OPERATION SECTION – CONTENTS 1. Introduction. 1.1 1.2 1.3 1.4 1.5 Input Channel Overview. Master Section Overview. Meterbridge. Options. Precautions. Page Number 2. Installation. 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 AC Mains Supply. Mic Inputs. Line Inputs. Insertion Points. Monitor Return Inputs. Tape/Direct Outputs. Meter Bridge Connection. Group Insertion Points. Group Outputs. Aux Outputs. Aux Returns. Main Stereo Output.
1. INTRODUCTION Congratulations on purchasing the TL Audio VTC (Valve Technology Console)! The VTC is a fully modular in-line multitrack mixer that offers all the benefits of the compact 8buss/multiple tape output format but with the supreme advantage of TL Audio’s critically acclaimed valve circuitry – which forms an integral part of the channel, monitor, group and master section signal paths.
1.1 INPUT CHANNEL OVERVIEW • Uncluttered Channel Preamp section containing a high quality low noise mic amp that combines an SSM 2017 solid state stage with an ECC83/12AX7A secondary valve stage, variable input gain (16 to 60dB), useful 90Hz high pass filter (12dB/octave), and switches for mic/line, phase reverse, and +48v phantom power. • A Tape Return Preamp featuring an ECC83/12AX7A valve stage, +/-20dB trim control, internal -10/+4dB level matching link and channel/monitor flip switch.
1.2 MASTER SECTION OVERVIEW The VTC Master Section is a triumph of intelligent, uncluttered design and contains: • Six Stereo Effects Returns on high quality Alps 60mm faders with control of Gain, AFL, and Mute. Post fade individual routing paths to both headphone outputs are provided, complete with an associated Level control for each headphone send. • A Headphone Matrix featuring two separate Phones outputs.
1.3 METERBRIDGE The standard integral VU meterbridge allows metering of all eight group and master L/R mix outputs. The standard calibration of these meters is such that 0VU corresponds to +4dBu of output, although this calibration is adjustable (see 4.16 of Technical Section). Each meter has an associated peak LED, which is calibrated to illuminate at +18dBu of output level: again this is adjustable (again, see 4.16 of Technical Section). 1.4 OPTIONS • High quality internal or external bantam patchbay.
1.5 PRECAUTIONS The TL Audio VTC requires a modest amount of installation, and like all electrical equipment, care must be taken to ensure safe, reliable operation.
2. INSTALLATION 2.1 AC Mains Supply. The mixer includes a separate T L Audio VR1000 power supply, and it is essential that only this supply is used to power the mixer. The power supply is fitted with an internationally approved 3 pin IEC connector. A mating socket with power cord is provided with the unit, wired as follows: Brown: Live. Blue: Neutral. Green/Yellow: Earth (Ground).
AUDIO CONNECTIONS – CHANNEL 2.2 Mic Inputs. Each channel has a female, 3 pin XLR connector for mic connection. It is compatible with either balanced or unbalanced signals, when the mating connector is 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”).
2.4 Insertion Points. The insertion points are also 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 point is unbalanced. 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. 2.5 Monitor Return Inputs. A 3 pin, 0.
- Screen = Ground. If unbalanced signals are used, the screen and ring should both be connected to ground. 2.7 Meter Bridge Connection The optional bar graph meterbridge is connected to each section of the VTC via these 25 way D-type connectors. See Technical Section 4.17 for more details. AUDIO CONNECTIONS – MASTER SECTION 2.8 Group Insertion Points. The group insertion points are interfaced via a 3 pin, 0.25” switched jack socket on the rear of the unit.
2.10 Aux Outputs. The Aux outputs are provided on unbalanced, 2 pin jack connectors. The mating connectors should be wired as follows: - Sleeve = Ground (screen), - Tip = Signal Phase (“+” or “hot”). 2.11 Aux Returns. Six stereo inputs are provided, for effects returns or other line level sources. The connectors are 3 pin jack sockets, and the mating connectors should be wired as follows: - Sleeve = Ground (screen), - Tip = Signal Phase (“+” or “hot”), - Ring = Signal Non-Phase (“-” or “cold”).
2.14 Master Insertion Points. The master 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 point is unbalanced. 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.
