User`s Manual TUBE-TECH LCA 2B compressor and limiter
Contents
1. or decrease release of the input 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 5 mS 0 25 S pos 2 1 5 mS 0 8 S pos 3 3 mS 2 2 S pos 4 6 mS 50S 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 05S pos 5 6 for long peaks 4S pos 6 for continuously high levels 20S LIMITER ON OFF This switch defeats the limiter when in the aff position THRESHOLD The threshold is related to the output level and is continuously variable from off to OdBU Ratio 20 1 Attack 0 6 mS Release 05S 940530 LYDKRAFT ApS Mose All 20 DK 2610 R dovre Denmark CAUTION Bef ki ljust t let ti it heat t 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 OdBU to the input of the compressor 3 Turn the GAIN control fully clockwise 10 4 Adjust the preset GAIN P3 P103 lo2. supplied in dot mode This can be altered 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 10dB the output signal is only increased by 5dB 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 1dB The threshold is related to the output level and is continuously variable from off to 10dBU lf both the RATIO control and the THRESHOLD control are at thei i gt 15 1 lt 5dB 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
3. 5 W All specifications at RL 600Q Lydkraft reserves the right to alter specifications without prior notice LYDKRAFT ApS Mose All 20 DK 2610 R dovre Denmark 150130 JGP 940530 SYMPTOM CAUSE ACTION 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 Oscillations with no signal and max ratio and low threshold Unbalance in VCA tube Adjust balance Unbalance in VCA tube Adjust balance replace tube LYDKRAFT ApS Mose All 20 DK 2610 R dovre Denmark
4. LINK 1 LINK 2 on the front selects which 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 150205 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 6dB to 10dB 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
5. User s Manual TUBE TECH LCA 2B limit 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 si dechain 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
6. cated on amp psu PCB to an out put reading of_ 10 0dBU ADJUSTMENT OF GAINREDUCTION 1 Turn the THRESHOLD control for the compressor and limiter fully counter clockwise 2 Apply a signal of 0 0dBU 1 kHz to the input of the compressor 3 Adjust the GAIN control to an output reading of 0 0dBU 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 0dBU If this is not the case adjust the level with PZ P107 at the sidechain PCB to obtain a drop of 20 0dB The level might increase a little 0 5 to 1dB 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 1 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 control for the compressor and limiter fully counter clockwise 2 Apply a signal of 0 0dBU 1 kHz to the input of the compressor 3 Adjust the GAIN control to an output reading of 0 0dBU 4 Apply a DC voltage of 1 750 V into the sidechain jack socket tip 5 Set the LINK switch at LINK 1 and ob
7. mped to ground We recommend that the balance adjustment of the VCA should be carried out every 6 month NOTE 0 dBU 0 775V 941010 LYDKRAFT ApS Mose All 20 DK 2610 R dovre Denmark SPECIFICATIONS FOR LCA 2B 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 Gain Crosstalk 20 Hz 22 kHz CMRR 10 kHz Tracking 0 to 20 dB gain reduction LED display for gain reduction Compressor Ratio Threshold Attack manual Release manual Preset attack release Attack pos 1 1 5 mS pos 2 1 5 mS pos 3 3 mS pos 4 6 mS pos 5 3 mS pos 6 1 5 mS gt 2 kQ lt 600 lt 0 15 lt 0 15 gt 26 dBU 10 dB lt 80 dBU lt 70 dBU 5 Hz 40 kHz 6 dB 10 dB 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 Release 0 258 08S 2 28 508S 0 5 4 S 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 05S Ratio 20 1 LED indicating limiting Tubes 2xECC81 2xECC82 2xECC83 Dimensions H 2 units W 19 D 205 mm Weight 6 5 kg Power requirements 115V 230 V 50 60 Hz 30 4
8. serve that the output level has dropped to within 7 0dBU and 9 0dBU 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 OdBU 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 2 3 Turn the THRESHOLD control for the compressor and limiter fully counter clockwise and the GAIN control fully clockwise Switch the LINK switch to LINK 2 Apply a sine wave of 1 kHz 15dBU via a 1KQ resistor into the sidechain jack socket ring The 15dBU shall be measured before the 1KQ resistor Adjust trim pot P2 P102 located on amp psu PCB to a minimum reading at the output Reduce the level of the sine wave to 5dBU Adjust trim pot P1 P101 located on amp psu PCB to a minimum reading at the output Repeat step 3 6 When both adjustments are at minimum the level at the output shall be 15dBU less than 13dBU 5dBU less than 14dBU 5dBU less than 21dBU 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 resistor the negative part of the sine wave has been cla
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