Apogee AD-8000 Application Notes

Application Notes

The steps below describe how to calibrate soft limit on the AD-8000 using the oscillator on a
console or using test bench gear.
Soft Limit calibration procedure using a recording console
1. Calibrate the AD-8000 inputs to your optimum headroom setting using an oscillator via your
mix desk's stereo output, or any metered source (see AD-8000 manual for calibration
instructions).
2. Patch the oscillator into a mult on your patchbay (2-channel to 4-channel parallel).
3. Patch one set of outputs from your mult into two of the analog inputs of the AD-8000.
4. From the same mult, patch the other set of outputs into a line input of your mixing desk.
5. With Soft Limit turned off, set the oscillator to 1 kHz, increase the oscillator level to where the
"over" LEDs light up, then reduce the level until they just go out.
6. Making sure there is no signal processing (dynamics, EQ, effects, etc.) dialed into the mixing
desk's signal path, push up the line fader until the desk's stereo output meter reads the
threshold you wish to attain using the Soft Limit feature. The factory setting is –4 dBFS (i.e.,
4 dB under full-scale digital), so to check that it had been set correctly you would make your
stereo meter read -4. If you wish to decrease the threshold to –6, (2 dB more limiting,
effectively 2 dB more headroom) make the meter read –6. Alternatively, if you wish to
increase the threshold to –2, (2 dB less limiting) your meter should read –2.
7. Turn on Soft Limit.
8. Increase the oscillator output until the desk's stereo meter reads 0 VU (don't touch the
console fader at this point).
9. Remove the cover from the AD-8000 to expose the circuitry inside and find the SOFT LIMIT
adjustment pots. You will find them on the analog board labeled R33-1 through R22-8 (they
are eight silver cubes with white centers).
10. Now simply adjust the pots until each corresponding "over" LED lights then back off until
they just go out.
Apogee Electronics Corp Calibrating SOFT LIMIT
Product: AD-8000
Topic: Calibrating Soft Limit
Document #: 4
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