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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: Re: Living Under a Rock, or a Troll? posted by TomLarson on February 7, 2007 at 20:05:36:
An ADC and a DAC have very specific and defined jobs, the measurements, as lame and inadequate as they still are, are dialed in to test them for those attributes they are believed to require to perform their jobs well, etc.A digital EQ on the other hand, is deliberately changing the bits, and I can assure you, it is NOT just the EQ of the amplitude that is going on. Unfortunately, the measurements we are currently limited to DO NOT truly test the digital EQ's properly for all that they are doing to the signals.
Various algorithms must be used to create these digital filters, and while most of these algorithms are designed to EMULATE an analog circuit and it's amplitude response, they ALL introduce other problems during the signal manipulations to achieve the intended changes in the amplitude response.
All of a sudden, all kinds of subtle and bizarre things rear their ugly heads to sully the signal: digital multipication, addition, subtraction, dithering, truncation, buffering, and so on, not to even enter into the extremely difficult realm of which algorithm to use.
Many digital EQ's use a form of the digital bi-quad algorithm, which is KNOWN to be suboptimal, but it is what the "free" software that the DSP or the digital filter chip they used came with, and 9 times out of ten, they use the default programming, the default software and algorithm, etc., you end up with the cheapest digital filter solution on the market. Guess what, it don't sound so hot.
Some companies, such as Apogee, Wadia, Arcam, etc. create their own digital filter algorithms, as do some of the digital EQ folks, such as Lake, and some of the others. Are these the ultimate? Who knows, but at least they tried to go one better than the default freebie software the hardware came with for bare minimal functionality. Someone actually listened to those algorithms to see if they sounded better than the cheapie defaults, and in most cases, they do sound much better. Are they perfect? Probably not yet.
Does YOUR particular digital EQ have custom algorithms that were carefully researched and listened to and tweaked by ear, or are they the "out-of-the-box" algorithms that came with the chip-set?
Who knows?
For instance, Behringer tends to "borrow" other companies algorithms, but they don't always pick the 'good ones', since they are limited to who else is using that particular chipset and general hardware. Most of what I have heard from the Behringer stuff is pretty much mid-fi quality, not that good.In theory, routing the signal chain as you desribe CAN provide the potential for a much better situation, but ONLY if the digital EQ is really up to par, which right now, means a near SOTA unit with totaly custom and tweaked algorithms, and these aren't readily available for less than about $4-5k or so.
Good luck!
Jon Risch
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Follow Ups
- Serious answer - Jon Risch 17:16:58 02/16/07 (1)
- Re: Serious answer - TomLarson 16:29:33 02/18/07 (0)
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