TUBE-TECH LCA 2B compressor and limiter
Contents
1. 00Q 2xECC81 2xECC82 2xECC83 H 2 units W 19 D 205 mm 6 5 kg 30 45 W Lydkraft reserves the right to alter specifications without prior notice LYDKRAFT ApS Mose All 20 DK 2610 R dovre Denmark 941010 7 940530 SYMPTOM CAUSE CAC TION Noise Unbalance in VCA tube Adjust balance Noise Noisy VCA tube V1 V101 Replace and adjust Noise Control amp IC 4 IC 104 Replace Check gain reduction and readjust Hum 12V 110V 15V PSU Repair Overshoot when compressing Unbalance in VCA tube Adjust balance Oscillations with no signal and max ratio and low threshold Unbalance in VCA tube Adjust balance replace tube LYDKRAFT ApS Mose All 20 DK 2610 R dovre Denmark2. e preset GAIN P3 P103 located on amp psu PCB to an out put reading of 10 0 dBU ADJUSTMENT OF GAINREDUCTION 1 Turn the THRESHOLD control for the compressor and limiter fully counter clockwise 2 Apply a signal of 0 0 dBU 1 kHz to the input of the compressor 3 Adjust the GAIN control to an output reading of 0 0 dBU 4 Apply a DC voltage of 5 000 V into the sidechain jack socket tip 5 Set the LINK switch at LINK 1 and observe that the output level has dropped to 20 0 dBU If this is not the case adjust the level with P7 P107 at the sidechain PCB to obtain a drop of 20 0 dB The level might increase a little 0 5 to 1 dB from the instantaneously value within 5 10 sec This is quite normal 940530 4 LYDKRAFT ApS Mose All 20 DK 2610 R dovre Denmark ADJUSTMENT OF DISPLAY Turn the THRESHOLD control for the compressor and limiter fully counter clockwise 2 Apply a DC voltage of 5 000 V into the sidechain jack socket tip 3 Set the LINK switch at LINK 1 and observe that the 15 LED just turns off and the 20 LED is on 4 If this is not the case adjust P8 P108 at the sidechain PCB TEST OF TRACKING 1 Turn the THRESHOLD conrtrol for the compressor and limiter fully counter clockwise 2 Apply a signal of 0 0 dBU 1 kHz to the input of the compressor 3 Adjust the GAIN control to an output reading of 0 0 dBU 4 Apply a DC voltage of 1 750 V into the sidechain jack socket tip 5 Set
3. ich compressors are interconnected and on which bus they are connected If you select LINK 1 on both channels they will perform exact the same gainreduction Having several connected compressors in a rack you can select which compressors you will have working together By selecting e g LCA 2B no 1 ch 1 on link 1 LCA 2B no 2 ch 2 on link 1 and LCA 2B no 3 ch 1 on link 1 they are now interconnected and all three will perform the exact same compression The interconnection implies that the unit which performs the most compression is controlling the others To choose which one you want to control select the attack release time the threshold and the ratio on that unit and turn the threshold fully counter clockwise on the reminding compressors It is of course possible to have all the interconnected compressors control each other simultaneously 940530 LYDKRAFT ApS 1 Mose All 20 DK 2610 R dovre Denmark GAIN DISPLAY LINK SWITCH IN BYPASS COMPRESSOR RATIO THRESHOLD ATTACK RELEASE The gain control is used to adjust for the gain loss which takes place when the unit is compressing It is placed between VCA and output stage The gain control is continuously variable from 6 dB to 10 dB The green LED display shows the gainreduction for both the compressor and for the limiter A red LED shows if the limiter is active The display is from the factory supplied in dot mode This can be a
4. limi DESCRIPTION The TUBE TECH LCA 2B is a two channel unit with an independent compressor and limiter per channel The unit is all tubebased except for the power supply and sidechain circuit Output gaincontrol is placed between the VCA and output stage The VCA 1 dual triode is placed between the input transformer and the output stage 2 dual triodes The audio signal is picked up after the VCA and fed to the sidechain circuit The control signal from the compressor and from the limiter is combined and sent to the link switch and to the control amp which feeds the VCA The bi directional link busses are accessible at two 1 4 stereo jack sockets on the rear panel The channels can be linked together for stereo applications and also linked to other LCA 2B s via the two link busses and a standard stereo jack jack cord The compressor has six attack release presets as well as manual control The limiter attack release is fixed and equipped with an on off switch The LED display is fed from the control amp The limiter LED is fed from the limiter buffer The audio path is fully symmetrical from input to output Input and output have fully floating transformers All DC voltages are stabilised except the anode voltage for the output stage which is only filtered COMPRESSOR INTERCONNECTION The sidechain sockets for interconnection of several compressors are located on the rear panel A switch LINK 1 LINK 2 on the front selects wh
