Thanks, George. But actually it isn’t that bad. Note the presence of the 100K output level control. The cap will only "see" the input impedance of the power amp when the 100K output level control is at or near max. (Actually in that case it would see a heavier load than that input impedance since it would be paralleled with the 100K). And my suspicion is that under typical conditions the control would be set closer to the bottom of its range than to the top of its range.
So the resistance that forms a high pass filter in conjunction with the 0.1 uf would probably be comprised of the majority of the 100K, plus the parallel combination of the rest of the 100K and the input impedance of the amp. And if the control is used near the bottom of its range, that would amount to close to 100K overall.
Nevertheless, assuming the schematic reflects the present design, per some calculations I did prior to my earlier posts there would be upwards of 2 db of rolloff at 20 Hz even with no power amp connected and regardless of the setting of the control. Which already considerably exceeds the +/- 0.7 db tolerance of the 20 Hz to 20 kHz frequency response spec. There would also be phase shifts in the bottom octave that could very well be audibly significant. With the rolloff and the phase shifts especially likely to be problematical in a case like the OP’s, involving large speakers having excellent deep bass extension, and also for others who may be using subwoofers. (Compensating for the rolloff with the level control of a subwoofer would be a crude approximation at best, since both the amount of rolloff and the corresponding phase shift would vary as a function of frequency).
Best regards,
-- Al
So the resistance that forms a high pass filter in conjunction with the 0.1 uf would probably be comprised of the majority of the 100K, plus the parallel combination of the rest of the 100K and the input impedance of the amp. And if the control is used near the bottom of its range, that would amount to close to 100K overall.
Nevertheless, assuming the schematic reflects the present design, per some calculations I did prior to my earlier posts there would be upwards of 2 db of rolloff at 20 Hz even with no power amp connected and regardless of the setting of the control. Which already considerably exceeds the +/- 0.7 db tolerance of the 20 Hz to 20 kHz frequency response spec. There would also be phase shifts in the bottom octave that could very well be audibly significant. With the rolloff and the phase shifts especially likely to be problematical in a case like the OP’s, involving large speakers having excellent deep bass extension, and also for others who may be using subwoofers. (Compensating for the rolloff with the level control of a subwoofer would be a crude approximation at best, since both the amount of rolloff and the corresponding phase shift would vary as a function of frequency).
Best regards,
-- Al