Appendix A - Calibration - Abstrakt Instruments Avalon Reference Manual

APPENDIX A - CALIBRATION

1 VCO CALIBRATION
The oscillator can be calibrated through the two holes in the bottom of the unit. There are numerous ways to perform calibration, one method
follows:
1 Set TUNE to center position.
2 Place the synth into PATTERN WRITE MODE.
3 Using a frequency counter or tuner, monitor the SAW OUTPUT from the 1/8" jack on the rear of the unit.
4 Select a pattern, clear it, and program one long note by pressing and holding STEP BUTTON 1 + STEP BUTTON 16.
5 Press and hold STEP BUTTON 1 and select C2 for the pitch (the lower C on the keyboard). Verify there is no transpose setting.
6 Select a second pattern, clear it, and program one long note by pressing and holding STEP BUTTON 1 + STEP BUTTON 16.
7 Press and hold STEP BUTTON 1 and select C3 for the pitch (the higher C' on the keyboard). To avoid confusion please note that in accordance
w/ TB-303 operation a high C' note will display as a low C note with UP transpose if selected again for viewing.
8 Monitor the SQUARE OUTPUT for audible feedback by plugging it into your mixer or interface.
9 Press RUN on the sequencer and select the first pattern (C2) programmed in steps 5 & 6 above. The tempo is not critical as we're monitoring the
direct saw and square outputs before the filter and final amplifier.
10 Adjust the TUNE trimmer until the frequency is close to 65.4Hz.
11 Next, play the second pattern (C3) programmed in steps 7 & 8 and adjust the SCALE trimmer for approx. 130.8Hz. This is exactly one octave
above the previous step as the goal is to adjust the C to C' scale as exactly one octave.
12 When the trimmer in step 11 is adjusted it changes the base C2 frequency in step 10 so steps 10 & 11 will need to be repeated several times
until the frequency and scale is dialed in. .
Use only the included trimmer tool or equivalent or the trimmers will likely be damaged. Suitable replacements are Bourns Part # H-90 or Vishay Part #
ACCTRITOB308. These are available from your electronics supplier or from our online store.
2 INTERNAL FILTER ADJUSTMENTS
These adjustments should only be performed by a qualified technician.
There are (3) internal adjustments relating to the filter. These adjustments allow the filter controls to retain the same behavior as the TB-303
controls or to allow an extended range. To access these switches the bottom cover of the synth needs to be removed. To remove it unscrew the (6)
M3 metric screws. A Phillips #2 JIS (Japanese industrial standard) screwdriver should be used.
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AVALON - Reference Manual