Brunswick 'Light Ray' Records

[Viva-Tonal]

Fantastic data regarding the amplifiers Brunswick used! Is there a date and matrix or issue numbers wherein the change was made to the better equipment with the condenser mike? It would be later on in 1926, certainly before 8 December 1926 and the Red Nichols sides on 3407 ('Washboard blues' and 'That's no bargain') recorded with the newer system.