capacitor values? The option for dropping in virtual clipper diodes? Reducing negative feedback? Or just a good Cliff's notes on the subject so we can all understand how to dial it out? Or maybe for the odd one of us that actually LIKES that awful sound, a way to dial it in?

Again, I'm nowhere near as versed as some of the guys here or Cliff himself, but I'm thinking there must be some way to reduce some of these undesirable artifacts, which will make a LOT more amps in the Axe iii more pleasant and usable favorites. There are some ideal (and VERY GOOD) FAS models, but short of having ideal FAS models for everything (not opposed to this either!), there must be some way to generally reduce this.

So I'm throwing this out as a challenge for those more knowledgeable about the subject to offer suggestions on how this might be achieved - maybe we might stumble upon something cool....maybe this might spark that FW 13, or worst case maybe we just all understand this whole thing better..........just wanna get some gears turning here 😎
Click to expand...

Per my response in the thread that was the inspiration for your post, I was able to seriously mitigate the effect by simply using the bridge vs. neck pickup.
 
Per the manual:

Bias Excursion – The higher the value, the more the bias shifts when the virtual power tubes are overdriven. Bias excursion pushes a power amp from Class-AB operation towards Class-B operation, which can result in crossover distortion. A little goes a long way, but too much can lead to what is referred to as “blocking distortion” which can make an amp sound unpleasant.
 
Yeah that was indeed my first guess above 🤣

I did indeed read it in the manual - if that’s all there is to is well I'm a happy camper, and case closed 😎
 
Mark Al said:
I just retried reduce the Bias Excursion down to zero, it made zero difference for the distortion referred to here:
https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-10.162959/post-1953601

So I assume the dissonant distortion discussed in the thread above is NOT block distortions.
Click to expand...
You’re hearing intermodulation distortion. That happens anytime you’re playing two or more notes with distortion.

In the example, you’re playing an E and a G. That’s going to produce some dissonant intermodulation products. A root and a fifth will produce more pleasant intermodulation (that’s why power chords work so well with distortion), so try the low E and the B on the seventh fret of the high E string. It won’t sound so nasty.
 
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