Amps

Quick Notes

  • Invented control starting point for neutral settings (setting to simulate the real stuff, without those invented parameters). But you can play with this values, it’s up to you (no limits):
    Presence for No Presence amps should be zero (all the way counterclockwise). Exception Jazz Rivet (P: 50%).
    Eq bonus controls to noon (50%) for No Mid, No Bass, No Treble amps.
    Master parameter for no master amps to 100%.
  • Real amps with Volume means Gain in Helix. Volume in Helix is like a mixer to compensate final modeled output level (obviusly it doesn’t exist in any of the real amps).
  • To attenuate “Crossover Distortion“, the best parameter in Helix is “Bias“, increase it from 6 to 8 as general rule just in case you need to mitigate it.
  • The default Line 6 amp settings parameters for Helix, when you open a modeled amp, are also a good starting point, normally they are close or exactly in concordance with this. Tip : double click in the parameter to come back to the default one.
  • For Pre Amps models in Helix, some power amp related parameters (i.e presence in general ; or cut tone with Vox amp )are not present, but they modeled also Master and Sag with PreAmps.
  • All amps are modeled on the Input 1 (High). If you want simulate Input 2 (low), then use a gain block to take 6dB off the signal, and change the input impedance to something lower; somewhere between 68k and 150k.

Common Amp Settings

Parameter Description
Master Adjusts the amount of power amp distortion: 0% clean 50% normal, 100% driven. Note that 50% may not be normal as the amps may have been modeled with the Master set too high. Consider using lower values, or the minimum distortion required to fit the song.

This parameter is highly interactive with all other power amp parameters—the lower the Master is set, the less effect the other controls will have.

Low Master and high Drive gives smother preamp distortion while high Master lower Drive gives more power amp, symmetric and more aggressive distortion.

Sag Controls power amp sag or compression: 0% tight, 50% normal, 100% more touch for dynamic sustain.

Lower Sag values offer a “tighter” responsiveness for metal and djent playing; higher values provide more touch dynamics & sustain for blues and classic rock riffs. High Bias (closer to class A) reduces the effect of the Sag control. Sag doesn’t exist in class A amplifiers since the average plate current doesn’t change.

Sag is caused by the amplifiers power supply being unable to meet the demand when the amp is pushed hard with high Master. When the power sags, the amp output drops and then recovers, creating a unique compression effect with some additional, but temporary distortion when you pick hard. Unlike compressors before the amp, sag compression occurs even when the amp is already very distorted.

Large sag gives more compression, better sustain, and can accentuate pick attack. But the amp will appear somewhat less responsive especially at the low end and can get muddy.

Hum Controls how much heater hum interacts with your tone. Tube amplifiers generally used low voltage AC in the tube heaters, and sometimes this could add some hum into the signal.

At higher settings, things get freaky. Higher levels cause some intermodulation distortion as the heater hum mixes with the signal. Generally left at 0 unless you are looking for a specific effect.

Ripple Controls how much AC ripple in the power supply interacts with your tone. The power supply of a tube amp is filtered with large capacitors. If the amp is driven hard, these capacitors can’t provide sufficient filtering and some AC ripple is introduced into the signal. This is similar to hum but is on the plate of the tube instead of the heater and has a different shape.

This article The Strange Effects of AC Ripple on a Class AB Power Amp indicates AC power supply ripple can have more impact on guitar amp tone than one might expect. Some power supply ripple will add overtones caused by intermodulation distortion to the the sound that might be pleasant. Too much will be audible, but backing down from the point at which the ripple creates noticeable unpleasant artifacts might actually contribute to nice tone.

At higher settings, things get freaky. Also generally left at 0 unless you are looking for a specific effect.

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.

Further tone control information

Originally posted by Ben Adrian here.

I’ll do my best to answer this while also playing it safe and not giving away anything that might get me a stern talking-to.

Bias on cathode biased amps.

Many people have an association that cathode biased = class A. This is usually not true. However, most cathode biased amps are running the tubes hotter than most fixed bias amps. The Bias control affects the balance of distortion between saturation and cutoff in the power tubes. Proportion changes depending on the idling state of a power tube; if it’s idling hot, then there will be more saturation and less cutoff, and if it’s cold there will be more cutoff and less saturation. The bias control affects where the idling state of the tube is “located”; if it’s hot or cold. Another way of putting it might be that we can virtually change the value of the cathode bias resistor in a cathode bias amp.

All these extra knobs.

If an amp has a small number of knobs, then we will invent the knobs in a way that makes the most sense to us. First, let me say that the Channel Volume (ChVol) knob is ALWAYS a flat response, post amp model level control. This is like a fader on a console. It’s in the amp model, but it’s not tied to the tonality of the amp model. It’s how I level different presets so that they play well together.

The Drive knob corresponds with the Drive or Gain knob on master volume amps. With amps that don’t have a master volume, it corresponds with the Volume knob. So, on the Deluxe model that you reference, the Drive knob is the Volume control on the front panel.

The Master Volume knobs in Helix map to the Master volume knobs on amps with Master Volume controls. If the amp does not have a master volume control, then we add one similar to where an amp tech might add one to an amp if the amp was having one installed. In the case of the Deluxe, this is between the preamp and the power amp. This can be thought of as a passive volume reduction. Master @ 10 is like it’s not in the circuit. As it is turned down, the level from the preamp into the power amp is reduced.

Tone controls. We try to make them fit the character of the amp. In the Deluxe Reverb, the tone controls are exactly like that or a twin reverb except the 10k linear midrange knob is replaced with a fixed 6.8k resistor. If you want to match the model to the actual amp, set the model between 6.1 and 6.8 (values drift in the real amps. My idea, though, was to make the midrange knob on the deluxe behave like the midrange knob on other black-face fender circuits that have a midrange control.

In other amps, tone controls gets invented on a per-amp basis. In the tweed champ, the bass and treble are after the amp modeling, but the midrange control is between the two preamp gain stages. The midrange knob can become a cool drive feature. In some amps, the invented controls come between the preamp and the power amp. In short, we tried to make it sound good, and we tried to respect what is happening in similar classic amp circuits.

Cheers!

Thank you amsdenj of the Helix community for providing further information about the Common Amp Settings and duncann for providing the link to Ben Adrian’s information regarding tone controls.