POD HD Amplifier Extras—Using the Sag, Bias and Bias Excursion Settings

POD HD Amplifier Extras—Using the Sag, Bias and Bias Excursion Settings

It’s probably accurate to say that most of us haven’t checked out the extra features that were added to the power amp section of POD HD some time ago. Some people I talk to assume that they were parameters added to please a small subset of tweaky gear dudes, and don’t really do anything of value. Other folks don’t know that they exist, or what to do with them.

This article deals specifically with three of these deep-editing parameters, and will hopefully demonstrate why you should play around with them a bit: Sag, Bias and Bias Excursion.

There is a wealth of information online regarding the technical background of these three terms, and instead of spending valuable space here I’ll just post this link from our Community Forum for you to check out before continuing, if you wish:


As you can see from the link above (and some of the links contained in the thread, if you really have a ton of available reading time), there is a bunch of technological stuff to get your head around, if you really want to understand how each of these parameters function. It requires a basic knowledge of tubes/valves and the electrical voltages and currents that flow in and out of them.

However, if you just want to know what they feel like and how they can help you in your quest for tone, that’s an easier thing to accomplish!

My goal with this article is to get you to experience the way that these parameters can change the way the amp feels to you—with the guitar in your hands. Much like the EQ CUT knob on a vintage Vox® AC30®, if you know what it really does when you turn the knob, you don’t really have to know how it does it. Even though there are video examples in this article, you really should set aside some time for trying this out yourself, as it will pay dividends later in the kind of control you’ll have over your tone.

So, let’s make a simple patch. We’re assuming that we’re running the POD HD direct into a pair of studio monitors or headphones, that it’s set to “Studio/Direct” mode, and we’re listening in stereo.

Navigate to a default patch somewhere in your POD HD—probably in one of the User banks that you’ve never used—and load it.

Create an amp in the amp block. To closer match what you’ll hear me do in a moment, choose the Plexi Lead 100 Bright amp, and leave all the cab and mic parameters at their default, as I did. You can see where the amp knobs are placed in the screenshot below.

Now, with your guitar plugged in and making noise, move the cursor to the amp block, and double-tap the ENTER button to see the deep parameters for the amp. Hit the right arrow on the navigation button twice to get to Page 2. You’ll see this:

[caption id="" align="alignnone" width="347" caption="Default Sag Settings"]Sag 50[/caption]

Before we go any further, let’s check out an example of the baseline sound. For these clips, the JTV-69 guitar went straight to a POD HD Pro, and from there out the XLR outputs to a pair of mic preamps, and then directly into Pro Tools HDX. There is no processing or EQ in Pro Tools on any of the following examples. All of the snippets are the Plexi Lead 100 Bright channel, using the magnetic pickups on my JTV-69.

All parameters at default:


Let’s start with the Sag parameter. You will undoubtedly associate your own word with what it does, but I think of it as “spongy” or “gooey.” It has some aspects to what it does that show up as frequency-dependent compression, and others that affect pick sensitivity. Higher values exhibit more sponginess when you play them, and produce more compression, grit and “glue” in the sound. Lower values really stiffen up the feel of the amp.

This clip raises the Sag level to 100:


You can see that there is now a lot more “goo” and crunch going on in the sound (maybe even too much). The pulled E-chord is more glued together than the same chord in the previous example, and the high plucked notes don’t poke out as much.

Let’s move to the next page of parameters. Before we move on, lower the Sag value back to 50, and hit the right arrow on the navigation button again to get to the Bias and Bias Excursion values on page 3. If you’re playing along, noodle a bit to remind yourself of what the amp feels like back at the default.

Bias current sets the operation “idle” for the tubes, and it has its own effect on the response of the amp. The default Bias setting is 50—if you’re not playing along at the moment, you may want to play the first clip again to remind yourself of the amp’s response.

The following snippet has the Bias turned down to 41. You can tell that the tone is a bit different—perhaps more glassy on the top end, and the high plucked notes get more glued together again, but they’re not quite as distinct as they still were when we cranked the Sag.


If we turn the Bias down to 0 and play the same things, the change is really apparent: the E chord is still glued together, but the high notes and string noise really stick out. The feel of the amp is much stiffer, and it’s a little harder to play for me as a hybrid picker, because all of the notes don’t get compressed together as much. It’s a great way to punch up a metal tone though.


So you can see that just these two controls—Sag and Bias—can make a world of difference in how the amp feels when used together.

Okay then, let’s put the Bias back to 50, and move to the Bias Excursion knob. In a very general sense, this parameter determines the return speed of the Bias correction to the tube. It also makes a huge difference. Play a bit again, noting how it feels at default.

Now turn the Bias Excursion up to 100 and play the same stuff. It’s almost as if the strings somehow have gotten a bit more metal in them all of the sudden—and the high notes are smoother again.


Turn the Bias Excursion to 0, and repeat. It feels a bit similar to the way it felt when the Bias was turned down to 0, but the strings make more noise, and the high notes are still glued together and don’t poke out as much.


Finally, here is the same sort of playing passages with a custom setting of all three parameters:


These videos will give you some idea of the changes possible using these three controls, but you really have to play them yourself to get the full effect. Changing the parameters makes the amp feel different, which in turn makes me play differently because as the amp gets spongier I have a tendency to hit the guitar harder. You can watch my right hand to get an idea of how hard I’m playing in each example, but it’s far easier to tell when you’re playing the guitar yourself.

The point to all of this is that those three knobs—Sag, Bias and Bias Excursion—are now almost as important to me as the EQ knobs on the front of the amp. I always keep them in mind when I’m dialing in tones using the full models, and the Sag in particular is a knob that I always tweak any time I change an amp model… it’s just become part of my creation process.

I should also mention that one of the cool things about having tweaking power this deep is that you can help out your live sounds too. Just take the time to set up all of your tones in your home studio, and then take them out and use them on your next gig by running direct to the PA. Even better, take your POD HD to a store that has a Line 6 StageSource L2 speaker, and check out what 800 watts RMS sounds like on your guitar sounds—I’ve been doing some pop gigging lately with this scenario (a pair of L2’s actually), and it’s pretty incredible.

The website is here:


Hope this helps! Until next time,