Tom Fine:

>How does a computer equalizer have 
>an "analog" mode? What am I missing?

There is two types of digital EQ.

1/ Minimum Phase.

2/ Linear Phase.

Minimum Phase EQ behaves exactly as analogue EQ.

That is when increasing or decreasing the amplitude of a certain band of frequencies then there is a corresponding change in the phase response that mimics an analogue EQ in every way.

Linear phase EQ changes the amplitude of the boosted or cut frequencies as the Minimum Phase EQ do but there is zero change in the phase response. So the phase never changes no matter how much boost or cut in amplitude you use.

I would say that around 99 % of digital EQ available is of the Minimum Phase type that exactly mimics analogue EQ as we are used to.

Linear Phase EQ entered the digital world late as it uses much more CPU processing power.

When I updated my Weiss EQ1-DS MK2 EQ to Linear Phase then the whole processor card had to be exchanged because the processor was not up to the task. 

>Also, I thought Gary's article in ARSC J said NO 
>digital equalizer properly de-emphasized RIAA or 
>Columbia curves. 

When I started using the Sonic Solutions SSP2 in 1991 then the EQ section was Minimum Phase and there was a correctly designed Minimum Phase RIAA filter in there too.

I just do not understand if there is a problem as there has never been a problem in the beginning nor now.

I have measured a few of the digital RIAA EQs and they were all Minimum Phase EQ.

So my own measurements do not agree with the conclusions of the article in ARSC J.

>That's why I asked what digital EQ 
>people were using nowadays.

I have about 15 different digital EQ´s and they are all sounding slightly different because of the different shortcomings in their design.

Just as Analogue EQs sound different depending on the shortcoming here too.

Nothing new you just have to find something you like.

Best regards,

Goran Finnberg
The Mastering Room AB

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