TAS5805M: Post EQ for audio processing

Hi Mark,

can you elaborate on the specific situation？

The post EQ only applies in individual mode.

And can you explain how you use EQ for an additional HP filter in detail?

You can give me some PPC3 or I2C configuration.

see the attached PPC file. It's a hypothetical setup. The concept is to apply huge amounts of gain for the bass boost. But as the system level is increased, the "HP" effect of the EQ and boost begins to disappear as the output saturates with the set thresholds.

So the concept is to place a HP filter after the DRC in order to create a ceiling of the maximum voltage v frequency.

Below is some measurements to review. The PPC has two snaps shots for each of the measurement states

Hi,

You forget to give PPC file?

And is the red circle part suppressed by your post EQ?

I dragged the PPC3 file into the text and I thought it was uploaded; also was not successful inserting the file. Looks like I may have trouble in my browser, so the wetransfer link below is for the ppc file:

https://we.tl/t-mEhjEB7tNu

The red circle is suppression due to the post EQ. An example of what is desired.

Hi Mark,

I can't open public file sharing in company.

Can you share it with me in the reply?

The only way I guess to send file on this chat is to repackage it. extension ppc3 was always rejected, but looks like .zip is "oK" Example_Post EQ.zip

I comprehend the at "signals are weakened" - that is the point of a HP filter. I comprehend there may be bigger SNR at very low input voltages. The concern was the larger than expected THD+N and a noise gate effect.

At the measured high input levels -12~0dBFS there is significant distortions introduced by the filter. It appears that it is not only attenuating the already compressed signal. Just view the level sweep at 40Hz, take -6dB input as an example: 10Vrms @ 5% vs 3Vrms @ 15% THD+N

Is this expected behavior of post DRC EQ?

Perhaps to illustrate the behavior more clearly, attached is the result of all processing turned off. I only include a HP filter at 60Hz using the amp Post EQ block vs the normal EQ block. There is no gain to cause clipping and the DRC/AGL is turned off. There is clearly a huge contrast in the behavior of the HP filters.

Example_Post EQ (2).zip

Hi Mark,

I understand what you mean.

When the filter center frequency decreases or Q of post EQ filter increases, the truncation quantization error will increase.

So we don't recommend you use post EQ for HP filter at low frequencies.

thanks for your response, so back to my original question:

What are the limitations of Post EQ? 
What is the difference between regular EQ and post EQ?