Most DACs are designed to be as flat as possible and do not include EQ or tone adjustments.
There are two reasons for this:
First off, most folks consider a DAC to be a source component, like a CD player, and expect it to simply deliver the signal as accurately as possible.
Alterations and adjustments are left to other components - like preamps and processors - and so would be "inappropriate" in a DAC.
Second, most high performance DAC chips don't include this functionality.
Therefore, adding the ability to alter the signal would require the addition of a lot more circuitry, none of which would enable the DAC to perform its basic functionality any better.
There is also the perception that "a good DAC should deliver an accurate signal without messing with it".
(Many lower-performance "all-in-one" DAC chips, of the sort used in low-cost equipment, do include this functionality.)
There are some exceptions.
A few modern "DACs" are really a combination DAC and digital processor, and do offer tone controls (I believe the $500 Monoprice DAC has some "adjustments" although I'm not sure which ones).
Some "audiophile DACs" introduce various sorts of coloration to the sound (although they frequently don't admit that's what it is).
For example, in many implementations, Sabre DAC chips add their own sonic signature, which makes many products that feature them sound somewhat brighter.
Some DACs even feature tube output stages, or other unusual bits of circuitry, which serve no purpose except to add coloration to the sound (as a product differentiator).
There are a huge variety of different ways in which frequency response can be altered...
(There are also a huge number of ways in which sound can be altered beyond simple EQ.)
In general, a properly designed software control should introduce very little unwanted coloration, beyond what you set it to, unless deliberately designed to do so.
(Filters and adjustments implemented in software should be "theoretically perfect" because they avoid issues like component inaccuracies and unexpected distortions due to circuit limitations.)
(Some software controls are simply badly designed; in others coloration is intentional and is considered to be "part of the effect".)
Foobar2000 is an excellent (and free) software music player.
It is very flat, but there are a huge number of plugins available for it, many of which offer various sorts of EQ and tone control, among other things.
Programs like jRiver Media Center also offer lots of options.
okay good, its not just me! I will use a software EQ to see what I can do but i usually find they muddy the sound up. Are all DAC's normally flat EQ? or does it vary by manufacturer?