A stereo input is provided to the monitor section, to allow off-tape monitoring, etc. The inputs are via balanced, 3 pin jack connectors. The mating connectors should be wired as follows: - Sleeve = Ground (screen), - Tip = Signal Phase (“+” or “hot”), - Ring = Signal Non-Phase (“-” or “cold”). If an unbalanced signal is used, the screen and ring should both be connected to ground.
+48V 1 2 3 LINE PHASE 3. CHANNEL MODULE GAIN 4 5 7 FLIP 6 +48V 1 LINE 2 PHASE 3 MON TRIM AUX 1 On 8 2 9 On 3 On 4 On GAIN LINE OdB 11 4 5+6 AUX 3+4 PRE +16 +60 90Hz STEREO AUX PAN 7/8 FLIP 10 LEVEL On 5 7 MON TRIM PRE MIX B 6 H - MID +/- 12 -20 +20 Hz Q L - MID 3.
+48V LINE PHASE 2 1 3 mic set-ups. It is ‘pre’ Flip in the signal path so off-tape signals can be phase reversed if required by re-patching through the line input. 5 7 GAIN (4) GAIN 4 FLIP 6 MON TRIM AUX 1 On 8 9 2 On 3 On 4 On 11 5+6 AUX 3+4 The Gain control affects both line or microphone input level, dependent upon which is selected by the Mic/Line switch.
+48V 2 1 3 LINE PHASE GAIN 4 5 7 FLIP 6 MON TRIM The insert point is located on the main channel signal path, ‘post’ Flip and ‘pre’ EQ – and can therefore be used for processing the main channel signal when tracking, and the tape monitor signals when they are ‘Flipped’ through the main channel signal path during mixdown. 3.
+48V 2 1 3 LINE PHASE Used for stereo foldback GAIN 4 5 7 FLIP 6 MON TRIM Aux sends 3&4 can be routed to the Master Section’s two headphone mixes (Phones 1&2). Here they can be used exclusively or mixed with other signals, for example auxes 7&8, to create a headphone mix of both channel and tape monitor signals.
+48V 2 1 3 LINE PHASE GAIN 4 5 7 FLIP 6 MON TRIM AUX 1 On 8 2 On 3 On 4 On The VTC has been praised for its classic, ‘musical sounding’ EQ, capable of overall contouring, creative shaping and corrective treatments. The EQ stage shares the warmth, transparency and smoothness of the TL Audio’s outboard EQ units. The four band EQ comprises three sections, all within easy reach of the engineer: High Mid Parametric, Low Mid Parametric and HF/ LF Shelving.
+48V 2 1 3 LINE PHASE GAIN 4 5 7 FLIP 6 L-MID +/- MON TRIM AUX 1 On -15 8 2 On 3 On 4 On 200 9 50 11 +15 500 Hz 13 2K 5+6 AUX 3+4 PRE Cut/Boost C e n t r e 2kHz Q STEREO AUX PAN 7/8 10 LEVEL On PRE Q Frequency +/-15dB 50Hz - EQ ON 0.8 - 7.0 (1.25 - 0.15 octaves) MIX B H - MID LM Parametric EQ works in the same way as the HM band.
+48V 2 1 3 LINE PHASE GAIN PAN (16) 4 PAN 5 7 FLIP 6 MON TRIM AUX 1 On 8 9 2 On 3 On 4 On 11 The Monitor section is labelled ‘Mix B’ and 16 comprises a Pan pot , Mute switch, Signal Present and Peak LEDs, a Solo LED, 17 EQ assign switches, Source, Auto and Status switching, and a high quality 60mm Alps fader.
+48V 2 1 3 LINE PHASE GAIN 4 5 7 FLIP 6 In practice the red peak light is activated at a level of +18dB or above, allowing some advance warning when bringing up the monitor input gain before the headroom limit of +26dB is reached. MON TRIM SIGNAL PRESENT (19) AUX 1 On 8 9 2 On 3 On 4 On 11 5+6 AUX 3+4 This is a green LED which illuminates to show that a signal is present on the monitor channel path when it reaches a level of -30dB.
+48V 2 1 3 LINE PHASE GAIN 4 5 7 FLIP 6 MON TRIM AUTO (25) AUX 1 On 8 9 automation systems Status acts as a momentary switch intended to identify the presence of a signal path to the automation system computer - in effect, a ‘local status’ switch. If no automation is fitted then the Status switch has no effect on the audio signal.
