Calibrating Hairball Audio 1176 Rev D to Original UREI 1176 Rev D

Hey guys,

I'm currently almost done building my Hairball 1176 Rev D, I just need to start calibrating it.

I am undergoing my bachelor year and as my final I chose to compare a DIY 1176 to the UREI 1176.

I will be renting out an original UREI 1176 and will be running harmonic distortion tests, phase tests, & blind listening tests to analyze and compare the differences between both compressors.

As I am by no means an expert in electrical engineering, I figured I'd ask you guys how to go about matching the calibration of the original rented unit to my unit (meaning reading the exact same values and applying the same amount of compression for the testing stage, this would give the tests a more accurate result).

If any body has any suggestions or has tried this before, then please don't hesitate to let me know!

Thanks!

NOTE: Also i wasn't sure if I should post this in The Lab section, The Chamber section, or the Drawing Board section, so i posted it here. If this is not appropriate than please do say so!

I am very interesting to see your results, I hope you post them here.

What test equipment and setup are you using for the measurements? The test signal source and distortion analyzer will need 600 ohm source and load impedances. That will present the worst case conditions for both units (harder to drive 600 ohm loads than bridging loads).

As for calibration, seems you would need to follow the procedure outlined in the Hairball build or the one published by UREI on both units. Test tone generator, VU meter or true RMS voltometer are required for that.

I bought a QA401 a few months back and discovered measuring this kind of gear is a little more complicated that it first appears.

Well the JBL pro audio site has the original calibreation specs. I am now on my 6th Hairball Audio build. And the procedure on his site works fine. I have been in studios that have the old ones. They sound old. These sound cristal clear with some warmth. Awesome! Just what I need after my pres!

Thanks,
John