DigiTUBE Single-Channel Tube Mic-Preamplifier with S/PDIF Output USER'S MANUAL 1.1 Copyright © 2001, PreSonus Audio Electronics, Inc. ALL RIGHTS RESERVED TABLE OF CONTENTS 1 1.1 1.2 2 2.1 2.1.1 2.1.2 2.2 2.2.1 2.2.2 2.3 2.3.1 2.4 3 4 Overview.................................................................................. 1 Introduction ............................................................................... 1 Features .................................................................................... 2 Controls & Operation................................................................ 4 Front Panel................................................................................. 4 Tube Preamp Section ................................................................... 4 Equalizer Section ........................................................................ 6 Back Panel ................................................................................. 9 Digital Section ............................................................................ 9 Analog Section............................................................................ 9 Vacuum Tubes .......................................................................... 12 Replacing the Vacuum Tube ........................................................ 10 Power Supply ........................................................................... 12 Technical Specifications ......................................................... 12 PreSonus Limited Warranties ................................................. 14 i OVERVIEW 1 1.1 INTRODUCTION Thank you for purchasing the PreSonus DigiTUBE Single-Channel Tube MicPreamplifier with S/PDIF Output. This preamp was designed using state of the art components to deliver crystal clear audio for an indefinate period of time. We believe the DigiTUBE to be an exceptional sounding unit and an exceptional value. Please contact us at 1-800-750-0323 with your questions or comments regarding this product. PreSonus Audio Electronics, Inc. is committed to constant product improvement and believes the best way to accomplish this task is by listening to the experts on our gear, our valued customers. We appreciate the support you have shown us through the purchase of this product. Please pay close attention to how you connect your DigiTUBE to your system. Improper grounding is the most common cause of noise problems found in studio or live sound systems. We urge you to scan this manual before hooking up your DigiTUBE to familiarize yourself with its features and applications. Good luck and enjoy your DigiTUBE! 1 1 OVERVIEW 1.2 FEATURES The following is a summary of your DigiTUBE's features: Dual Servo Gain Stage Your DigiTUBE contains a dual servo gain stage (no capacitors). This design provides ultra low noise performance and wide dynamic control. The DigiTUBE can boost the desirable signal without increasing unwanted background noise. Mic/Instrument/Line Input The DigiTUBE has a NeutrikTM combo (XLR & 1/4") connector. The XLR input can be used for microphone signals and phantom power is available for condenser mics when the 48V switch is engaged. The XLR will also accept line level signals when the PAD/LINE switch is engaged. The 1/4" input will accept instrument level signals, only. The PAD/LINE switch has no effect on the 1/4" input and it should be understood that the 1/4" input is not designed to accept line level signals. Pad/Line A switch on the front panel may be used to engage a -20dB pad for mic level signals or change the XLR input operating level from mic to line. Using the 20dB pad provides a more manageable signal from high output devices giving the operator greater control over the incoming signal and a much reduced chance of over-driving the input, thereby avoiding distortion. 48V The DigiTUBE has 48V phantom power available. Phantom power assures optimum performance from your condenser microphone without the need of an external power supply. A 80Hz switch is provided on the front panel of the DigiTUBE that enables the user to insert an 80Hz filter. Often referred to as a rumble filter, this feature is useful for eliminating bothersome low-end sounds such as air conditioning noise without greatly altering the desired audio. Parametric Equalizer The equalizer section is equipped with three dual concentric potentiometers The outer control selects the frequency and the inner control boosts/cuts the selected frequency. The EQ controls are LOW, MID, HI from left to right. The bandwidths are broad enough and have enough overlap to allow a very effective contour of the incoming audio signal. 2 OVERVIEW 1 Drive The DigiTUBE is provided with a DRIVE potentiometer for controlling the amount of signal routed through the 12AX7 vacuum tube. This feature lets you control how much saturation of the signal occurs. Greater levels of tube saturation give the signal greater warmth and a richer sound. This feature works equally well on mics and instruments and is just what is needed to tame that `brittle' sound encountered with different types of digital media. Internal Clock An internal clock is provided for 44.1 kHz or 48 kHz operation selectable by way of the switch on the back panel. An INTERNAL/EXTRERNAL selector and a BNC connector for external clock input can be found on the back panel as well as the S/PDIF connector for the DigiTUBE's digital output. 3 2 CONTROLS & OPERATION 2.1 FRONT PANEL The front panel of the DigiTUBE contains: POWER OUTPUT LEVEL (dBu) -42 -36 -30 -24 -18 -12 -6 -3 0 3 6 9 0 120 12 15 18 24 TUBE PREAMP 5 24 EQUALIZER 0 2k 0 5k PAD/ LINE 0 10 3 48 48V GAIN (dB) -12 30 80Hz LOW 1k +12 -12 900 EQ IN MID 5k +12 -12 3k DRIVE MIC/INSTRUMENT LINE HIGH 15k +12 LEVEL FREQ The front panel of the DigiTUBE is divided into two sections: the tube preamp controls are located on the left hand side of the unit's front panel and the equalizer section is on the right. 