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SERVICE BULLETIN
Preamp Tube Replacement
Products Affected: xs400, xs400t, xs400h, xs800h, the
DynaBass Series (the 400, 400t, 400h and 800h).
In order to maintain consistent audio sound quality and performance replace
preamplifier tubes in the xs400, xs400t, xs400h, xs800h, the DynaBass Series
(400, 400t, 400h and 800h) with Yorkville specified and sorted 12AX7 tubes
(Yorkville Sound part number "12AX7SORTED").
The specified tubes are chosen for their combined attributes of low noise,
high gain and no microphonic feedback. The following chart demonstrates a
sampling of 1000 tubes tested and the percentage deemed acceptable.
Distribution of 12AX7 Gain Measurement [N = 1000]
Tubes used in the DynaBass 400, 800H, XS400 and XS800H
are extracted from the upper quartile of the tube population
Canada
Voice: (905) 837-8481
Fax: (905) 837-8746
w w w . y o r k v i l l e . c o m
Yorkville Sound
550 Granite Court
Pickering, Ontario
L1W-3Y8 CANADA
1
U.S.A.
Voice: (716) 297-2920
Fax: (716) 297-3689
Yorkville Sound Inc.
4625 Witmer Industrial Estate
Niagara Falls, New York
14305 USA
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