APX 351
The Holy Grail Tube Pre-Amp
Single-channel tube preamp emulation with Class-A gain stage, neural-modeled triode saturation, Soft/Hard modes, Ultra-X mode, Dry Mix, HPF/LPF & Auto-Gain
VST3 · AU · AAX | Windows & macOS
★ Full version trial for the first 15 Days
* License Authorization needs an internet connection
The Sound of Analog
Single-Channel Tube Preamp
The APX 351 is a single-channel tube preamp emulation with a Class-A gain stage and transformer-coupled input/output. Featuring neural-modeled triode saturation for authentic harmonic coloration, it delivers the warm, musical character that defined legendary recordings.
- Single-channel tube preamp emulation
- Class-A gain stage with transformer-coupled input/output
- Neural-modeled triode saturation for authentic harmonic coloration
- Subtle tape-era frequency roll-off and midrange lift
- Natural soft clipping at high input levels
- High-impedance input suited for instruments, vocals, or mix busses
Soft & Hard Modes
Choose between two distinct saturation models captured from the original hardware. Soft mode delivers gentle, musical warmth perfect for vocals and acoustic sources. Hard mode pushes into driven saturation territory, ideal for adding tube-style grit to drums, bass, and aggressive sources.
- Soft mode for light, musical saturation
- Hard mode for driven, aggressive character
- Both models captured from real hardware
- Smooth transition from warmth to grit
- Works beautifully on every source
Ultra-X Mode
Very high sample rate models for artifact-free processing
192kHz Ultra-High Resolution
Ultra-X mode activates very high sample rate models which minimizes aliasing artifacts at extreme settings. This plugin features a high sample rate training model set for virtually removing artifacts such as aliasing from the sound and offering a higher frequency response.
- NM2 Neural Technology
- 192kHz Ultra-High Resolution processing
- Minimized aliasing at extreme settings
- Higher frequency response
- Virtually artifact-free sound
Audio & Video Demos
See and hear the APX 351 in action
Overview
Demo
Audio Samples
Works On Everything
Vocals, guitars, drums, synths, mix bus — anywhere you need vintage tube warmth
Vocals & Guitars
Add warmth and vintage character to vocals, guitars, and synths with authentic tube saturation.
Drums & Bass
Drive harder for tube-style saturation and grit on drums or bass. Hard mode delivers serious punch.
Synths & Samples
Enhance sampled instruments or sterile digital sources with analog flavor and harmonic richness.
Mix Bus Glue
Insert on the mix bus for cohesive, retro-inspired depth and tone. Subtle harmonic thickening.
Transient Smoothing
Smooth transient peaks without traditional compression. Natural soft clipping at high input levels.
Harmonic Thickening
Glue mix elements together with subtle harmonic thickening and vintage tube character.
User Testimonials
Congrats to the ToneEmpire Team! This one sounds amazing. Sweet what it does to the transients and the stereo image. I tried it on the drum bus and the mix bus = instant Hi-Fi sound. Love it!
Sounds nice, the gain also is very close good work there. When gain match is just volume up and volume down the same amount it never really works, the scaling you have here is just perfect. Softube has a match system that requires u click a button and it takes second and matches the gain. but this is that much faster :-)
Ok now I have demoed this preamp on an electric guitar and I actually like it! A lot more presence and 3D.
Features & Controls
Control the input gain / drive to the valve processing
This is the control for output attenuation after the valve processing.
Automatic gain compensation to maintain consistent levels as you adjust the drive control.
Choose from soft and hard models captured for light or driven model of saturation.
Use this control to further adjust the input signal gain before processing.
Use this control to trim the final output of the processing after the filters and the dry mix.
Add the original unprocessed signal to the mix as parallel processing.
This filter is applied post processing to control some of the upper harmonics if needed by the user. The range is 2kHz to 20kHz.
This filter is applied pre processing to control some of the low end if needed by the user. The range is 20Hz to 2kHz.
Ultra-X mode for very high sample rate models which minimizes aliasing artifacts at extreme settings.
Specifications
Plugin Formats
macOS: VST3 / AU / AAX (64-bit)
Windows: VST3 / AAX (64-bit)
Windows 10 or later
macOS Mojave or later
Apple Silicon / Intel / AMD Native
System Requirements
Intel i3 / AMD Ryzen or equivalent
2 GB RAM minimum
300 MB HD space
VST3, AU, or AAX 64-bit host
Internet connection for license activation
Installation
macOS: Download the apx351.pkg file, double-click and follow instructions
Windows: Download apx351.exe and follow instructions
Online license registration system
Compatible with all major DAWs
NM2 Neural Engine with Ultra-X mode