last update: 18.Jan.201703 March 2017 for 4072 Filtercard, big thanks to Anthony A Flagg
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works best with Scope and good DMM (4,5digits with less than 1% tolerance) |
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Purity adjust ( if you don`t get a SIN, give more gain/voltage, if you haven´t tested with a transistortester your 2N3958 - should be defect)
01) Adjust PURITY for best sine waveform
It might b e necessary to readjust calibrations after performed in the order listed.
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VCF with 4012 VCF (original TTSH)
Frequency calibrate
01) Monitor VCF output with an oscilloscope or frequency couter
02) Initial frequency slider – left
03) Fine tune slider – mid range
04) Resonance slider – right
05) All VCF inputs sliders – down
06) Disconnect or use dummy plug for KYBD CV in
07) Adjust FREQ CALIBRATE for 10Hz output
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Gain adjust
01) Open VCF initial frequency slider – right
02) Resonance slider – left
03) Raise VCO1 input slider and adjust GAIN for same amplitude as measure at VCO1 output
VCF 4072
The only calibration adjustment that seems to make any difference with the 4072 filter module is Initial Frequency. When you remove the 4012 filter and install the 4072 filter, the Initial Frequency is shifted way down, so that the cutoff frequency is at sub audio range somewhere around 75% on the Coarse Frequency control. This one calibration needs to be repeated when changing between filter modules. The 1V/Oct panel trimmer is efficacious with the 4012 filter module, so should be adjusted for that unit, and should be undisturbed when swapping. The Offset and Gain trims work the same for both filters, and should also be undisturbed when changing filters.
The following procedure is written for end-user, and is simplified. Obviously a builder may have a more precise means of measurement.
This is based on the following standards:
a. Note C1 (MIDI note 24) = 32.70Hz
b. 0.00VDC on KBD CV bus produces note C1 at VCO1-3 and VCF cutoff frequency
If you have a different standard, adjust the target frequency you adjust to in step 8 accordingly.
1. Disconnect power and open the case, or unmount the panel if using the standard steel case.
2. Remove the in-use filter module, and install the alternate one.
3. Re-assemble, and power up the instrument. Let it warm up for 20 minutes.
4. Using a midi keyboard and midi to CV device, drive C5 (midi note 72), to produce +4.00V on the KBD CV bus.
5. Adjust the filter’s Coarse Frequency control to minimized, the Fine Frequency control is in the middle, and the Resonance control to maximum.
6. Disconnect any audio and CV inputs, and minimize their controls to the filter.
7. Connect the output of the filter into a guitar tuner. It may help to use the mixer section to attenuate the signal down to guitar level, which is something like .5V p-p (-20dB from the VCF output of 10V p-p).
8. Adjust the Freq. Calibrate trimmer from the front panel in the VCF to get C5/523hZ on the tuner. Getting close is probably good enough here.
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VCA
Linear gain
01) Monitor VCA output with oscilloscope
02) Patch VCO3 saw to VCA ‘VCF Input’ jack and raise audio slider fully
03) Put initial gain slider – left (minimum)
04) Raise VCA AR control slider all way
05) Depress and hold the manual start button and adjust LINEAR GAIN for 10Vpp maximum signal output
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