10.
Calibrating the
electro-music
Klee Sequencer
Calibration Notes
You’ve now had plenty of opportunity to scrutinize the Analogue Board and become
intimidated by the fact that it seems to bristle with trim pots. Really, there’s nothing to
fear here, and we’re not saying this in the voice your doctor reserves for something you
really
do
have to fear.
There are ten trim pots (nine if you’ve installed one of the variable range options). Two
of the trim pots are used to zero the offset of the op amps that sum the Register A
voltages (stages 1 through 8) and the Register B voltages (stages 9 through 16).
The remaining trim pots are used to “dial in” the maximum range voltages of the
programming pots. There is a trim pot for each position of the Range Switch, hence the
intimidating number of trim pots.
This procedure will address the “standard” voltage arrangement reflected in the
schematic. If you decide you would like different voltages for the various positions of
the Range Switch, check out the Analogue Board section of Chapter 7.
Required Tools
A digital volt meter (DVM) is the only piece of test equipment required for the
calibration. Of course you’ll need a trim pot adjustment tool (tweaker) as well.
The Offset Zero Calibration
The zero calibration helps to eliminate excessive DC offset on the voltage outputs of the
electro-music
Klee Sequencer. It does not totally eliminate offsets – there will be some
minimal offset on each of these outputs even after this calibration, due to the mixing
stages after this section, so don’t let that worry you as to whether you’ve calibrated this
section correctly.
Another reason the zero calibration was put in here is that, once the offsets are zeroed,
it’s easier to calibrate the range voltages.
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