Remove input signal and (re)set “GR meter Zero” for a reading of 0dBVU. Now set the “GR meter Trck” trimmer so the VU-meter reads -6dBVU. When you reach a point where output level is half the input level, you have 6dB of gain reduction in the unit. Slowly turn up the level of your input signal (at the signal source, not with the input level control) while you monitor both input- and output levels with a voltmeter. Set output level so you get 50mV at the output also (now you have unity gain). Adjust untill meter reads 0dBVU.Ĥ: “GR meter Trck” (tracking). Somehow this is not an important adjustment soundwise.ģ: “GR meter Zero”. If you have no ter, simply set at middle position. Bypass the unit, input a ~1kHz, ~0dB signal, set unit gain to unity (by input- and output controls), and set trimmer for minimum distortion. This sets the FET start point in the beginning of it’s conducting range.Ģ: “Dist. This is set by bypassing the unit, putting through a signal, adjusting in- and outlevel so output is around +1dB, and adjusting the trimmer untill a level drop of 1dB is acheived. But that is not easy to follow, so here’s a simplified adjustment procedure:ġ: “Q Bias”. So when they say “turn attack fully counterclockwise to bypass”, it could translate into something like “bypass the unit with the meter switch”. pdf manual, but that could be a bit tricky because we changed the bypass to be on the meter switch in stead of on the attack switch. You could use the procedure from the original. – Once the unit is built and checked, proceed with the adjustment procedure. The input transformer option is there simply because I like what it does for the sound. The “real” 1176 LN rev#F uses the electronically balanced input. – Note that the LL1540 input transformer is OPTIONAL. Here you can also connect the mains power ground from the IEC power connector if you need that. – Connect 0V/Ground to chassis at – and only at – the input XLR(F) connector. – Make sure that the center tap of the 2x24V at the power transformer is connected to ground If they have been mounted wrong and powered up once, there’s a good chance they are destroyed. – Remember that transistors aren’t very forgiving. – Check and double-check the PCB for shorts and solder blobs before powering up. – Use a heat sink for the 7824 voltage regulator. – If using NTE substitutes for semiconductors, make absolutely sure that they are actually also pin-compatible. Check especially resistors with an Ohm-meter. – Check component values before soldering in. But there are some common errors that you should avoid: Quite a lot of people have succeeded till now. You can find the schematic, parts list, and component layout under the “documentation” tab above. Each PCB set comes individually bagged and sealed to protect solder traces during shipping. All of our PCBs are manufactured to the highest quality standards. The Gyraf 1176 PCB kit is the best starting point for building your own DIY 1176 Compressor.
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