CONTENTS 1 2 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 INTRODUCTION PRECAUTIONS INSTALLATION AC Mains Supply Audio Inputs Unbalanced Line Inputs Instrument Inputs Insertion Points Balanced Outputs Unbalanced Output Ventilation OPERATION Input Select Input Gain High Pass Filter Phase Reverse Pad Phantom Power Drive and Peak LEDs Expander/Gate Section Gate Threshold Gate Attack and Release Gate Meter De-esser Section De-esser Depth De-esser Frequency De-esser Bandwidth De-esser Meter Compressor Section Comp. Threshold Comp. Attack & Release Comp. Ratio Comp. Gain Make-Up Comp. Knee Comp. Opto Mode Comp. Hold Mode 4.25 4.26 4.27 4.28 4.29 4.30 4.31 4.32 4.33 4.34 4.35 4.36 4.37 4.38 4.39 4.40 4.41 4.42 4.43 5 6 7 Equaliser Section LF & HF Bands LM & HM Bands LM/HM Frequency LM/HM Gain LM/HM Bandwidth EQ Pre Stereo Link Operation Ducking or Gating Peak Output Limiter Output Level VU Meter Digital Output Option Bit Rate Select Sampling Freq. Select Digital Output Meter Lock Status Output Formats Wordclock Input USER TIPS / FAQs SERVICE SPECIFICATIONS 1 INTRODUCTION Congratulations on purchasing the VP-1 Mono Valve Processor from TL Audio. The VP-1 combines classic Pentode and Triode valve techniques with Class A discrete and solid state circuitry to produce a unit providing comprehensive facilities for all aspects of single channel microphone and instrument pre-amplification and processing. The VP-1 features include: - Class A discrete and Valve pre-amplification, - Variable High Pass Filter, - Expander / Gate, - Vocal De-Esser, - Fully variable Compressor with Transconductance and Optical modes, - 4 band Parametric Equaliser, - Variable Threshold Optical Limiter, - Optional digital output, selectable up to 24bit, 96Khz. The block diagram of the VP-1 is shown in fig.1. There are four input sources: microphone XLR, balanced line +4dBu XLR, unbalanced line -10dBu jack and front panel instrument jack socket. The mic input features switchable 48V phantom power and 30dB pad, and is transformer coupled to both an all-valve pre-amp (consisting of pentode and triode stages) and a class A discrete pre-amp, providing two of the options on the input selector switch. The two line inputs are summed together for the third input selection, with the instrument input available as the fourth selection. The instrument input is front panel mounted for easy access, and is suitable for a variety of sources, including guitar, acoustic pickup and keyboard. The input stage sensitivity for the mic and instrument inputs is switchable in 10dB steps, followed by a +/-15dB trim control effective on all inputs. The input section also provides a continuously variable high pass filter to eliminate unwanted LF noise from the input source, and a phase reverse switch. An insertion point is provided immediately after the input section. The insertion point is unbalanced, at a nominal operating level of -2dBu. An expander/gate circuit is also included in the VP-1. The circuit provides variable threshold and attack and release times, and includes a four segment LED bargraph to indicate the gain reduction that is being applied. De-essing of vocal sources is provided, with the depth (i.e. attenuation) of the deessing variable, along with frequency and bandwidth tuning to match the sibilant content of the signal. This section also includes a four segment LED bargraph to indicate the gain reduction that is being applied. A comprehensive hybrid-valve compressor which can operate in either transconductance mode ("voltage controlled resistance") or optical mode ("light dependent resistance") is available to tailor the signal dynamics. The two modes each provide effective compression, but with subtly different characteristics which may suit particular source material. Hard or soft knee and optional hold switching further augment the fully variable threshold, ratio, attack, release and gain make-up. The VP-1 includes a four band equaliser, which utilises four triode valve stages. The EQ may be switched to pre or post the compressor. The LF and HF bands are shelving and feature switched frequencies, whilst the LM and HM bands are fully parametric peaking stages with variable frequency and bandwidth. All bands have +/-15dB of cut and boost. The master level control is a large rotary fader, providing up to 15dB of gain. An optical limiter with variable threshold and LED indication prevents the following equipment from being overdriven by the VP-1. Line level outputs are provided at +4dBu nominal level via a balanced XLR connector, and at -10dBu nominal level via an unbalanced jack socket. An optional digital output module is available for the VP-1, providing various output formats, word lengths and sampling rates. The VP-1 metering consists of an illuminated moving coil VU meter which can display input level, output level or compressor gain reduction. In addition, a variable intensity yellow "drive" LED indicates the signal level through the valve stages, and a red "peak" LED monitors the headroom remaining on the input and post processed signals. Please read this manual fully before installing or operating the processor. 2 PRECAUTIONS The TL Audio VP-1 processor requires very little installation, but like all electrical equipment, care must be taken to ensure reliable, safe operation. The following points should always be observed: - All mains wiring should be installed and checked by a qualified electrician, - Ensure the correct operating voltage is selected on the rear panel before connecting to the mains supply, - Never operate the unit with any cover removed, - Do not expose to rain or moisture, as this may present an electric shock hazard, - Replace the fuse with the correct type and rating only. Warning: This equipment must be earthed. 3 3.1 INSTALLATION AC Mains Supply. The equaliser is fitted with an internationally approved 3 pin IEC connector. A mating socket with power cord and mains plug is supplied. All mains wiring should be performed by a qualified electrician with all power switched off, and the earth connection must be used. Please note that when using this unit with alternate supply voltages (in foreign countries, for example) the position of the voltage selector switch on the rear of the unit may need adjusting. The unit may be set for 115V (accepting voltages in the range 110V to 120V, 60Hz AC) or to 230V (for voltages in the range 220V to 240V, 50Hz AC). The setting may be adjusted by inserting a small flat bladed screwdriver into the slot of the switch, and sliding the switch to the left (for 115V) or to the right (for 230V). Alternate supply voltages may also require a different power cable or mains plug. If in doubt, consult local electrical regulations. Warning: attempted operation on the wrong voltage setting, or with an incorrect fuse, will invalidate the warranty. 