Solid State Logic VHD User Guide

VHD+ Pre Amplier Module

for 500 Series Racks

User Guide

-1-

Safety and Installation Considerations

This page contains denitions, warnings, and practical information to ensure a safe

working environment. Please take time to read this page before installing or using this

apparatus.

General Safety

• Read these instructions.

• Keep these instructions.

• Heed all warnings.

• Follow all instructions.

• Do not use this apparatus near water.

• Do not expose this apparatus to rain or moisture.

• Clean only with dry cloth.

• Do not block any ventilation openings.

• Install in accordance with the rack manufacturer’s instructions.

• There are no user-adjustments, or user-servicable items, on this apparatus.

• Adjustments or alterations to this apparatus may affect the performance such

that safety and/or international compliance standards may no longer be met.

• This apparatus is not to be used in safety critical applications

Caution

• This apparatus should not be used outside of the scope of API 500 series

compatible racks.

• Do not operate this apparatus with any covers removed.

• To reduce the risk of electric shock, do not perform any servicing other than that

contained in these Installation Instructions unless you are qualied to do so. Refer

all servicing to qualied service personnel.

Installation

• Ensure power is removed from the rack before tting or removing this apparatus to

or from the rack.

• Use the panel xing screws supplied with the rack to secure this apparatus into the

rack.

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Standards Compliance

This apparatus is designed to be installed and used in API
500 series compatible racks which are CE marked. The CE
mark on a rack is indicative that the manufacturer conrms
that it meets both EMC and the Low Voltage Directive
(2006/95/EC).

Instructions for Disposal of WEEE by Users in the

European Union

The symbol shown here is on the product or on its
packaging, which indicates that this product must not
be disposed of with other waste. Instead, it is the user’s

responsibility to dispose of their waste equipment by
handing it over to a designated collection point for recycling of
waste electrical and electronic equipment. The separate collection
and recycling of your waste equipment at the time of disposal will
help to conserve natural resources and ensure that it is recycled
in a manner that protects human health and the environment.
For more information about where you can drop off your waste
equipment for recycling, please contact your local city ofce, your
household waste disposal service or where you purchased the
product.

Limited Warranty

Please refer any warranty claim to the supplier of this equipment in
the rst instance. Full warranty information for equipment supplied
directly by Solid State Logic can be found on our website:

www.solidstatelogic.com

-3-

Introduction

Congratulations on your purchase of this API 500 format compatible
SSL VHD+™ Pre Module.

This module has been specically designed to operate in a 500 for­mat rack such as the API lunchbox® or equivalent. In common with
many such modules, the nominal input/output level is +4 dBu.

The VHD+ Pre is an immensely versatile recording and processing
device. It can deliver ultra clean SSL SuperAnalogue™ 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
erce trashy transistoresque grunge.

Operation

Please refer to the illustration opposite.

Signal LED

The signal LED is a tri-colour LED that indicates level according to
the following table.

LED colour +24dB Scale* +18dB Scale*

Green -24dBu -24dBu

Yellow +4dBu 0dBu

Red +21 dBu +16dBu

* The LED scale is selected from a jumper on the module PCB.

1

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Gain Controls

The red pot provides up to +75 dB of gain,
whilst the black pot provides a variable
mix of 2nd to 3rd order harmonics (once
the VHD-IN switch is engaged).

The grey pot provides +/- 20dB of trim.
Use this to control the output when driving
the VHD preamplier circuit.

2

3

1

3

2

High Pass Filter

The High Pass Filter section is a
switchable 18dB/Octave variable lter.
See the block diagram for the position in
the circuit.

Line In/DI Jack Socket

The front panel 1/4” Tip/Ring/Sleeve
(TRS) Jack Socket provides a convenient
way to connect instruments when the
module is tted in a rack.

This balanced input overrides the rear XLR and has a 10KΩ input
impedance and features a -10dB level pad to allow for typically
louder balanced line level signals. The Jack input can also be used
with unbalanced (TS) cables. The input level and impedance are
switched to 0dB and 1MΩ respectively (for very high impedance
sources such as guitar pick-ups) with selection of the HI-Z switch.

4

4

5

5

6

Input Impedances

The rear XLR and front Jack inputs have different impedances
available by using the Hi-Z switch and allow for a wide variety of
sources. The XLR input impedance changes from 1.2 KΩ to 10KΩ
and the front panel Jack changes from 10KΩ to 1MΩ.

-5-

SIGNAL

HPF IN

REAR

XLRM

PAD

FRONT

15-500Hz

+dB

-20 to +20dB

Ø

+dB

+20 to +75dB

-20dB

JACK

1M

HI-Z

1.2K
10K

+48V

10K

-10dB

FRONT

TRS

JACK

HPF

TRIM

GAIN

48V

Block Diagram

REAR

XLRF

-6-

Switch Functions

48v

Applies phantom power to the rear XLR input, a tell tale red
LED indicates phantom power is active.

PAD

Applies 20 dB of attenuation before the signal enters the
preamplier.

HI-Z

Switches the XLR Mic preamplier impedance from 1.2 KΩ
to 10KΩ or the front panel Jack from 10KΩ to 1MΩ

Ø

Polarity switch inverts the polarity of the signal by 180°.

6

Using the preamplier

When the VHD button is not engaged, the preamplier has been
designed to give a transparent sound, great for sources such as
acoustic guitars, vocals and strings.

When the VHD button is pressed, the preamplier can be driven to
give a wide-range of overdriven sounds, ranging from subtle to...
well, not so subtle! Drums and electronic instruments can often
benet from VHD colouration.

The best way to drive the VHD preamplier is to increase the input
gain (red pot) whilst using the Line Trim pot to reduce the overall
level and not clip the channel output. Remember, it’s the input to
the preamplier that likes being driven. From this point, adjust the
harmonics to ne-tune the desired sound.

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Visit SSL at:

www.solidstatelogic.com

© Solid State Logic

All rights reserved under International and Pan-American Copyright Conventions

SSL® and Solid State Logic® are ® registered trademarks of Solid State Logic.

SuperAnalogue™ and VHD+™ are trademarks of Solid State Logic.

All other product names and trademarks are the property of their respective owners and

are hereby acknowledged.

No part of this publication may be reproduced in any form or by any means, whether

mechanical or electronic, without the written permission of Solid State Logic, Oxford, OX5

1RU, England.

As research and development is a continual process, Solid State Logic reserves the right

to change the features and specications described herein without notice or obligation.

Solid State Logic cannot be held responsible for any loss or damage arising directly or

indirectly from any error or omission in this manual.

PLEASE READ ALL INSTRUCTIONS, PAY SPECIAL HEED TO SAFETY WARNINGS.

E&OE

July 2020

Revision History

Revision V2.0, June 2020 - Revised Layout Release for Module Update

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