Cleaning Up Your Amps Using the Bias Parameter

Using the Bias Parameter to Get Your Amps Sparkling Clean

Have you ever wanted to create a sparkling clean amp tone with your Helix but didn’t want to resort to using the JC 120 amp model? It seems like on most Helix amp models, no matter how low the gain is set, there’s still a trace amount of distortion coming through your signal (especially if you have the master volume cranked). In today’s Helix Quick Tip you’ll see how it’s possible to get a crystal clean tone with any amp in the Line 6 Helix.

Because I’d like to keep this post as a quick tip (and also because my knowledge of amplifiers is fairly shallow), I’m going to avoid the technical details of Class A and Class AB amplifiers. For information on amplifier class specifications see the links at the bottom of this post.

IT’S ALL ABOUT THAT BIAS!

For the longest time, whenever I set out to create a new patch, I would always avoid the Bias parameter. The majority of the default amp settings on the Helix have the Bias set to 5.0. So I figured that’s where they should stay. Then one day, trying to force myself out of the box, I started messing with the Bias and discovered the effect it had on the overall tone.

The solution for cleaning up your amp tone is quite simple. Just increase the Bias. I’ve found my favorite settings for a clean tone will have the Bias set anywhere between 7.0 - 8.5.

According a post discussing the various Helix Amp Parameters on the Line 6 support forum, the Bias and Bias X parameters have the following effect on your tone:

BIAS

Changes the Bias of the power tubes. Lower values achieve a "colder" Class AB biasing. At maximum, the amp is operating in Class A.

Higher or “hot" bias will increase the warmth, reduce headroom, distort earlier or at a lower Master setting, and (in a tube amp) decrease the tube life. Lower or “cold" bias will make the sound less sweet, but will tighten it up and make it more dynamic.

BIAS X

Determines how the power amp tubes' voicing reacts when pushed hard, controlling how much the bias changes when the amp is driven hard. Bias X is a bit like Sag, except it controls change in a tube’s operating point due to change in the tube bias when the amp is driven hard.

Set low for a tighter feel. Set high for more tube compression. This parameter is highly reactive with the Drive and Master settings.

So there you have it. Now go start messing with your Bias settings to get your tone just right!

For more info on Class A and Class AB amps check out these articles:

https://reverb.com/news/what-is-a-class-a-amp-anyway-the-truth-behind-myths-and-misconceptions

https://mesaboogie.zendesk.com/hc/en-us/articles/225099807-What-is-Class-A-and-how-does-it-differ-from-Class-AB-


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