+48V 2 1 3 LINE PHASE GAIN 4 5 7 FLIP 6 MON TRIM AUX 1 On 8 9 2 On 3 On 4 On 11 PRE STEREO AUX PAN 7/8 10 LEVEL On PRE MIX B H - MID +/- 12 28 Hz Q 30 SOLO The signal output from the pan pot can also be fed to the group routing buttons where it will act as an odd/ even signal feed. When panned left the signal path is fed to odd numbered groups (1,3,5 & 7), and when panned right feeds the even numbered groups (2,4,6 & 8).
+48V 2 1 3 LINE PHASE GAIN 4 5 7 FLIP 6 MON TRIM AUX 1 On 8 9 2 On 3 On 4 On 11 5+6 AUX 3+4 PRE Each channel solo switch activates PFL or SOLO IN PLACE mode (see Master Section for details of these two modes of operation, plus AFL – which applies to certain master section signals). In its default mode the solo switch will activate PFL mode (pre fade listen).
+48V 2 1 3 LINE PHASE channel tape outputs without any need for re-patching. GAIN 4 5 7 FLIP 6 MON TRIM AUX 1 On 8 9 2 On 3 On 4 On 11 5+6 AUX 3+4 PRE STEREO AUX PAN 7/8 ROUTING BUTTONS (34) As previously mentioned (in 27) the pan pot acts as an odd/even signal feed for the routing matrix.
MASTER SECTION 1 2 0 1 0 -00 +15 AUX MASTERS 4 0 3 0 -00 +15 -00 +15 -00 +15 PHONES 1 5 0 -00 6 7/8 0 0 +15 -00 +15 -00 LEVEL +15 AFL AFL AFL AFL AFL AFL AFL MUTE MUTE MUTE MUTE MUTE MUTE MUTE PFL C/ROOM MIX B OSC 3 AUX 3/4 AUX 7/8 PHONES 1 PHONES PHONES 1 1 PHONES 1 PHONES 1 PHONES LEVEL 1 EXT ON 2 2 BALANCE 2 2 BALANCE 2 BALANCE 2 BALANCE 2 BALANCE 4 1kHz 10kHz BALANCE PHONES 2 MIXB ASSIGN L+ R 0 L R L R L R L R L R L AFL AFL A
4. MASTER SECTION 4.1 AUXILIARY MASTER SENDS LEVEL At the top of the Master Section are the six mono and single stereo auxiliary send masters. All feature AFL and Mute switches, and a rotary fader which allows complete attenuation through to +15dB of gain, allowing a wide range of effects units to be driven. The circuitry is entirely solid-state and the auxiliary sends are provided on unbalanced 1/4 inch jack connections found on the rear panel master section.
The Mute button cuts the Stereo Return signal path but is not automatically muted when the SIP function is in operation. This allows the engineer to listen to Channel and Mix B sound sources and their effects by simply selecting a solo button on the input channel. Note that none of the Stereo Returns will be automatically muted while in SIP mode, but if the engineer wishes to monitor a source sound on the input channel with a single effect, a combination of SIP and AFL is possible.
Controls the output level of the Mix B signal. Up to +15dB of gain is available on the rotary master fader. This will control the amount of signal fed to both the Mix B outputs and the stereo L/R buss, should the Mix B signal be assigned to it (see below). ASSIGN LEFT+RIGHT If you wish to monitor Mix B and Main Channels simultaneously, signal from the Mix B buss may be routed to the Left/Right Bus by pressing the ‘Assign L+R’ switch.
Five stereo inputs are available on illuminated switches and can be selected individually or in combination: • L+R • Mix B • • • 2TA 2TB EXT This routes the main mix left and right outputs (post L+R fader) to the Control Room Monitor. This routes the Mix B left and right outputs (post Mix B master level) to the Control Room Monitor. This routes the 2TA left and right inputs to the Control Room Monitor.
PFL/AFL active is signalled by a red LED adjacent to the active switch, and by the yellow LED on the Master Module VU meter panel. When one or more is selected a signal override will cut in to replace the normal control room output with the dedicated PFL/AFL buss. SOLO IN PLACE When Solo In Place is selected in the Control Room Master Section, SIP replaces the PFL function of Main Channel and Mix B signal paths, but will not affect the Groups, Auxiliary Masters and Stereo Returns.
