READER REPLIES: Analog vs digital EQ

Here is where you, our readers, can comment on matters of mutual interest.

A1: During the 1970ies analog equaliziers came into the hifi land. Beside the level adjustment per frequency span also parametric ones appeared where a center frequency of on of the filters could be tuned. Trying all this, I was never really happy with the sonic result. Maybe because at that time we did not measure the frequency response with microphones. DSP equalizers seem to be perfect regarding the math behind it and filters can be made which are not always possible in analog design. Since I am not in the recording business I feel that I don’t need equalizers for my system.

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A2: I often wonder if hardcore audiophiles are stuck in the last century of audio technology when there was a firm belief that only analog master tapes and vacuum tube based amp stages could offer the best sound quality – the shortest signal path realized, of course. Having the chance to play around now for more than two decades with a digital amp (only digital inputs) from Tact Audio (see: ) and all kind of digital signal processing devices (including Roon Nucleus+) for correcting unwanted effects (room acoustics, inherent crosstalk and phase error in passive loudspeaker designs) I never would go back to the theoretical idea of “shortest signal path”. And hasn’t Paul McGowan recently announce to launch audio components with SMPSs? 🙂 In the realm of medicine researchers told me that it takes at least 15 to 20 years for a new (evidence based in research) therapy to became a therapy commonly applied. Maybe it takes 50 years in the realm of audiophiles to accept new and groundbreaking technologies?



t is hard to alter the mind of people, whatever theme it is. On the other hand, like me for instance, I love old technical gear which was well built to last forever. This also because I was working half of my life for Hewlett Packard where the instruments were built with extra quality, such as gold plated printed circuit traces. No more nowadays of course.
And we have a few classic Chevrolet cars with V8 350 cui motors. It is just FUN. So I can understand that audiophiles still like the vinyl discs where the stored music is visible under a microscope thus having the real waveforms. In digital all is hidden and one has to believe that the music is in it.



I believe it is very important to know what you are actually doing when using EQ. That means, you should be able to measure the resulting frequency response at your listening place. One example of an equalizer able to do that is the Accuphase DG-68, which is able to show the current frequency response and correct the signal to achieve a frequency response determined by the listener. However, there are different opinions as to how that ore similar devices should be used. Some believe these devices can be used to compensate the deficiencies of mediocre listening rooms. I strongly disagree with that. Listening rooms should be optimized by acoustic means (in a controlled manner, tailored to the respective room) as far as possible under the given circumstances. Then equalizing should be used only for the final fine-tuning which was not achievable, or not achievable at reasonable costs, with acoustic measures. Also in a typical home listening situation, e.g. in a living room, an EQ may have another purpose than correcting the overall frequency response. The latter may be achieved by the above-mentioned acoustic measures. However, a typical home room is hardly going to be symmetric. So, any resulting differences in frequency response between the L and R speakers could be corrected by an EQ. Furthermore, it should not be forgotten that an EQ can correct only one aspect of correct sound reproduction, namely the frequency response. Regarding speakers, an EQ may better the reproduction of a speaker having deficiencies regarding its frequency response but it cannot correct the phase problems of a poorly designed multiple driver speaker. With regard to the listening room, it depends on the reason for the respective deficiencies in the frequency response at the listening place, whether they can be correct by an EQ or not. If e.g. there is comb-filtering because of phase shift between the direct signal and a reflection thereof, the EQ can do nothing: If the output at the problematic frequency is lowered or increased, this will affect the direct sound AND the reflection and the undesired cancelation or enforcement of the particular frequency will remain. So, this problem can only be dealt with by controlling reflections by acoustic means. The same holds true for deficiencies in stereo reproduction due to reflections. In conclusion for me EQ may make sense, but only for some very clearly defined and limited factors of acoustic reproduction.

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