I'd like to alter the filter frequencies and expect that changing the clock frequency R and C at pin 8 would do that. Does anyone know where to find better info on the MSGEQ7 EQ chip than its standard datasheet which is very basic, but does imply there's a range for the clock frequency...
Clock Frequency FCLK, C = 33 pF, R = 200 kohms, 145, 165, 180 kHz
Would expect that to lower the filter frequencies by say 20%, could lower the clock by 20%. From the spec'd center freq of 165 kHz, that'd be 132 kHz, still inside the spec range.
THink that'll work and any other tricks for this device?
I called MSI today and asked about the ability to change the filter frequencies by changing the clock frequency and it can be done!
Nominal clock freq is 165kHz using 33pF (C) and 200kOhm (R) at pin 8, with MSGEQ7 tolerance of 145kHz to 180kHz (+/- 12% from 165kHz).
MSGEQ7s from the same lot are close to being all the same. Tolerance is for lot-to-lot variation.
On low side, freq can be dropped to 1/10 (yielding 6.3Hz, 16Hz…) and on upper side, maybe 2x (126Hz, 320Hz...).
Can use CMOS external clock to pin 8 in place of the RC.
Minimum "sample" rate from 63Hz output to 63Hz output is 7 * 72us (tss Strobe to Strobe) or 504us.
MSGEQ7 was released in 1997 for graphical display on boom boxes!
Thank you very much for the info! it's crazy this is not on the datasheet