HA670N

Authentic Fairchild Tone

Captures the iconic Vari-Mu compression sound heard on countless hit records over the past 70 years.

Enhanced Modern Functionality

Delivers the legendary tone with 150% more control and features, perfectly tailored for today’s studios.

Transformer-Coupled Output Gain

Includes advanced output gain make-up using the HA-880 opamp for clean level adjustment without affecting tone.

6 Custom Attack and Release Settings

Improved timing controls offer more flexibility than the original unit, ideal for modern production needs.

Progressive DC Threshold

Provides smooth transitions from limiting to transparent compression with variable knee and ratio control.

Advanced Side-Chain Filtering

Built-in filters optimize performance for contemporary mixing and mastering tasks.

Independent Channel Bypass

Each channel has its own bypass for instant A/B comparison and workflow convenience.

Dual Mono or Stereo Operation

Supports both stereo linking and independent channel use, with MID/SIDE (LAT/VERT) processing capability.

NOS Tubes and Custom Transformers

Built with the same premium NOS tubes and six custom transformers as the original HERCHILD 670.

Compact Yet Powerful

All this functionality packed into a sleek 5U rack unit with a timeless design and solid build quality.

Affordable for All Studios

Offers flagship-grade performance at a fraction of the cost so it is designed for engineers who demand pro sound without breaking the bank.

General Specifications

Device Type: Dual-Channel Vari-Mu Tube Compressor

Format: 5U 19" Rackmount

Circuit Topology: True Vari-Mu based on Fairchild 670 architecture

Core Components: 4× NOS military-grade 6BA6 tubes, 6× custom-made transformers

Opamp: HA-880 transformer-coupled output stage

Construction: Hand-built in Madrid, Spain

Aesthetic: Vintage-inspired black front panel with dual VU meters

Compression Features

Channels: Dual Mono / Stereo / Mid-Side (LAT/VERT)

Compression Type: Tube-based Vari-Mu

Attack/Release Times: 6 stepped Time Constant settings

DC Threshold: Progressive, combines ratio and knee control

Slope Control: Continuously variable

Sidechain: Selectable high-pass filter (SC Filter) for each channel

AGC Link Modes: IND / LAT-VERT / LINK

Control Interface

Input Gain: Stepped, independent for left and right channels

AC Threshold: Stepped, independent for left and right

DC Threshold: Stepped, independent for left and right

Time Constant: 6-position stepped switch per channel

Output Gain: Stepped make-up gain per channel

Bypass: Independent hardware bypass per channel

VU Meters: Dual analog for input/output or gain reduction metering

Connectivity and Integration

Channel Modes: Dual Mono / Stereo / Mid-Side

Control Layout: Fully stepped knobs for recall accuracy

Modern Features: Independent bypass, sidechain filtering, stepped output gain, transformer-based opamp stage

Dimensions and Weight

Rack Units: 5U

Dimensions: Not explicitly listed, standard 5U rack width assumed

Weight: Not specified, but estimated heavy-duty due to transformers and tube build

Power and Performance

Tubes: 4× NOS 6BA6 (military-grade)

Noise: Designed for low-noise, high-headroom performance

Application Use: Tracking, Mixing, Mastering

Highlights

Faithful Fairchild 670 sonic recreation with added modern functionality

Sidechain filtering and mid-side processing support

Output gain stage with HA-880 transformer-coupled opamp

Affordable alternative to traditional Fairchild recreations

Ideal for modern studios seeking analog warmth without vintage limitations