Audiophiles in the 1970s and 1980s preferred to buy each component separately. That way, they could choose models of each component with the specifications that they desired. In the 1980s, a number of audiophile magazines became available, offering reviews of components and articles on how to choose and test speakers, amplifiers and other components. Listening tests are used by hi-fi manufacturers, audiophile magazines and audio engineering researchers and scientists. If a listening test is done in such a way that the listener who is assessing the sound quality of a component or recording can see the components that are being used for the test (e.g., the same musical piece listened to through a tube power amplifier and a solid-state amplifier), then it is possible that the listener's pre-existing biases towards or against certain components or brands could affect their judgment. To respond to this issue, researchers began to use blind tests, in which listeners cannot see the components being tested. A commonly used variant of this test is the ABX test. A subject is presented with two known samples (sample "A", the reference, and sample "B", an alternative), and one unknown sample "X," for three samples total. "X" is randomly selected from "A" and "B", and the subject identifies "X" as being either "A" or "B". Although there is no way to prove that a certain methodology is transparent, a properly conducted double-blind test can prove that a method is "not" transparent. Blind tests are sometimes used as part of attempts to ascertain whether certain audio components (such as expensive, exotic cables) have any subjectively perceivable effect on sound quality. Data gleaned from these blind tests is not accepted by some audiophile magazines such as "Stereophile" and "The Absolute Sound" in their evaluations of audio equipment. John Atkinson, current editor of "Stereophile", stated that he once purchased a solid-state amplifier, the Quad 405, in 1978 after seeing the results from blind tests, but came to realize months later that "the magic was gone" until he replaced it with a tube amp. Robert Harley of "The Absolute Sound" wrote, in 2008, that: "...blind listening tests fundamentally distort the listening process and are worthless in determining the audibility of a certain phenomenon." Doug Schneider, editor of the online Soundstage network, refuted this position with two editorials in 2009. He stated: "Blind tests are at the core of the decades' worth of research into loudspeaker design done at Canada's National Research Council (NRC).