Alpha VHD-Pre

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Product Description

The Four-Channel Mic Pre/Processor with attitude.

Change your expectations of what a preamplifier should deliver.

The Alpha VHD-Pre offers four of SSL’s widely acclaimed VHD Pre circuits in compact 1U format. First featured on our flagship Duality console and now the go to circuit for leading engineers worldwide, the VHD Pre is a patented SSL preamp design that can deliver ultra-clean SSL grade recordings but also features a patented ‘Variable Harmonic Drive’ circuit which can be switched into the signal path. The Variable Harmonic Drive circuit uses a 100% analogue signal path to generate rich harmonic distortion. As you increase the input gain, the Variable Harmonic Drive circuit 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. VHD pre’s give the user ultimate versatility from a studio grade preamp. Whether it’s ultra-clean traditional SSL, subtle warming or totally trashy transistor distortion. VHD delivers a uniquely versatile pallette of rich analogue character that can be applied as a mic pre, instrument DI or line level processing device.

Each Pre is a simple analogue device with XLR in/out on the back, an instrument level 1/4″ jack on the front panel. Each circuit has a Hi Z switch to accommodate mic, line and instrument level signals, a PAD switch to facilitate use as a line level processing device and 48v phantom power switch. There are three rotary controls: Input Level, VHD and Output Level.

Key Features

  1. Ultra-clean SSL preamp with 75dB of gain
  2. 48V phantom power
  3. 20dB Pad switches that illuminate to indicate overload
  4. Hi Z switches to accommodate mic, line and instrument level signals
  5. Four independent Variable Harmonic Drive systems
  6. Front panel 1/4″ jack instrument/line level inputs with passive DI type impedance detection and level matching
  7. Individual input, output and VHD controls for each section
  8. Rear panel XLR mic/line inputs and XLR outputs
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Additional Information


Power Supply IEC320 3-pin connector, 100 – 240 Vac, 50 – 60 Hz
Analogue I/O
Microphone Balanced, 3-pin XLR-F, Zin = 1kΩ (10kΩ for Hi Z)
Instrument Un-balanced, ¼" Mono Jack, Zin = 1MΩ
Output Balanced, 3-pin XLR-M, Zo = 40Ω
Power 5-pin 180° DIN connector, +5Vdc, ±15Vdc


Physical *
Depth 230mm / 9" casing only
Height 44.5mm / 1.75" (1 RU)
Width 438mm / 17.25" casing only
482mm / 19" inc’ rack ears
Weight 2.6kg / 6 pounds
Power < 20 Watts
Boxed size 320mm x 550mm x 80mm
12.75" x 21.75" x 3.25"
Boxed weight 3.5kg / 8 pounds

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