Aphex Expressor 651 - VCA 1001 trimming/adjustment
- Thread starter tonedude
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Help Support GroupDIY Audio Forum:
Measure distortion and control-voltage-breakthrough?
edit: Looking at a similar unit, the StudioDominatorII, it seems that these three pots are for nulling out control-voltage-breakthrough
Attached from that manual, 1/2
Jakob E.
edit: Looking at a similar unit, the StudioDominatorII, it seems that these three pots are for nulling out control-voltage-breakthrough
Attached from that manual, 1/2
Jakob E.
Attached from that manual, 2/2
Jakob E.
Jakob E.
I did the calibration following the guidlines in the second part (8.1.4 Shift Null). As it turned out I was lucky not using an external "sweep source" because I initially missread the text and thought it said 0 - 10 volt, but it actually says 0 - minus 10 volt... 
What I did instead was sending in an 1kHz signal in to sidechain return, I then set it up so I manualy could do the "sweep" from 0 dB to 20 dB gain reduction using the threshold pot. Seemed to work just fine. Measurments was done using a multimeter and Signalscope.
I was able to get the "shift" within 20mV sweeping with the threshold, and somewhere down to 1 or 2 mV when the unit did not compress. I don't know if that is considered good but I noticed that there is no measurable difference in distortion when getting close enought. It's kind of tricky adjusting the two trimpots on the Expressor because off the unpredictable interaction between them. I did trim VCA U104 first then VCA U109, then going back to U104 and so on... I think it's good enough. ;D 8)
What I did instead was sending in an 1kHz signal in to sidechain return, I then set it up so I manualy could do the "sweep" from 0 dB to 20 dB gain reduction using the threshold pot. Seemed to work just fine. Measurments was done using a multimeter and Signalscope.
I was able to get the "shift" within 20mV sweeping with the threshold, and somewhere down to 1 or 2 mV when the unit did not compress. I don't know if that is considered good but I noticed that there is no measurable difference in distortion when getting close enought. It's kind of tricky adjusting the two trimpots on the Expressor because off the unpredictable interaction between them. I did trim VCA U104 first then VCA U109, then going back to U104 and so on... I think it's good enough. ;D 8)
