UPDATE: This question has been solved. I updated the tutorial files with the solution.

You can solve this by plotting your own sinewave in an array with the sinesum function with enough size to calculate low frequencies, for example: an array with 65536 points.
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Hello pd people,
I’m triggering a biquad bandpass filter with one milisecond pulse to create a faithful TR-808 bass drum emulation.
(Source: http://www.dafx14.fau.de/…/dafx14_kurt_james_werner_a_physi…)

Since I will compile it with heavy hvcc, expr~ is not supported, and I had to use [cos~] instead of [expr~ cos($v1)] for calculating omega at audio rate.

This created a notable pitch difference when setting the filter cutoff at low frequencies. The filter using expr~ achieved the set fq 50 Hz, but the one using [cos~] plays 65 Hz instead.

Does anyone know the reason/solution to this issue?
Thanks.