Joe Malone wrote:OK is the master buss insert fully balanced +4dBM or unbalanced -10. As it should be easy to get meters to 0VU = +4dBM if balanced.wthrelfall wrote:Hi Joe.
So I've just got around to checking that the 2 units are tracking correctly when linked. I decided to re-calibrate first, but came across a strange problem - I'm sending a 1khz tone through my desk, meters are hitting 0db on the desk, patching the compressors to the master bus. I'm unable to get the meters to hit 0VU on the compressors, the pots will only let me get to -2db on both units. So I just increase the signal by 2db so that I can continue calibrating and check the link. Now I have another strange issue.. with the 2 units calibrated exactly (with 5db GR/VU showing and balanced as described in the instructions), it seems that to achieve the same amount of GR, one unit must have the threshold turned up much higher. I've attached a photo showing the 2 units, unlinked, attenuating the same signal by 10db to show the pot positions. When i then link the units, the units jump further apart, ie. the one compressing less compresses even less, the other compresses even more. I've attached another photo showing the difference in GR between the units when linked (right hand unit is the master with the new linking pot).
any thoughts?
The difference in threshold pots could be down to one threshold pot being linear and the other being log as some kits originally shipped with 100kB linear pots. All pull switch pots are 200k log and need both the front and back half of the pot paralleled to make a 100k log pot.
There is no master compressor when linking old style compressors. You must adjust both comps for the roughly same amount of compression on music before linking the 2 devices. With 1k tone into both comps and 5dB Gain reduction the meters should only deflect away from each other by a 1 or 2 db on each meter when linked which is fine and will not show on music signal. If error is greater first check mechanical -20 point on both meters is set the same with meter front adjustment before calibration then check calibration is not out of adjustment if both are ok then one of the optos may have settled to far out of range.
Since the release of the pull link switch version of the LA500 kit at the end of January this year 2012 we have started adding a 3 digital number to the side of the opto cells when we test them to make stereo pair matching better than it really needs to be. Even if the second unit is ordered at a later date with the 3 digit number we can match units.
Joe, thanks for your response.
Yes, it's an unbalanced insert point, my bad!
so with the compressors properly calibrated to 0vu direct from the main outs of the mixer (for calibration purposes), with 5db GR each and then linked, the comp with the pull switch jumps to -3.5db, the other to -8db. the mechanical -20 points on the meters are the same (can you explain how to do calibrate?).