Explainer
Stack vs BIAS FX (and BIAS X): Guitar Amp Plugins Compared (2026)
Updated 2 min read
BIAS FX 2 has been replaced by BIAS X, Positive Grid's current guitar platform: 33 amps, 63 effects and 25 cabs, dual signal chains, AI tone tools and a standalone app, for $149 list. Stack is a focused amp sim with four amps (Clean, Crunch, Lead, Bass), four cabinets plus DI, three pedals and a room, built to sound good fast, for €49. Pick BIAS X for a huge rig and AI-assisted tone matching; pick Stack for quick, amp-like tones in your DAW with fewer choices.
Stack vs BIAS X at a glance
Price (list)
- Stack
- €49 once
- Positive Grid BIAS X
- $149, perpetual, up to 5 devices
Formats
- Stack
- VST3, AU, AAX
- Positive Grid BIAS X
- Standalone; AU, VST3, AAX (Mac); VST3, AAX (Windows)
Amps
- Stack
- 4: Clean, Crunch, Lead, Bass
- Positive Grid BIAS X
- 33
Cabinets
- Stack
- 4 (1×12, 2×12, 4×12, bass 8×10) plus DI
- Positive Grid BIAS X
- 25
Effects
- Stack
- Gate, drive, compressor, chorus, room
- Positive Grid BIAS X
- 63
Signal chains
- Stack
- One
- Positive Grid BIAS X
- Dual
AI tone tools
- Stack
- No
- Positive Grid BIAS X
- Text-to-Tone, Music-to-Tone
Internet needed
- Stack
- No, license key works offline
- Positive Grid BIAS X
- For activation and the AI features
What BIAS X does well
BIAS X is a full guitar rig: 33 amps, 63 effects and 25 cabinets, with dual signal chains for blending rigs and support for Neural Amp Modeler captures. Its AI tools build a tone from a text description (Text-to-Tone) or from a piece of music (Music-to-Tone), and it runs as a standalone app for practice as well as a plugin. It suits players who want every pedal and amp option, tone matching and a practice app in one purchase.
What Stack does well
Stack keeps the rig small and makes each part behave like hardware. Its Bass, Mid and Treble controls are solved from each amp's passive tone-stack circuit every time you turn a knob, so they interact the way they do on a real amp, and the gain stages are 4× oversampled with power-amp sag. Choose a cabinet and slide the mic from bright centre to warm edge, add drive, compressor or chorus in front, and blend in the dry DI with Mix. 48 level-matched presets cover clean, crunch, blues, indie, funk, metal, bass and ambient tones.
Where BIAS X is stronger
- Scale: many times more amps, cabs and effects.
- AI tone matching from text or a song.
- Standalone app for practice without a DAW, and dual signal chains.
- NAM support for loading Neural Amp Modeler captures.
Where Stack is stronger
- Fewer decisions: four amps and four cabs that each sound right fast.
- Circuit-solved tone controls that respond like the real amp.
- Works offline with no internet activation.
- Price: €49 once, and every preset plays in your browser on DI guitar and bass before you buy.
Which should you choose?
- You want a huge rig, AI tone matching or a standalone practice app: BIAS X.
- You own BIAS FX 2: BIAS X is its successor, with an upgrade price, but Positive Grid says FX 2 presets and expansions don't carry over.
- You want great amp tones in your DAW quickly, for guitar and bass: Stack.
Getting set up? Read how to record guitar into a computer, and see our guitar plugins page.
Try Stack in your browser
FAQ
Is BIAS FX 2 still available?
No. As of November 2026, Positive Grid's BIAS FX 2 page says the product is no longer for sale and points to BIAS X, its successor. Positive Grid notes that BIAS FX 2 presets and expansions don't carry over to BIAS X.
How much is BIAS X?
As of November 2026, Positive Grid lists BIAS X at $149 as a perpetual license for up to five devices, with frequent sales. It runs standalone and as a plugin (AU, VST3 and AAX on Mac; VST3 and AAX on Windows).
What is an amp sim?
Software that models a guitar amplifier, speaker cabinet and microphone, so you can plug straight into an audio interface and record without a real amp. Stack has four amps, four cabinets plus a DI option, pedals and a room.
Are there free guitar amp plugins?
Yes, several, and many DAWs include an amp sim too. Our [best guitar amp plugins](/learn/best-guitar-amp-plugins) roundup covers free and paid picks.