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VHD Pre Module 500 Series

Variable Harmonic Drive Preamp module for 500 format racks

SRP £429.00 + VAT

Delivery everything from ultra-clean to slightly warmed to heavily distorted recordings


The VHD Pre Module for the popular 500 format modular rack platform makes the uniquely versatile VHD based preamp technology from Duality, SSL's industry-leading large format studio console, available for studios of all sizes.


The VHD Pre is an immensely versatile recording and processing device. It can deliver ultra-clean SSL SuperAnalogueTM grade recordings but also features a switchable VHD mode. SSL's patented Variable Harmonic Drive (VHD) system uses a 100% analogue signal path to generate rich harmonic distortion. As you increase VHD input gain, the Variable Harmonic Drive process introduces either 2nd or 3rd harmonic distortion or a blend of the two to your source material. At lower gain settings it adds gentle valve-style warmth or a touch of transistor edge. As the gain is increased the more extreme the distortion becomes until at high gain settings it delivers fierce trashy transistoresque grunge. The VHD Pre gives the user ultimate versatility from a studio grade preamp. Whether it's ultra-clean traditional SSL, subtle warming or totally trashy transistor distortion, VHD will change your expectations of what a preamplifier should deliver.


The VHD section of the VHD Pre Module has three rotary controls: a Drive control selects 2nd harmonic or 3rd harmonic distortion or a continuously variable blend of the two. A +20/+75dB gain control sets input level. A -20/+20dB trim control adjusts the output level from the circuit to enable level matching with other devices, because by its nature the VHD circuit can significantly increase signal levels. The VHD Pre Module has a selection of other essential professional preamp features: a signal present LED, a switchable 15Hz to 500Hz LF Filter section, Hi-Z impedance switch for mic impedance matching, +48V phantom power, PAD to enable the VHD system to be used as a line-level processing device and a Phase Invert Switch.


  • Key Features:
  • Uniquely versatile recording and processing
  • Ultra clean SSL SuperAnalogue grade preamp
  • Switchable VHD system adds controllable 2nd or 3rd harmonic distortion
  • Switchable LF Filter (15Hz to 500Hz)
  • Hi-Z switch for high impedance microphone use
  • +48V Phantom Power with status LED
  • PAD for use with line level source material
  • Phase invert switch
VHD Input Module
Physical
Depth200 mm (including front panel knobs, excluding connectors
-275 mm (including front panel knobs and connectors)
Height171 mm
Width35 mm (front/rear panels)
-49 mm (overall width (front and rear panels are offset))
Weight260 g
Boxed Weight460 g
EQ Filters
HF (Low Pass)20kHz – 3kHz (–3dB point) - 12dB/Octave
LF (High Pass)15Hz – 350Hz (–3dB point) - 18dB/Octave
Performance Specification
Microphone Amplifier Performance
GainContinously variable from +20dB to +70dB - Independently switchable 20dB Pad available
Input ImpedanceContinously variable from ≅1k2Ω to ≅10kΩ
Output Headroom> +26dBu at onset of clipping
THD + Noise(-18dBu applied, +28dB gain) - < 0.2% (20Hz - 20kHz)
Frequency Response20Hz to 20kHz - +0.3dB
-50kHz - -3dB
-150kHz - –3dB
Equivalent Input Noise(input terminated with 150Ω) - < –126dB at maximum gain
Common Mode Rejection(-10dBu applied, +30dB gain) - > 75dB from 50Hz to 1kHz
Line Input Performance
GainContinously variable from -24dB to +24dB
Input Impedance10KΩ
THD + Noise(-24dBu applied, +0dB gain) - < 0.05% from 20Hz to 20kHz
Frequency Response20Hz to 20kHz - +0.1dB from 20Hz to 20kHz
Equivalent Input Noise(Input terminated with 150Ω) - -90dB