5. ltered to a bar by placing a strap on U6 U106 from pin 3 to pin 9 Interconnects several compressors on link 1 or link 2 If the compressor is left in the off position it works entirely independently This switch switches the compressor in and out of the signal path In the bypass position the entire unit is switch out The ratio control varies the ratio by which the input signal is compressed If the ratio selected is to 2 1 and the input signal increases 10 dB the output signal is only increased by 5 dB The ratio control is continuously variable from 1 6 1 to 20 1 The threshold is the point where the compressor begins its action It is defined as the point where the gain is reduced by 1 dB The threshold is related to the output level and is continuously variable from off to 10 dBU lf both the RATIO control and the THRESHOLD control are t thei i gt 15 1 lt 5 dB ti i expected The attack control chooses how fast slow the compressor responds to an increase in the input signal The attack control is continuously variable from 0 3 to 70 milliseconds The release control chooses how fast slow the compressor responds to a decrease in the input signal The release control is continuously variable from 0 07 to 2 seconds 940530 LYDKRAFT ApS Mose All 20 DK 2610 R dovre Denmark ATTACK RELEASE SELECT This switch selects how the compressor reacts to an increase attack or decrease release of the inpu
6. stor the negative part of the sine wave has been clamped to ground The balance adjustment of the VCA should be carried out every 6 month NOTE 0 dBU 0 775V 941010 6 LYDKRAFT ApS Mose All 20 DK 2610 R dovre Denmark SPECIFICATIONS FOR LCA 2B Gain Input impedance Output impedance Distortion THD n 40 Hz 0 dBU 10 dBU max output 1 THD n Noise Rg 200Q Gain 0dB 22 Hz 22 kHz lt 85 dBU CCIR 468 3 lt 75 dBU Frequency response 3 dB Crosstalk 20 Hz 22 kHz CMRR 10 kHz Tracking 0 to 20 dB gainreduction LED display for gain reduction Compressor Ratio Threshold Attack manual Release manual Preset attack release pos 1 pos 2 pos 3 pos 4 pos 5 pos 6 6 dB 10 dB gt 2 kQ lt 600 lt 0 15 lt 0 15 gt 26 dBU 10 dB lt 80 dBU lt 70 dBU 5 Hz 50 kHz lt 70 dB lt 60 dB 1 dB 0 dB to 20 dB 1 6 1 to 20 1 off to 10 dBU 0 2 to 70 mS 0 1to2S attack release 1 5 mS 0 25 S 1 5 mS 0 8 S 3 mS 2 28 6mS 50S 3mS 0 5 4 S 1 5 mS 0 5 4 20 S The release time in position 5 and 6 is program dependent that is pos 5 6 for short peaks 05S pos 5 6 for long peaks 4S pos 6 for continuously high levels 20S Limiter Threshold off to 0 dBU attack 0 6 mS release 0 5S ratio 20 1 LED indicating limiting Tubes Dimensions Weight Power requirements 115V 230 V 50 60 Hz All specifications at RL 6
7. t signal There are two settings of the switch 1 Manual Attack time from 0 3 mS to 10 mS Release time from 0 07 sec to 2 sec 2 Preset Attack Release pos 1 1 5mS 0 25 S pos 2 1 5 mS 0 8 S pos 3 3 mS 2 28 pos 4 6 mS 508S pos 5 3 mS 0 5 4 S pos 6 1 5 mS 0 5 4 20 S The release time in position 5 and 6 is program dependent that is pos 5 6 for short peaks 0 5S pos 5 6 for long peaks 4S pos 6 for continuously high levels 20 S LIMITER ON OFF This switch defeats the limiter when in the off position THRESHOLD The threshold is related to the output level and is continuously variable from off to 0 dBU Ratio 20 1 Attack 0 6 mS Release 05S w that the bal fiust tof the VCA i edoi 5 month 940530 LYDKRAFT ApS 2 Mose All 20 DK 2610 R dovre Denmark CAUTION Bef ki ljust tlett it heat up at least 30 mi Always check the DC voltages at the power supply When the VCA tube has been replaced adjustment of BASIC GAIN GAIN REDUCTION BALANCE shall be carried out The adjustment procedure refers to channel 1 The trim pots in brackets are for channel 2 At the sidechain jack sockets at the rear of the unit the tip is link 1 and the ring is link 2 ADJUSTMENT OF BASIC GAIN 1 Turn the THRESHOLD control for the compressor and limiter fully counter clockwise 2 Apply a signal of 1 kHz 0 0 dBU to the input of the compressor 3 Turn the GAIN control fully clockwise 10 4 Adjust th
8. the LINK switch at LINK 1 and observe that the output level has dropped to within 7 0 dBU and 9 0 dBU If this is not the case the VCA tube shall be rejected and replaced with a new one 940530 LYDKRAFT ApS 5 Mose All 20 DK 2610 R dovre Denmark ADJUSTMENT OF BALANCE IN THE VCA TUBE V1 V101 As a quick check of the balance of the VCA tube adjust the output to a level of O_dBU and turn the LIMITER THRESHOLD slow CW until the LIM led turns slightly on If the led turn on abruptly or starts oscillating the balance should be readjusted 1 Turn the THRESHOLD control for the compressor and limiter fully counter clockwise and the GAIN control fully clockwise 2 Switch the LINK switch to LINK 2 3 Apply a sine wave of 1 kHz 15 dBU via a 1KQ resistor into the sidechain jack socket ring The 15 dBU shall be measured before the 1KQ resistor 4 Adjust trim pot P2 P102 located on amp psu PCB to a minimum reading at the output 5 Reduce the level of the sine wave to 5 dBU 6 Adjust trim pot P1 P101 located on amp psu PCB to a minimum reading at the output 7 Repeat step 3 6 8 When both adjustments are at minimum the level at the output shall be 15 dBU less than 13 dBU 5 dBU less than 14 dBU 5 dBU less than 21 dBU If this cannot be obtained the VCA tube shall be rejected and replaced with new one If the sine wave from the oscillator is observed on oscilloscope after the 1KQ resi
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