Helix Amp Models

## Guitar Amp Models

* ÷13 JRT 9/15 Divided Duo
* Bogner Shiva German Mahadeva
* Bogner Überschall German Ubersonic
* Dr Z Route 66 Interstate Zed
* ENGL Fireball 100 ANGL Meteor
* Fender Bassman Tweed Blues (normal, bright channels)]]
* Fender Champ US Small Tweed
* Fender Deluxe Reverb US Deluxe (normal, vibrato channels)]]
* Fender Twin Reverb US Double (normal, vibrato channels)]]
* Hiwatt DR-103 Brill WhoWatt 100
* Gibson EH-185 Stone Age 185
* Marshall JCM-800 Brit 2204
* Marshall JTM-45 Brit J-45 (normal, bright channels)
* Marshall Super Lead 100 Brit Plexi (normal, bright, jumped channels)
* Matchless DC30 Matchstick (channels 1, 2, jumped) *(added in 1.06.0)*
* MESA/Boogie Dual Rectifier Cali Rectifire
* Orange OR80 Mandarin 80
* Park 75 Brit P-75 (normal, bright channels)
* Peavey 5150 PV Panama
* Roland JC-120 Jazz Chorus Jazz Rivet 120
* Silvertone 1484 Mail Order Twin
* Soldano SLO-100 Solo Lead (clean, crunch, overdrive channels)
* Supro S6616 Soup Pro
* Vox AC-15 Essex A-15
* Vox AC-30 with top boost Essex A-30
* Vox AC-30 A-30 Fawn (normal, bright channels)

* Line 6 Elektrik
* Line 6 Doom
* Line 6 Epic

## Bass Amp Models

* Ampeg B-15NF Portaflex Tuck n' Go
* Ampeg SVT SV Beast (normal, bright channels)
* Gallien-Krueger GK 800RB G Cougar 800
* MESA/Boogie Bass 400+ Cali 400 (channels 1, 2)
* MESA/Boogie M9 Carbine Cali Bass

## Amp Parameters

### 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 map 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.

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.

### *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 between distortion between power tube saturation and distortion from power tube cutoff. Proportion changes depending on the idling state of a power tube. 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 it's as if we can change the value of the cathode bias resistor.*

### *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 presents 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, 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 the 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.*