9730 Dual VCF w/Modulator Sound Tests

This page is supplemental material to the 9730 Assembly and Using manual.

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Voltage Controlled Filter 9730 - Test 4 & 5

Test 4

These tests verify the operation of the two filter sections independently.  The four tones in the sample are 1) Square Wave Input 2) Hi-Pass 3) Band-Pass and 4) Lo-Pass.  All tones were recorded at the same input level and the difference in volume is the normal result of the harmonic structure of the square wave.  For example, Lo-Pass is very soft because most of the harmonics of the input sqare wave are higher than the Corner Frequency and are consequently attenuated.  The Hi-Pass ouput is relatively strong because the higher harmonics are passed without attenuation.  Fc in this example is about 128 Hz. — the four octave total range of the Freq control above the 16 Hz. “0V CV” frequency.

Test 5

Checks the operation of the modulator, first with Q set as shown above and then with Q control manually advanced from min to max while sweeping Fc with the modulator.

Voltage Controlled Filter 9730 - Test 6

Test 6

Verifies that the normal patch of filter A LP output to filter B Input is intact.  With Fc of the two filters offset from one another both resonant peaks can be heard.

Voltage Controlled Filter 9730 - Test 7

Test 7

Verifies normalized patch from Fc2A to Fc2B.  Early version of the manual stated that this increases the range of the modulator from 5 octaves to 10 octaves, but in fact with Output Control max’ed, as in this sample, the filter is sweeping 15 octaves.