[geardoc]

I know it generally forbidden, or at least frowned upon in head-fi, but I'm starting
to spend some real money on non-headphone stuff (amps, dacs, computer stuff) and need to know how strong my placebo effect has been on my shiny new toys. So, let me tell you a story...

I picked up one of these switchboxes at rat shack:
http://www.radioshack.com/sm-2-way-a...i-2049644.html
with the hopes of comparing a couple of amps. Before I got to that point I started by comparing my Chaintec AV710 with my nice outboard DAC (DAC-AH) in a blind ABX test with this switchbox. Switching back and forth with some music, I noticed a difference and tended to prefer the brighter sound of switch b which I found out later was connected to the external DAC. But, just for giggles, I ran a couple of sine waves thru, 440 and 1000Hz from Audacity. Lo and behold, the DAC-AH had a high frequency distortion or harmonic, I'm not sure. The well known and respected Chaintech line out was nice and pure sounding.

Update on 5/5: Put the DAC-AH on another computer system and ran the 1000Hz signal thru it. This time it was clean sounding. So, I conclude that the Chaintech AV-710 optical output is distorted, not the DAC. I'll verify this when my EMU DAC comes in.

What did I learn. Well, so much for using musical preference in a comparison! The music I preferred came out of the distorted DAC-AH. Maybe I thought the extra distorted sound added to the life of the music.

The lesson learned here, I guess, is to make sure and rule out garbage as a factor in comparisons.

This is my start. What have you ABX's lately?

 

[cotdt]

It doesn't need to be blind. Just doing an unblind A/B switch test reveals wonders on the differences in the sound equipment. But sometimes it reveals no differences at all.

 

[geardoc]

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif It doesn't need to be blind....

In a bar, I might nod my head and say sure, but in general, it does need to be blind to come to the right conclusion, eg. minimize bias. History is strewn with "facts" that turned out to be due to improper testing. I expect you won't be the first to try and whittle away at this tread and reduce it to the usual headfi opinion A versus opinion B, neither one based on any kind of controlled testing.

 

[Alleyman]

Quote:

It doesn't need to be blind

If it isn't blind then it's useless against testing placebo.

 

[cotdt]

Quote:

Originally Posted by Alleyman /img/forum/go_quote.gif If it isn't blind then it's useless against testing placebo.

you're switching back and forth between A and B via a switch. i don't see how one's imagination takes part when this happens. it is very different from hearing A and B at different times of the day, where imagination can indeed play a big role. when you do an A/B switch test, you compare two systems directly, without the interference of false memories and swinging moods.

i do run blind tests on myself, but over time i've found out that simply switching back and forth via a switchbox gives the same benefits and is more practical for reviewing equipment.

the role of placebo in audio is overstated, IMHO. i've accused others of hearing placebo, only to find out every time that they were right and i was wrong.

 

[agreenfield1]

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif you're switching back and forth between A and B via a switch. i don't see how one's imagination takes part when this happens. it is very different from hearing A and B at different times of the day, where imagination can indeed play a big role. when you do an A/B switch test, you compare two systems directly, without the interference of false memories and swinging moods.

I'm not disagreeing with you, but it is quite possible for ones imagination to truly affect how the sound is heard. A good example of this is the 'tick-tock' of a mechanical clock. At first it may sound like it is alternating between two different beats, when in fact it is repeating the same beat over and over. Depending on how you try to interpret the beats, you can hear it either way. Sort of an optical illusion for the ears.

 

[cotdt]

Quote:

Originally Posted by agreenfield1 /img/forum/go_quote.gif I'm not disagreeing with you, but it is quite possible for ones imagination to truly affect how the sound is heard. A good example of this is the 'tick-tock' of a mechanical clock. At first it may sound like it is alternating between two different beats, when in fact it is repeating the same beat over and over. Depending on how you try to interpret the beats, you can hear it either way. Sort of an optical illusion for the ears.

i see what you mean. i guess if the difference is extremely subtle, one's imagination can still play a role. but it is still useful for the person to see just how similar equipment A and equipment B sounds.

 

[geardoc]

Finally got my setup to double blind test two amps. Arranged a common source and split the inputs to the two amps, set levels with an SPL meter at 1000Hz, got my wife to switch the cables around while I left the room (or not), and without any interaction with her, set about to determine if I could tell A from B.

After an entire evening listening to most of my music genre's and several test tones, I'm enlightened. Now I know why this subject is taboo. Sorry for bringing it up.