OldGuy said:
Does Win 7 Pro have audio tone control? I searched thru the Win 7 menus
etc.
I am running my laptop HDMI out through a Lenovo Monitor that has an
audio output to my speakers. Monitor on laptop is off so only the
Lenovo monitor is on.
The Lenovo shows up in the Win 7 audio controls and I get stereo sound
out of the speakers plugged into the Lenovo but the tone is off for me.
I want more treble or less bass.
Can this be done?
Tone control happen three ways:
1) Some sound cards, had bass and treble controls in hardware.
This was probably some kind of analog scheme, as it predates
the usage of DSP. DSP (digital techniques) came later.
In some cases, the interface controls had a position for
the knobs or sliders, but they were greyed out. And that
told you, that the hardware didn't have the effects present.
I don't think any of my crap cards, had this working. My
sliders were always "stuck".
http://i46.tinypic.com/etip8i.jpg
They just don't do that any more. It's "EQ or nothing" now.
2) Modern AC97 or HDAudio, don't normally have such things.
Instead, the audio drivers have DSP filters which give a
graphic equalizer interface. In some cases, this remains
hidden, until you turn it on in the prefs. My current
machine, looks similar to this one (my EQ is turned off
right now, don't need it). With my previous stereo, I used
this approach a bit, for better ambience. But that stereo
blew, and the current solution needs no EQ.
http://i35.photobucket.com/albums/d186/jennymanda/soundmax.jpg
We'll pretend that used 100 to 200MHz of your CPU (i.e. a
little bit of overhead). The CPU executes digital signal
processing code, that processes the sound bytes headed for
the stream interface on the hardware. So the digital samples
are filtered, as you desire, before they get to the hardware.
And the driver does that. In a way, virtually any sound card
company could do that for you. Or, you could search for a
third party package to do it. (Don't know of any off hand.)
The function is not so special, that the techniques aren't
well known. Don't know what the patents are like though.
Any calculation of that type, adds "latency" to the audio
path. I don't know what that number is. But it could
affect lip sync, or game effects.
3) At least one motherboard, the Southbridge had five DSP engines.
And at least one of those, supported the graphic equalizer
function. That means, you get the interface in (2), but with
no load on the main CPU at all. The Southbridge did all the
calculations. I have one of those
It could also do AC3
encoding on the fly (which I couldn't use).
So start looking for that "EQ stuff". Try under your sofa cushions...
4) They also makes chips for this. Crude example here.
This could be the basis for a home project, with some soldering
required
This would be the approach some of the first EQ
implementations would use. It's pure analog, and is like a
deluxe version of (1). For the squiggly potentiometer symbols
along the bottom of the diagram, you buy the slider variety.
My sample slider, costs $0.73 each. So five bands times stereo,
would cost $7.30 for the sliders.
http://www.electronic-circuits-diagrams.com/audioimages/12.gif
http://www.bourns.com/data/global/pdfs/PTA.pdf
HTH,
Paul