2.1.1 TUBE PREAMP SECTION NeutrikTM Combo Microphone (XLR) / Instrument (1/4") Input Drive Control Pad/Line Switch Gain Control (3dB - 48dB) +48V Phantom Power Switch Mic/Line/Instrument Input The DigiTUBE has a NeutrikTM combo connector which provides both an XLR and a 1/4" TS input. The XLR connector can accept microphones or by engaging the PAD/LINE switch, line level signals. The 1/4" input is for instrument level signals only. If you wish to adapt a line level device with a 1/4" connector, An XLR connector with pins 1 and 3 tied together for ground and the hot connected to pin 2 must be made. This adapts the unbalanced line level cable to input signal via the XLR input and the PAD/LINE switch to convert the input to accept a line level signal. Drive The DRIVE potentiometer controls how much signal is routed through the 12AX7 vacuum tube. The effect achieved by this procedure can be subtle to extreme, depending on the setting being used. A `warming up' of the sound can be noticed at lower settings. This effect can be used to compensate for the harshness commonly encountered in digital signals with M ORE 5 0 10 4 CONTROLS & OPERATION 2 the resulting sound possessing a `richer' and `sweeter' tone. If an overdriven signal is desired, this can be achieved by significantly raising the level of the DRIVE control. Overdriving the tube is especially useful for direct electric guitar sounds. Setting the DRIVE control is a matter of taste; the amount of saturation needed to achieve a desired result depends upon the resulting sound you want to hear. Experiment! Gain This control is used to determine the amount that a 24 signal being processed by the pre-amplifier is increased in level at output. Dynamic mics and instruments without pre-amps may require more gain than condenser mics and instruments that have a built-in 3 48 pre-amp (care should be taken with instruments having their own built-in pre-amp not to overdrive the 1/4" input of the DigiTUBE). Line level signals can only be processed through the XLR input connector with the PAD/LINE switch in the LINE position. Attempting to use the 1/4" input for line level signals exceeds the design parameters of the DigiTUBE. The 1/4" input of the NeutrikTM connector is designed to accept instrument level signals and attempting to use the 1/4" input for line level will likely yield an unsatisfactory result. Activating the PAD/LINE switch reduces the incoming signal by 30dB. This is a very useful feature for rapidly reducing the level coming into the DigiTUBE to prevent the input signal from over-modulating (distorting). This may occur due to a high output level from a microphone. Padding the mic input serves to provide increased `headroom' for the operator and allow greater variance in adjusting the GAIN control. Placing the switch to the PAD/LINE position allows the XLR connector to accept line level signals. Line level signals can be used in the XLR input without overdriving the input. Keyboards and other line level devices can be inserted into the DigiTUBE XLR input by selecting the LINE position. M ORE Note: the PAD/LINE switch does not affect the 1/4" input of the NeutrikTM connector. The 1/4" input is designed to accept instrument level signals ONLY! 5 2 CONTROLS & OPERATION Input Phantom power is available through the XLR input of the DigiTUBE. This 48V of phantom power is for condensor mics and/or any other devices that may require it via XLR inputs. 1 3 2 PIN 1 = GND PIN 2 = + (+48V) PIN 3 = - (+48V) 2.1.2 EQUALIZER SECTION Low (30Hz - 1kHz) +/- 12dB Mid (900Hz - 5kHz) +/-12dB High (3kHz - 15kHz) +/-12dB 80Hz Switch EQ IN Switch Low The LOW control is a dual concentric potentiometer with the outer ring allowing the selected frequency to be boost or cut by as much as twelve decibels. The straight up, twelve o'clock, position is labeled zero 30 1k (0). When the outer control knob is in this position, -12 +12 no effect is exerted on the signal, regardless of what frequency is selected with the inner controller. Rotating the outer control knob to the left or counter-clockwise reduces the selected frequency. Rotating the outer controller to the right or clockwise increases the selected frequency. The inner control knob selects the frequency. The LOW EQ control goes from 30Hz to 1kHz. The control frequency is narrower to the fully counter-clockwise or left side. As the inner control is rotated clockwise, the frequency bandwidth is much more broadly defined. For example, from the fully counter-clockwise position of 30Hz to the first mark represents a difference of 10Hz - 15Hz whereas from fully clockwise or 1kHz to the first marked position back represents as much as a 100Hz difference. The significance of this to the operator is that a movement of the frequency selector from a fully counter-clockwise position to approximately the twelve o'clock position represents smaller incremental frequency changes compared to the frequency changes that occur when the selector travels clockwise past the twelve o'clock position and beyond. LE SS 0 120 E OR M 6 CONTROLS & OPERATION 2 Mid The dual concentric potentiometer labeled MID controls the frequencies from 900Hz to 5kHz. The outer ring provides boost or cut at the frequency selected by the inner knob by plus or minus twelve decibels with the 5k straight-up noon position equal to zero or no boost or -12 900 +12 cut. The inner control knob begins at 900Hz in the left or fully counter-clockwise position and continues to 5kHz in the right or fully clockwise position. This control behaves in the same manner as the LOW control with the frequency widths delineated by the knob's markings becoming wider as the knob travels to the right or the clockwise direction. LE SS 0 2k E OR M LE SS 0 5k -12 3k 15k +12 High The Equalizer dual concentric control labeled HIGH operates in the same manner as the LOW and MID controller. The inner HIGH control knob is used to boost or cut frequencies ranging from 3kHz to 15kHz by as much as 12dB by adjusting the outer ring of the controller. 80Hz Switch The DigiTUBE equalizer section contains a switch labeled 80Hz. Engaging this switch activates an 80Hz filter (often referred to as a rumble filter). This filter is useful for eliminating extraneous low-end sounds from the signal being amplified. Frequencies from 80Hz and below are cut from the incoming signal. This will eliminate low-frequency noises such as air-conditioning hum or the sounds of nearby traffic or other vibrations that may be transmitted through the microphone stand into the microphone. It can also be useful for reducing the effect of electrical hum that may be the result of grounding problems. EQ In The EQ IN switch provides the ability to audition the effect that the equalizer is having on the signal being processed. Pushing the switch to the latched position inserts the equalizer into the signal path. Releasing the switch takes the EQ out of the signal path. You can qui ...