3.2 Audio Inputs. The VP-1 has two female, 3 pin XLR connectors, for mic and line sources. Both are compatible with either balanced or unbalanced signals, when the mating connectors are appropriately wired: Balanced inputs: - Pin 1 = Ground (screen). - Pin 2 = Signal Phase ("+" or "hot"). - Pin 3 = Signal Non-Phase ("-" or "cold"). Unbalanced inputs: - Pin 1 = Ground (screen) - Pin 2 = Signal Phase ("+" or "hot"). - Pin 3 = Signal Ground. When using unbalanced signals, the signal ground may be obtained by linking pins 1 and 3 in the mating XLR connector. Good quality screened cable should be used, particularly for microphone or low level sources, to prevent signal degradation and hum or noise pickup. 3.3 Unbalanced Line Inputs. An unbalanced line level input is provided for each channel, on a 0.25" mono jack socket. The mating plugs should be wired as follows: - Tip = Signal Phase ("+" or "hot"). - Screen = Ground. 3.4 Instrument Inputs. A 2 pin (mono) jack plug is required, which should be wired as follows: - Tip = Signal Phase ("+" or "hot"). - Screen = Ground. 3.5 Insertion Points. The insertion points are interfaced via a 3 pin, 0.25" switched jack socket on the rear of the unit. The pin connections are: - Sleeve = Ground, - Tip = Send, - Ring = Return. The insertion points are unbalanced, and operate at a nominal level of -2dBu . If used as an additional send only (e.g. as a send to a tape machine or monitor mixing desk), the Tip and Ring should be wired together, to preserve the signal path through the insertion point. 3.6 Balanced Output. The +4dBu balanced output is via a balanced, 3 pin male XLR connector. The mating connector should be wired as follows: - Pin 1 = Ground (screen), - Pin 2 = Signal Phase ("+" or "hot"), - Pin 3 = Signal Non-Phase ("-" or "cold"). If an unbalanced output is required from the XLR connector, pins 1 and 3 should both be connected to ground. 3.7 Unbalanced Output. An unbalanced line output at -10dBu is provided, on a 0.25" mono jack socket. The mating connector should be wired as follows: - Tip = Signal Phase ("+" or "hot"). - Screen = Ground. 3.8 Ventilation. The unit generates a small amount of heat internally, mainly due to the valve heaters. This heat should be allowed to dissipate by convection through the grill in the front panel, which must not be obstructed. Do not locate the processor where it will be subject to external heating, for example, in the hot air flow from a power amplifier or on a radiator. The VP-1 may be free standing, or mounted in a standard 19" rack where it will occupy 3U of space. 4 4.1 OPERATION Input Select. The VP-1 is designed to accept mic, line and instrument signals, and the relevant source is selected via a four position selector switch. The four positions are: Valve - selects the microphone input as the signal source, and feeds the mic signal through an all-valve preamp circuit. Class A - selects the microphone input as the signal source, and feeds the mic signal through a discrete class A solid state preamp circuit. Line - selects the line input as the source signal. Instrument - selects the front panel instrument input as the source signal. 4.2 Input Gain. The Mic and Instrument gains are set simultaneously in 10dB steps by the rotary switch, with fine adjustment available over an additional +/-15dB range from the trim control. The total maximum gain available on the mic input is +65dB. The gain available on the instrument input is 30dB lower than the mic, with a maximum of +35dB. The Line Input gain is set by the +/-15dB trim control only. 4.3 High Pass Filter (HPF). The high pass (low cut) filter is a second order circuit (12dB per octave), with -3dB points at the frequencies marked. The range of cut-off frequencies is fully variable between 25Hz and 1kHz. The high pass filter is active on all inputs, and is ideal for removing unwanted LF content from the input signal. Examples would be foot noise and traffic rumble being picked up by a microphone, or excessive low frequency response from a close mic'd source (known as the proximity effect). The filter is bypassable and a status LED indicates when the filter is active. 4.4 Phase Reverse. The phase reverse switch is used to invert the phase of the input signal, and like the HPF is active on all inputs. This could be required when processing a signal that is out of phase with other signals in a mix, in which case the resultant phase error typically appears as a loss of low frequency signal content, due to cancellation of out of phase components. If several VP-1s are used in a multi-microphone recording situation then some phase cancellation may occur between microphones, which the phase reverse switch will correct. 4.5 Pad. When activated, the pad switch will reduce the Mic input gain by 30dB. This is useful when dealing with high level mic input signals, such as those produced when recording loud sources with sensitive microphones (drums are a typical example). Without the pad, it's possible to overload the input stage in these circumstances, causing audible distortion. Activating the pad switch will cure this. 4.6 Phantom Power. This switch applies 48V phantom power to the mic input, allowing the VP-1 to be used with condenser microphones. CAUTION: Operation of the phantom power switch, or plugging a microphone in with phantom power applied, may cause a click or thump in your loudspeakers. To prevent this happening, ensure that the system gain is set to minimum (e.g. on your mixing console fader or power amplifier), before operating the switch or plugging in a microphone. 4.7 Drive and Peak LEDs. The yellow Drive LED provides a visual indication of the signal level through the valve stages, and therefore the extent of "warming" or valve character being introduced. The drive LED will gradually illuminate as the input level or gain is increased, over the range 0dB to +12dB. The red Peak LED operates as a conventional warning that clipping is about to occur. T ...