FOLLOW CR With this switch, the job of routing has been made even simpler for the engineer. When activated, the Studio output will automatically follow the Control Room source selection. SOLO The Solo switch routes the pre fade signal onto the PFL/AFL left and right busses, and activates the PFL/AFL override, or it will act as a Solo in Place switch if Solo Enable is selected in the Control Room section. 4.
monitor their respective group output signals. ON The group ON switches work in tandem with the group left/right switches above them as indicated by the desk legending. It enables the selected post fade group signal to be sent to the main mix outputs for traditional sub-grouping of signals such as drums and backing vocals. There are two choices: • ON • ON + L/R Post Fade group signal to main mix left and right outputs equally.
5. SPECIFICATIONS Input Impedance (electronically balanced) Mic input: All other inputs: 2.
2.3 2.4 Valve Replacement. Valve Path Identification. 39 3. 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Input Bays. Mechanical Construction. Adding Modules to Sub-fitted Consoles. Input Modules. Replacing Mute Switches. Input Circuit Description. Input Stages. Equaliser. Faders and Routing. Module Fault Finding. 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 Master Section. Mechanical Construction. Master Module Circuit Description. Master L+R Outputs. Group Outputs.
CAUTION: THE POWER SUPPLY AND CONSOLE CONTAIN HIGH VOLTAGES (UP TO 250V DC) AND HIGH POWER CAPACITY, WITH A RISK OF PERSONAL INJURY AND FIRE. SERVICE SHOULD BE PERFORMED BY COMPETENT QUALIFIED PERSONNEL, IN ACCORDANCE WITH CORRECT ENGINEERING PRACTICE. IF IN ANY DOUBT, REFER SERVICE TO THE RETAILER OR DISTRIBUTOR OF THE CONSOLE. The external power supply contains a transformer with a number of secondary windings. These secondaries are individually fused, rectified and smoothed.
Note that adjustment of “H+” by RV5 will also cause a change in H-, as the supply is centre tapped to 0V by R20 and R21. As the H- rail is bussed through the desk, some interaction of adjustment between bays may occur if re-adjusted in the console. When on load, some regulation of the heater supply may occur. This is acceptable as the valve circuits will continue to operate within their specifications with the heater voltage (H+ to H-) as low as 9V.
oscilloscope. Note that high impedance points such as the valve grids and anodes should not be probed directly, as the probe impedance may cause a misleading change in operating conditions. Some pointers to possible faults are listed in table 1 below: Table 1: PSU / Valve PCB fault symptoms and causes. Symptom. Hum on one or more signal paths. Possible cause. Check HT filtering components.
replacement as they age. When replacements do become necessary, they should be obtained from the console supplier. ECC83/12AX7A valves are quite commonly available, but the various manufacturers differ greatly in quality and audio performance, and replacement with the same type as originally supplied with the console will ensure consistency of performance.
3. Input Bays. 3.1. Mechanical Construction. The input modules are carried in a steel cradle which is mounted between the console bulkheads. The cradle provides mounting screw points for the modules, plus two rigid PCB backplanes into which the input modules are plugged. All connections to the input modules are made via a two part DIN41612 connector on each of the backplanes.
PC331 - Channel Module Input. CD1331 refers. PC332 - Channel Module Equaliser. CD1332 refers. PC333 - Channel Module Fader. CD1333 refers. Channel Module Overall circuit diagram: CD1350. See also the Channel Block Diagram in the specification section. The PCBs are interconnected with short, flat jumper cables. The mute switches and faders are wired to plug-in headers for ease of service replacement. 3.4. Replacing Mute switches.
