As it RC - passive bell EQ - Q can be calculated from the following-
Freq:
Low - 20-100Hz,
Low Mid - 100hz-1Khz,
High Mid - 1-8Khz,
Hi-8-20Khz,
and depth of adjustment - Low and Hi - +/-3 dB, Low Mid/High Mid - +/-6 dB.
Adjustment occurs by 21 pattern switches on each band (ceramic military switches).
Probably, depth of adjustment will seem to someone insufficient - but it would be desirable to notice, that the more depth of adjustment - the more than phase distortions. Usually it try to compensate a feedback - but we do not use feedbacks, the whole, in all our devices - as the doubtful decision for hi-end.
Certainly, the feedback allows to have limits down to +/-20dB - but we do not see in it any sense, also owing to the big phase distortions in a result - that deprives with sense an invention).
Thus - we have passive bell RC EQ - and and all cascades in full A class, without a feedback. And main switch for it all - Bypass
