How do you reliably ABX equipment that needs to be disconnected, and how can TOS #8 be satisfied in such situations? Options

[BearcatSandor]

(I was not sure where to put this. My emphasis is really on the testing methodology, not TOS #8 so i decided this would be the best area to put it in)

I'm still new here and trying to learn about proper ABXing and how to avoid the threat of a dreaded TOS 8 hammer (unsuccessfully it seems). I was asked about whether i had done an ABX test between 2 amplifiers. That got me thinking about how one would be able to do that in the first place in their own home.

Suppose i am ABXing a similar amplifier against the one i already have. My system is: Sound card ---> interconnects ---> amplifier (2 channel/1 input) ---> speaker cable ----> speakers
New amp would be the same: Soundcard ---> interconnects ---> amplifier (2 channel/1 input) ---> speaker cable ----> speakers
(a third one is needed? How does that work with hardware?)

To switch between the amps my assistant would need to move the interconnects back and forth between amps and the sound card outputs. That involves making sure that the amp 1 is shut down, removing the cables from amp 1 and plugging them into amp 2 and turning on amp 2. There would be significant lag in doing so, wouldn't there? The same problem would be there for cable ABXing as well.

Doesn't lag play a part in the accuracy of these tests?

How do you folks satisfy an ABX request in such a situation? Do you commonly have some sort of switching device in your home? How would i provide a sample for the community as outlined in TOS #8 (making it unsatisfiable)? Provide duplicates of the system used?

I looked around the site for information on how to ABX components but what i found seemed to relate to sound files and not hardware.

Could you folks help me understand this?

Thanks

[Arnold B. Kruege...]

(I was not sure where to put this. My emphasis is really on the testing methodology, not TOS #8 so i decided this would be the best area to put it in)

I'm still new here and trying to learn about proper ABXing and how to avoid the threat of a dreaded TOS 8 hammer (unsuccessfully it seems). I was asked about whether i had done an ABX test between 2 amplifiers. That got me thinking about how one would be able to do that in the first place in their own home.

Suppose i am ABXing a similar amplifier against the one i already have. My system is: Sound card ---> interconnects ---> amplifier (2 channel/1 input) ---> speaker cable ----> speakers
New amp would be the same: Soundcard ---> interconnects ---> amplifier (2 channel/1 input) ---> speaker cable ----> speakers
(a third one is needed? How does that work with hardware?)

To switch between the amps my assistant would need to move the interconnects back and forth between amps and the sound card outputs. That involves making sure that the amp 1 is shut down, removing the cables from amp 1 and plugging them into amp 2 and turning on amp 2. There would be significant lag in doing so, wouldn't there? The same problem would be there for cable ABXing as well.

Doesn't lag play a part in the accuracy of these tests?

All good points.

ABX evolved in a time (1970s) and place (a bunch of experienced audio techs) where people had a lot of technical resources that are probably a lot less common today.

For example, the first pre-ABX amplifier tests were done using a remote-controlled amplifier/speaker switch box that was operated by someone who had a clear view of everything. This solved the cable-swapping problem. The first amplifiers that were compared were power amps that had input level controls, so level-matching was a slam dunk.

The first refinement was developing a blinded randomizing controller that operated the remote controlled amplifier/speaker switch box. Once we got the basic ABX procedure working, we incorporated speaker-level switching into the randomizer. When we moved on to comparing line-level items like LP playback, we devised matched preamplifier's that had switching relays built-in. They were slaved to the speaker-level switching in the ABX Comparator. When we moved to CD players, we built a dedicated line-level swticher that was also slaved.

When we started comparing equipment that lacked appropriate built-in volume controls, we developed external volume controls with fine adjustments.

In most cases the "we" was "I". ;-)

How do you folks satisfy an ABX request in such a situation? Do you commonly have some sort of switching device in your home? How would i provide a sample for the community as outlined in TOS #8 (making it unsatisfiable)? Provide duplicates of the system used?

I looked around the site for information on how to ABX components but what i found seemed to relate to sound files and not hardware.

Could you folks help me understand this?

Eventually a purpose-engineered system for hardware ABX was developed. a partnership of 6 people (still friends to this day) was formed to develop, produce, and sell it. You can find out more about it here:

ABX Comparator Hardware Web Site

This hardware was sold to a number of equipment and R&D shops over a period of maybe 5 years back in the 1980s. More than 50 systems were sold. There are no central records of who currently owns them or how operational they are.

In the mid-1990s ABX and similar or improved blind listening tests became very interesting to people who developed perceptual coders. This kind of testing is well-served by file comparison software.

In the year 1000 a methodology I called PC ABX was developed and popularized via a web site called www.pcabx.com. It was based on playing files on a computer using purpose-written software.

The files being compared can be produced by recording the outputs of audio equipment. ADC and DAC technology has progressed to the point where the best ADCs and DACs are comparable or superior to most audio equipment,. Using them to record and play the output of audio gear does not significantly degrade sound quality.

[pbelkner]

Using them to record and play the output of audio gear does not significantly degrade sound quality.

How do you ABX this one?

This post has been edited by pbelkner: Nov 2 2010, 14:32