I had emailed Joe with some questions regarding the LA500 kit I’m working on and he asked me to bring the discussion in here so here goes!
I’m a beginner and this is only my third or fourth DIY project. Having completed the kit, I put it into my 500 series rack and fed a 0dB, 1kHz tone into the LA500. I’m using Avid’s signal generator in pro tools, and a Saffire Pro24 DSP for my audio interface. I’ve got the LA500 set to the settings described in the calibration steps of the build thread. When I try to adjust the Meter 0VU trim pot to bring the meter to read 0 in the VU metering setting the trim pot seems to have no effect on the position of the needle in the meter. I’ve tried endlessly to adjust the trim pot with no change in needle position. I’m able to set and adjust the meter when it’s in “Meter GR” just fine, and the balance trim pot also seems to work when metering gain reduction. I’m not sure if this behavior is due to problems in my soldering or if the Meter 0VU trim pot could be a faulty component. Anyways, here are answers to questions that Joe asked in response to my original email along with pictures of the PCB’s + components.
Thanks in advanced for any help!
Q: Does the meter actually move down hard under -20 when you switch to
VU or is it just the same VU reading as in the off position? If it move down
hard when switched to VU you have some wires reversed to the meter.
A: It is the same VU reading as in the off position. If does not move past -20.
Q: Are you going to run this in 51X or 500 mode? You have the 2k7 on the MAC PCB so I presume 51X as this should be 1k8 for 500.
A: I have since clipped the 2k7 and will be using it in a 500 series rack.
Q: Can you hear the compressor working when listening to the output?
A: Yes, the compressor is able to attenuate the signal if I turn the threshold knob up.
Q: Does the makeup control add gain to the output?
A: Yes, the makeup control seems to be functioning normally as is able to add gain to the output.