Author Topic: AES17 - Level-dependent logarithmic gain (AKA Linearity Test)  (Read 322 times)

David Samborsky

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AES17 - Level-dependent logarithmic gain (AKA Linearity Test)
« on: September 25, 2020, 08:34:20 AM »
Level-dependent logarithmic gain
Applies to: EUTs with analogue or digital inputs and analogue or digital outputs.

Aim: To measure the change in gain of the EUT with signal amplitude, sometimes called 'deviation
from level linearity'.

Method
A 997Hz sinusoidal stimulus is applied at 5dBFS. The output of the EUT is measured after passing
through a 1/3 octave 997Hz band-pass filter. The gain of the EUT is calculated as being the ratio of its
output amplitude to its input amplitude. The narrow-band noise floor of the EUT is also measured
using the same band-pass filter, but with the stimulus muted.
The stimulus is reapplied, and its amplitude is then reduced in 5dB steps, until it is within 5dB of the
measured narrow-band noise floor, noting the output amplitude at each step and calculating the
inferred EUT gain. The results are graphed for each channel, with relativity to the gain measured at
5dBFS expressed in dB, as a function of the applied amplitude. At the end of the test, a worst-case
gain deviation (in dB) is also reported for each channel.
When the A/D and D/A portions are available separately, this test should be repeated for each section
independently.

Conclusion:
The Ultimate Preamplifier exhibits exception linearity all of the way down to -130dBFS yielding at least 22 bits of resolution !

References
http://resources.prismsound.com/tm/dS3_Applications_Manual_A4nc.pdf
« Last Edit: September 30, 2020, 10:16:18 AM by David Samborsky »
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David Samborsky

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Re: AES17 - Level-dependent logarithmic gain (AKA Linearity Test)
« Reply #1 on: September 25, 2020, 08:35:42 AM »
-5dBFS to -120dBFS range matches testing done by ASR



-5dBFS to -140dBFS full range AES17 test

« Last Edit: September 25, 2020, 09:21:55 AM by David Samborsky »
The home of the Ultimate-Preamplifier and Ultimate-Amplifier ! https://www.analog-precision.com/