non-sighted evaluation of operational amplifier / op-amp / IC chips
Jun 2, 2012 at 9:23 PM Thread Starter Post #1 of 12

kiteki

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Hi,
 
I think listening to music / audio is by it's nature blind, not sighted, so I'd like to evaluate some op-amp's in an amplifier without seeing them.
 
 
It's pretty simple, all I need is a multi-channel amplifier like this,
 

 
 
The Behringer HA400 one has four channels, with one op-amp on each, NJM4580.
 
So the process is
 
- acquire new op-amp's of identical shape and size
 
- shake them inside a bubble-wrap padded box
 
- install them in pitch darkness (randomly) with sunglasses on
 
- listen and take notes
 
- open
 
 
Pretty simple process.
 
 
Ran into an issue here - http://kunekune.at.webry.info/200903/article_1.html
 
They're all soldered on, I need a cheap multi-channel amplifier with socketed IC's, any links?
 
Thx.
 
Jun 3, 2012 at 4:54 AM Post #3 of 12

e19650826

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the better procedure would be have two separate rooms. get a very long interconnect. and find three people. One person randomly switches the amp in one room while another person listens through one headphone at all times in another room. The last person gives command such as "trial one starts" "trial one stops" and etc. without knowing which amp the person in the "amp room" is switching on.
Then you would have a Double Blind test, which is much more reliable than your procedure.
To perfect this experiment, all you need is 500 more subjects for audition, and you will have a non-refutable result.
 
EDIT: you can also have some fun with this procedure. like deliberately tell the person who is listening that you are swtiching amps while not switching to see if cognitive understanding affect the brain's interpetation of the sound source.
 
Jun 3, 2012 at 9:52 AM Post #4 of 12

firev1

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I doubt there would be such a multi channel amp(even so its probably diy), if I could get one, I would desolder them myself and socket them though. Maybe the breadboard style Cmoy will be better? At the very least, for the opamps, I would at least select low impedance opamps. 
 
Jun 3, 2012 at 10:10 AM Post #5 of 12

Shike

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I'd be concerned of poor layout and implementation for the new opamps.  Implementation is everything, and what works well for one opamp may throw the others into oscillation.
 
Jun 3, 2012 at 10:24 AM Post #6 of 12

firev1

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Quote:
I'd be concerned of poor layout and implementation for the new opamps.  Implementation is everything, and what works well for one opamp may throw the others into oscillation.

A controlled test with slower opamps will have to do then. Testing the modern OPA series will run into these problems + high impedance effects.
 
Jun 3, 2012 at 10:45 AM Post #7 of 12

mikeaj

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I'm not sure about very long interconnects, particularly with some op amps that might not be so stable.
 
Instead of looking for multichannel amps, how about just two different amps?  You can use the "blind" installation still.  Yeah, maybe CMoys with unity gain stable op amps and low gain, maybe even 1x.  For a CMoy, there are a lot of people who know what works, and a lot of opinions on what is better, so there's some knowledge base / mythology to work with.
 
One problem with blind installation is that you still need to put the op amps in the correct way.  Hopefully they all have the notch in the same place.
 
Jun 3, 2012 at 6:21 PM Post #8 of 12

kiteki

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the better procedure would be have two separate rooms. get a very long interconnect. and find three people. One person randomly switches the amp in one room while another person listens through one headphone at all times in another room. The last person gives command such as "trial one starts" "trial one stops" and etc. without knowing which amp the person in the "amp room" is switching on.
Then you would have a Double Blind test, which is much more reliable than your procedure.
To perfect this experiment, all you need is 500 more subjects for audition, and you will have a non-refutable result.

 
Your suggestion is still flawed on several levels when it comes to perceptivity / acuity.  You also need to find three people like you said, and have them dedicate time to a test they may not be interested in.
 
In my example you only need 1 person and can conduct it yourself in your own time, you can control the switch and the switching interval which is important, which your example overlooks.
 
Either way, I never said I'm interested in proving AD797 or OPA627 sound better than conventional op-amps (which are sometimes quoted as completely transparent to human hearing - as long as the circuit is OK), I said I want to blind evaluate.
 
If I can find / invent a testing scenario, then someone else can replicate it and compile significant statistics of chance via their listening if they want.  A second person can install the op-amps into the multi-channel amplifier by rolling a dice.
 
Jun 3, 2012 at 7:02 PM Post #10 of 12

kiteki

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Instead of looking for multichannel amps, how about just two different amps?  You can use the "blind" installation still.  Yeah, maybe CMoys with unity gain stable op amps and low gain, maybe even 1x.  For a CMoy, there are a lot of people who know what works, and a lot of opinions on what is better, so there's some knowledge base / mythology to work with.
 
One problem with blind installation is that you still need to put the op amps in the correct way.  Hopefully they all have the notch in the same place.

 
I accounted for that, they'll all look identical and have the notch in the same place.
 
I don't really feel like buying three or four identical cMoy's, however that would work with the blind install.  Any other amplifier ideas?  It would be interesting to compare a 9V cMoy with an 18V cMoy both using something like the OPA627 however, and not knowing which is which!
 
 
So which op amps would you be wanting to test? Are you talking about op amps to drive headphones directly, or in another part of the circuit?

 
To drive headphones / IEM's directly.  I'd like to test AD797, OPA627, OPA111, NE5532 and various others which I'll purchase.  I'll drive the amplifier from my DAC using LT1128 or something.  I don't want any buffers or colourful capacitors involved just as short a link to the source as possible.
 
Jun 6, 2012 at 7:48 AM Post #11 of 12

kiteki

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Jun 6, 2012 at 11:26 PM Post #12 of 12

kiteki

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Well I found a way to blind evaluate speakers or speaker cables but this isn't really helping my case is it...
 
http://www.ebay.com/itm/8-Zone-Premium-Speaker-Distribution-Controller-System-With-Headphone-Output-/350516469305
 
SPSW-8P-Diagram.gif

 
 

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