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- Cosmic Ampworks
5. Assembling a James tonestack and volume control on the back of three potmeters and installing it.
a. Solder a point-to-point James tonestack on the back of two potmeters (Figures 13, 14). First
connect the two pots with R2 (180k); the appropriate distance (i.e. the distance between the
mounting holes in the front of the chassis) can then be set and maintained. The component values
are:
i. Treble pot: 500k (A); Bass pot: 1M (A)
ii. R1 = 100k; R2 = 180k; R3 = 10k
iii. C1 = 330p; C2 = 470p; C3 = 4.7n; C4 = 3.3n
b. Cut two lengths of single-stranded wire of some 7cm each. Connect one side of the one wire to
the junction of R3 and C4 and one side of the other wire to the center lug of the treble pot.
Figure 13. Layout of a James tonestack on the back of two potmeters. Soldering lugs are pointing upwards (as in Figure 14 below).
Out (to
volume
control)
C4 (3.3n)
Figure 14. James tonestack for the GA15 (NOTE: "orange drop" capacitors used here, instead of yellow "mustard" caps). As this is only a 2-
dimensional picture, parts may seem connected that are not; for soldering best rely on Figure 13. Also refer to Figure 15.
© 2020 -
www.cosmicampworks.com
- The Ultimate Harley Benton GA15 Mod Kit- Version 1.4 - 200127
®
Ground (to volume control ground)
R2 (180k)
Treble
(500k (A))
C1 (330p)
13
R3 (10k)
Bass
(1M (A))
C3 (4.7n)
Dedicated to the Advancement of Stellar Tone!
C2 (470p)
R1
(100k)
In (from rear
hole of R58 –
Figure 11)
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