Lithium Grim ColoredThro, Инструкция по сборке

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ColoredThro v1.0
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11
Biasing
The transistors Q1 , Q2 and Q4 need to be biased. The best way to do this is by using the biaspots
VR1-VR3 .
The Colorsounds did not come with bias pots, but had fixed resistors. These values are mentioned in
the table below. If you prefer you can place resistors instead of the trimpots. If so, omit the trimpots
and instead connect the fixed resistors with the correct value mentioned below to the pads marked
1
and 2 of VR1-VR3 .
However, I recommend that you use the trimpots. Every transistor is different and may or may not
sound optimal with the given values. Start by setting the trimpots to the values mentioned in the
table (preferably before soldering them to the pcb). To measure the resistance correct use an digital
multi meter and measure the resistance between pins marked
1 and 2 . For your convenience I
marked these pins also on the backside of the PCB. After setting the pots, test the effect. If it does
not meet your expectations you can measure the voltage per transistor. I marked the collector pads
of each transistor on the backside of the PCB. Use the red probe on these pads and the black probe
to ground to get a good reading. Adjust the corresponding trimpot to get to the target voltage. If
both techniques do not give you your optimal sound then find your own sweet spot.
Colorsound Throbak Target voltage
Biaspots Transistor Power boost Overdriver Overdrive Boost @9V @18V
VR1
Q1
4k7 6k8 5k6 2.5V 5V
VR2
Q2
1k8 1k8 2k 5V 10V
VR3
Q4
3k9 1k8 1k5 6.5V 13V
Note that turning VR1 does not really influence the collector voltage of Q1 as it is connected to the
emitter.