VOCE® EVC-1™ Product Manual

CONTENTS

Introduction Unpacking the EVC-1 Front Panel Rear Panel Usage Examples Stereo Linking 2 Units Side Chain Insert Specifications Warranty

Introduction

The VOCE® EVC-1™ Electron Valve Compressor is intended to be used as a "hi-fi" audio processing device which provides transparent audio dynamics range compression. It contains no solid-state components in the audio path; just audio transformers, photocells, and a vacuum tube with an external 300 volt B+ supply. A proprietary photocell circuit allows for an ultra-fast attack time (if desired) to process the audio with a lot of fast transients like drums but allows no high frequency loss in gain reduction.

Other features contained in the EVC-1 are: side-chain (key) listen switch, separate attack and release time controls, a side-chain insert jack, a stereo link connector, balanced input and output connectors (both 1/4" TRS and XLR) with ground lift switch, and high input impedance for interfacing to semi-professional equipment.

Unpacking the EVC-1

Inside the EVC-1 carton you will find the following:

  • EVC-1 unit
  • 6' power cable (for attachment to EVPS)
  • Owner's manual
  • Package of feet and mounting screw
  • Warranty card

Please return the warranty card soon after your purchase. This card will allow Voce to keep you informed of updates and new products.

Front Panel

VOCE EVC-1 Front Panel

  • THRESHOLD knob sets the level at which the compression will start to take effect. The counter clockwise position of this knobs starts signal compression at the lowest level.
  • ATTACK knob sets how quickly gain reduction will occur after it is called for. The counter clockwise position of this knobs is the fastest attack response.
  • RELEASE knob sets how quickly gain reduction will cease after the input signal falls below the threshold. The counter clockwise position of this knobs is the fastest release response.
  • RATIO knob is the amount of compression which occurs when the signal is above the threshold level. For a setting of 4:1, every 4 dB signal increase over the threshold level will result in only a 1 dB increase in signal output.
  • OUTPUT knob sets the output level.
  • BYPASS switch: "in" position bypasses signal. Compressor active is the "out" position.
  • SIDE CHAIN LISTEN switch: "in" position monitors the side chain signal. "out" position is normal.
  • METER switch: "in" position displays the output level on the meter. "out" position is displays the gain reduction level on the meter.

Rear Panel

VOCE EVC-1 Rear Panel

  • POWER SUPPLY: 7-pin DIN male connector for connection to high voltage power supply.
  • AUDIO INPUT XLR: Balanced +4 dBM line level audio input. May be unbalanced by grounding pin 3.
  • AUDIO OUTPUT XLR: Balanced +4 dBM line level audio output. May be unbalanced by grounding pin 3.
  • GROUND LIFT SWITCH: disconnects pin-1 from chassis ground on both outputs. Helpful for eliminating ground loop hum.
  • AUDIO INPUT 1/4" TRS connector: Balanced +4 dBM line level TRS (tip, ring, sleeve) 1/4" jack for audio input. May be unbalanced by grounding the ring connection.
  • AUDIO OUTPUT 1/4" TRS connector: Balanced +4 dBM line level TRS (tip, ring, sleeve) 1/4" jack for audio output. May be unbalanced by grounding the ring connection.
  • STEREO LINK 1/4" TRS connector: Use a phase flipped (tip and ring reversed) TRS patch cable to link two EVC-1s together for stereo operation. See chapter on stereo operation for more information.
  • SIDE CHAIN INSERT 1/4" TRS connector: Allows effects like EQ to be inserted into the side chain. Useful for de-essing. Tip is input. Ring is output.

Usage Examples

This section will describe some common studio applications for the EVC-1. There are many more which you will discover through experimentation.

SUBTLE VOCAL COMPRESSION

Threshold: 0 dB or where needed
Attack: 5 - 100 mS
Release: 100 - 500 mS
Ratio: 1.5:1 - 3:1

SNARE DRUM COMPRESSION

Threshold: 0 dB or where needed
Attack: 1 - 5 mS
Release: 20 - 200 mS
Ratio: 2:1 - 10:1

MIX HARD LIMITING

Threshold: -10 dB or where needed
Attack: 5 - 100 mS
Release: 100 - 500 mS
Ratio: 10:1

Stereo Linking 2 Units

Stereo linking of two EVC-1s is useful for compression of stereo mixes or other stereo program material. To link two units, connect both EVC-1s with a TRS phase flip cable to the STEREO LINK connector on each unit.

The cable is wired according to the following diagram:

EVC-1 Link Cable

It doesn't matter which end is connected to each unit. The cable ensures that the variable gain stages in each unit track properly. It is recommended that each EVC-1 be set the same during stereo operation.

Side Chain Insert

It's sometimes desirable to equalize the audio which controls the gain reduction of the EVC-1. This is the case for de'essing. Sibalent energy is contained in the 5-7 KHz range and can be reduced by making the side chain more sensitive to this frequency range. This can be done by connecting an equalizer to the EVC-1's side chain insert using a standard TRS insert cable. The EVC-1's side chain audio output is connected to the ring of the SIDE CHAIN INSERT connector and the side chain audio input is connect to the tip.

Specifications

  • Input Impedance: 100K Ohms
  • Output Impedance: 600 Ohms
  • Transformer balanced inputs and outputs with faraday shields
  • Headroom: +35 dBm output before clipping
  • Noise Floor: < -80 dBm "A" weighted
  • Gain: -infinity to 10 dB
  • Frequency Response: 18 Hz to 32 KHz
  • Distortion: < 0.6 % over entire frequency range @ +10 dBm output
  • Power Requirements: EVPS power supply (300 VDC and 12 VAC)
  • Size: 8" x 8-1/2" x 1-5/8"
  • Weight: 7 lbs