 Sunday, September 27, 2020 Register | Login        # A few ADDC measure facts and figures

In the ADDC measure an audio chain is the whole set of anything used to reproduce an audio signal: the signal source (like a CD player or similar stuff), DACs, preamplifiers, amplifiers, speakers, any kind of power and signal cables, power filters, environmental noise, operative conditions, equipments positions and so on. In general whatever is thought to have any effects on the reproduced signal falls into the chain.

## Some ADDC results obtained from a first chain Here are shown two reproduction error average values curves as a frequency function for a first given chain when a signal cable is inverted. Each curve is doubled as every measure has been made twice to be sure the differences were not due to any chain time variances. The vertical axe is the average percentage difference value with respect to the input amplitude, while the horizontal axe is the linear frequency axe from 100Hz to 13KHz. In this similar graph instead they are shown two reproduction error average values curves as a frequency function for the same chain inverting a power plug  phase. Each curve is here also doubled to be sure the differences were not due to any chain time variances. This and the above graph are very similar as typically the reproduction error shape is a sort of chain fingerprint, but the effects of the power phase and the signal cable inversion are somewhat different and perfectly detectable. This figure shows (in red and blue) the two reproduction errors in the time domain roughly from 242100 to 242800 µsec at 6.9 kHz, as the difference between the two average error values is roughly maximum at that frequency, as it can be seen in the previous graphs. In particular the red curve is obtained with the power plug position determining the smaller error. This three dimensional graph shows one of the two reproduction errors thought as both a time and a frequency function from 0.06 to 0.2 sec. and from 300Hz to 13KHz. Here you have the chain gain as both a time and a frequency function for the two power plug positions from 0.06 to 0.2 sec. and from 200Hz to 13KHz. It can be seen that the gain also changes in both time and frequency when rotating the DUT plug, and even if the amount of this difference is really small, the ADDC measure is able to show it with the greatest detail.

## Some other ADDC results obtained from another chain In this graph they are shown two reproduction error average values curves as a frequency function for a different chain using two different signal cables. Here also it can be seen the error shapes are similar as the reproduction error is always a sort of chain fingerprint. This time also each curve is doubled as every measure has been made twice to be sure the differences were not due to any chain time variances. The vertical axe is the average percentage difference value with respect to the input amplitude, the horizontal axe is the frequency from 100Hz to 13KHz. For the same chain it is shown how the chain frequency gain changes as well using the two different signal cables above mentioned. The vertical axe is in dB while the horizontal axe is the linear frequency axe from 100Hz to 7KHz. As usual the measures are made twice.