Hi all! Whilst we're working on the detailed design (& possible remote computerised control) of our ABX switch box, I thought I'd put down my ideas so far on the practical aspects of the DBT.
These are the Rules Of Engagement: 1. Level matching to 0.1dB or better for each balanced input of the switch box will be set using a dual mono 1kHz sinusoidal test tone by means of trimmers *-inside-* the box which should not need to be opened during the test in case the cat gets out. Panel members will be able to verify that this has been done correctly by observing measurements taken from the output of the switch box. There is obviously no separate input for "X", but the fact that the switch box is functioning correctly (i.e. adhering to the same level settings when switched to "X") may also be checked, together with the "A" & "B" signal levels, at any time during the test on request by a panel member in the same manner. This level-matching will be checked again the same way mid-way through & at the end in any event. 2. I shall preselect a selection of well-recorded & diverse programme material from my eclectic selection of 6,500 albums (say 20 tracks) designed to cover a wide range of genres, AAD/ADD/DDD material, and lossless formats (16/44.1; 24/44.1 or 24/48; and 24/96 or 24/192). Obviously any 24/192 will be transcoded to 24/96 by LMS before onward transmission to my Transporter. Participants will also be encouraged to bring a *-small-* number of tracks of their own lossless material, which I shall be pleased to include at this preliminary stage for the listening panel as a whole to consider whilst the final shorter list is being determined (see Rule 3). 3. All of this programme material will be used for an initial acclimatisation phase of the test. Any specific tracks which are not to the musical taste of members of the listening panel can be identified & eliminated at this stage, although the requirement for a variety of genres, recording methods & formats will remain paramount. So anyone who only likes Country & Western will be in for a rough time. I would hope that we will be able to retain around 10 individual tracks for the actual test as a result of the listening panel's expressed preferences. My adjudicator's decision on the final selection will however be binding if the panel are unable to agree on the selection themselves. 4. There is no rule 4. 5. The acclimatisation period will be of fixed duration, say 90 minutes. If any panel members are unable to detect -*any*- differences between the known sources "A" & "B" after this time, they will be given a further 30 minutes of acclimatisation during which they can call the programme material from our final selection of 10 tracks, either jointly or severally (in the event that this pertains to more than 1 panel member). If they are *-still-* unable to distinguish the known sources, they will be assigned alternative roles (operator, scrutineer, or chief tea-maker - there are separate rules for that btw :cool: , or even gofer) because their further participation in the test would be pointless - they could only make blind guesses. Panel members will be encouraged to describe the subjective differences they think that can detect between "A" & "B" in best "Stereophile" tradition as colourfully as their erudition will permit (because we're all curious) & which source they prefer from a musical standpoint. These comments will be reported along with their subsequent relative success (or failure) rate over the course of the objective test to identify "X" under double-blind conditions, although I promise to do this anonymously. More to come, & I may need to edit this because I'm formalising my ideas as I type it. I don't want to bust the word count. Dave (cheerful, but emoticons have packed up - strange) ------------------------------------------------------------------------ Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106519 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
