Waveform Fun! Amp/Headphone output comparison

[purrin]

Quote:

Instead of looking at signal graphs, run them through Bill Waslo's Audio DiffMaker.
 
se

 
Great idea. I was about to write my own code.

 

[ultrabike]

Quote:

Instead of looking at signal graphs, run them through Bill Waslo's Audio DiffMaker.
 
se

 
Wow! I think that one comes with a FR Analyzer!
 
All of this would be really interesting (to me at least) since it may help explain amp - headphone synergies. Very nice!
 
By just eye-balling it, it seem to me the middle one (Amp A + HD800) is a tad bit brighter than the bottom one (Amp B + HD800).

 

[MomijiTMO]

By just eye-balling it, it seem to me the middle one (Amp A + HD800) is a tad bit brighter than the bottom one (Amp B + HD800).

I'm home sick so I might be slow but I thought the bottom one was the original?

 

[nick_charles]

Quote:

 
Wow! I think that one comes with a FR Analyzer!
 
All of this would be really interesting (to me at least) since it may help explain amp - headphone synergies. Very nice!
 
By just eye-balling it, it seem to me the middle one (Amp A + HD800) is a tad bit brighter than the bottom one (Amp B + HD800).

 
The horizontal axis is time and the vertical is amplitude , it is not a spectrum but the Op could run it through a spectrum analyzer such as that in Audacity then you can export the amplitude at each frequency as a text file and graph it in Excel or similar and also do math on the differences
 
@op - When I ahve done these things before I have found it useful to do multiple measures and then aggregate the results, it helps control for random variation which you will find is a potential issue with both ADCs and mic placement - running 10or so trials is admittedly tedious but you get more reliable results...

 

[nick_charles]

Quote:

 
Great idea. I was about to write my own code.

 
 
Word of caution here, I've used diffmaker a lot. Before you try it out in anger try it with two identical copies of the same audio file. In the past DM has found differences for me between identical files which makes it iffy

 

[ultrabike]

Quote:

 
The horizontal axis is time and the vertical is amplitude , it is not a spectrum but the Op could run it through a spectrum analyzer such as that in Audacity then you can export the amplitude at each frequency as a text file and graph it in Excel or similar and also do math on the differences
 
@op - When I ahve done these things before I have found it useful to do multiple measures and then aggregate the results, it helps control for random variation which you will find is a potential issue with both ADCs and mic placement - running 10or so trials is admittedly tedious but you get more reliable results...

 
I know Nick, I was just not clear on my post as usual. What happened is that I went to this website (Steve Eddy's suggested Bill Waslo's Audio DiffMaker): http://www.libinst.com/Detecting%20Differences%20%28slides%29.pdf and I think that under slide 13 they talk about what appears to be their built in Spectrum Analyzer.
 
Quote:

I'm home sick so I might be slow but I thought the bottom one was the original?

 
Thanks. I may have read it wrong but it said "1) original wav file; 2) amp A; 3) amp B" So I guessed 1) is the top... I think I read it wrong though

 

[jcx]

anyone trying to make sense of this sort of testing probably needs to read Both Pages of http://www.innerfidelity.com/content/expert-tests-innerfidelitys-headphone-measurement-repeatability-and-reproducibility
 
 
you can also find Tyll's square wave measurements - unlike a music clip we actually know what square waves should look like, relations are simple enough to do some rough translations between time response and frequency response

 

[purrin]

Quote:

 
 
Word of caution here, I've used diffmaker a lot. Before you try it out in anger try it with two identical copies of the same audio file. In the past DM has found differences for me between identical files which makes it iffy

 
Heh, yeah, just found out. I will be writing my own code.
 
Quote:

 
I know Nick, I was just not clear on my post as usual. What happened is that I went to this website (Steve Eddy's suggested Bill Waslo's Audio DiffMaker): http://www.libinst.com/Detecting%20Differences%20%28slides%29.pdf and I think that under slide 13 they talk about what appears to be their built in Spectrum Analyzer.
 
 
Thanks. I may have read it wrong but it said "1) original wav file; 2) amp A; 3) amp B" So I guessed 1) is the top... I think I read it wrong though

 
LOL, the bottom one is the original. I think.

 

[frenchbat]

Thanks Purrin, you picked my interest here.
 

Spoiler: Warning%3A%20Spoiler!

Funny enough, I have the feeling that depending on which part of the graph you're looking at, the answer might be different. For example, the higher the amplitude of the wave, the more up and bottom graphs look alike. However, with a lower amplitude, the middle graph looks more like the top graph.

If the original is the bottom one though, I'm totally wrong or the likeness is not linked to the source itself. Maybe the ADC or the mic.

 

[n3rdling]

Are those single runs on each amp or an average of multiple runs?  Also, what is the time scale?

 

[purrin]

Single runs not averaged or anything. I have data for a few more runs. Time scale - each block is a sample at 44.1kHz

 

[xnor]

Why don't you leave out the mic and record directly the output of the amp (driving both the headphones and line-in)?

 

[purrin]

I can and will do that too. These things take a lot of time to set up right.