The monitor input is connected to the balanced input stage, IC5A, and then to the pre-set gain stage, IC4B. The pre-set, RV11, is used to calibrate the module input by matching the monitor gain to the line input 0dB gain. It is only necessary to recalibrate RV11 if the input gain controls RV1 or RV2 have been replaced, and should be performed by feeding a 0dBu signal into the line input, setting the line and monitor gain pots to their centre detent, and noting the level at the insertion send.
automation systems may retain the module fader path - please refer to the automation system installer for details. The Stat (status) switches are also provided for use with certain automation systems only. They are momentary switches intended for identifying a signal path to the automation system computer. The channel and MixB paths may be routed to the equaliser section by switches SW5 and SW6.
apparent on various paths. Two valve positions, along with their associated trimmers and IC’s, are intentionally not fitted to PC345. The master front backplane, PC336, is linked to the input bay backplanes, PC337, by short IDC cables carrying the balanced busses. These cables plug into the underside of the PCBs, to avoid fouling the input modules.
4.4. Group Outputs. Refer to the expanded block diagram, fig 2. The Group mixes and outputs follow a similar path to the L+R outputs described above. The sub-mix for the groups consists of just the Talkback and Oscillator signals, routed onto PC336 as “TAPE +” and “TAPE -”. The mix amplifier for Group 1 is formed by IC3 and IC4A (see CD1336 sheet 2), and the valve stage on PC345 (“G1 VIN”, returned as “G1 VOUT”).
4.5. MixB Outputs. The MixB output signal path is again similar to the L+R outputs described above, except they do not have sub-mixes or insertion points. Refer to the expanded block diagram, fig 4. The mix amplifiers consist of IC9, 10 and 11 on PC336, feeding the valve stages on PC345 via the signals “MIXB L VIN” and “MIXB R VIN”. The outputs from the valve stages are routed to the MixB master level controls on PC348 as signals “MIXB L PRE” and “MIXB R PRE”, via the upper backplane, PC355.
CD1347. Following the balanced receiver stages IC2A and IC2B, the return is taken to the balance control, RV3, and buffered by IC4A and IC4B. The sensitivity of the returns is +4dBu by default, but may be changed to -10dBu by fitting jumpers J1 and J2. The stereo returns are controlled by a 60mm fader, followed by a +10dB buffer (IC3A and IC3B), and routed to the L+R sub-mix. Additional switches on PC347 also provide AFL monitoring and routing to the headphones. 4.8. Oscillator.
foldback mixing from both channel and MixB paths on the input modules. The sources for headphones 1 are mixed by IC2A and IC2B, and then controlled by the level pot RV1. The headphone outputs are directly driven by the high drive TLE2062 at IC1A and IC1B. These devices will directly drive headphones of 32ohms or higher impedance. The outputs are passed down to PC355 and out via the jacksocket PCB or patchbay.
routed via IDC cables and PC355 to the sub-mix on PC349 in the upper Master Module. The sub-mix adds in the locally sourced AFL signals from the Aux Send Masters and Stereo Returns. The signal “PFL L OUT” and “PFL R OUT” are routed back via PC355 to the Control Room and Studio output PCB, PC352, located on the lower Master Module front panel. 4.12. Control Room Output.
switch inner. Failure to ensure correct alignment may result in the switch cap springing off suddenly if the switch is operated quickly. The push buttons are controlled by similar circuits. For example, the Control Room “L+R” push button, SW2, is debounced by IC1B and toggled by the flip-flop IC2A (see CD1351 sheet 2). The output from IC2A is used to turn on the LED via Q2. The flip-flop array is initialised to a predetermined state at power-on by the “RESET” signal from IC15A.
The external monitoring inputs are routed off PC355 by the IDC cable at CN7, to the Control Room and Studio module, PC352. 4.16. Metering. The console is fitted as standard with retro-style VU meters for the eight groups plus left and right outputs. Each of these meters also has a peak LED adjacent to it. Control of the meters and LEDs is from PC344, located on the master section rear panel and connected to the backplane, PC355, by an IDC cable.
5. Calibration Procedure. For the first channel installed: 1. +4dBu 1KHz tone to LINE input, Gain @ 0dB, Channel Fader @ 0dB. BUSS switch off, EQ off. Trim Channel Valve for +4dBu @ DIR OUT. 2. Route to all Groups and L/R. Group and L/R Faders to 0dB. a): With Channel Pan fully left, trim Group 1/3/5/7 and L Valves for +4dB at their respective OUTPUTS. Trim 1/3/5/7 and L METERS for 0VU. b): With Channel Pan fully right, trim Group 2/4/6/8 and R Valves for +4dB at their respective OUTPUTS.