[LAD] A little quiz about audio measurements...

[Robin Gareus]

On 05/28/2010 05:05 PM, Robin Gareus wrote:
> On 05/28/2010 02:31 PM, fons at kokkinizita.net wrote:
>> Hello all,
>>
>> This week I had to perform measurements on a audio
>> interface, and this resulted in some quite interesting
>> results. Before revealing what happened, I'll let you
>> have a look at some of the data and come up with your
>> own conclusions, see
>>
>> <http://www.kokkinizita.net/linuxaudio/quiz.html>
>>
>> (Free beer at the next LAC for the best analysis)
>>
>> Ciao,
>>
> 
> Well, interpreting an 'experiment' that one has not conducted
> him/herself without knowing _all_ parameters of the setup is not
> something to encourage doing..
> 
> Did you use symmetric (XLR) connections? Are the sample-rate settings of
> both cards identical? what was the physical distance between the devices
> (cross-talk)? Was there any ground-lift equipment (built-in?) in place
> or maybe you simply forgot to switch off phantom-power?
> 
> Anyway, good that you've labeled it 'quiz'; so here's my guess:
> 
> You're encountering reflections (or even standing-waves) in the cable.
> (did you uncoil it? or was it a very short one?)

on 2nd thought (just been on the toilet) those could be in the order of
-75db but they would not yield a symmetric spectrum as you presented.

Sorry for the noise :)
robin

> Did you repeat the measurement? using different cables for example.
> 
> Cheers!
> robin
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