Originally Posted by ENTERPRISE
IM TEH NOOOOOOOOOB.
Thanks spooked. That makes sense now....however what does one have to do for a TRULY digital audio experience ? As you say , the Digital signal is converted back to Anologue !
The true digital Audio experience sounds like high pitched screeching.
Oh noes explanation time
. Here is the in depth definition of my earlier signal flow.
Recorded audio is picked up via a device [microphone] that reacts to the air around it moving. The internal mechanism of the Mic is a diaphragm made up of something that air can easily move. That diaphragm is connected to a voice coil on most mics. A voice coil is a winding of copper usually that is aligned in tight spiral which creates an electromagnet when a electricity is ran through the wire. That electromagnet surrounds a earth magnet. When the electromagnetic voice coil is charged it and the earth magnet push or pull on each other When there is no noise the diaphragm does not move so the signal is the same going in as it is going out. If you say something the diaphragm vibrates causing the current coming out of the microphone to be altered by the resistance generated by the earth magnets push/pull on the electromagnet. In order for the mic to work it needs power.
This comes from a preamp. The preamp is where you plug the mic in. It will allow you to adjust the signal so that you can process it later. Or send it to an amp with out processing. The most common Preamp that you will recognize is your common mic mixer. todays mixers have lots of controls to adjust the final output of the sound you are recording. The main controls needed for your standard condenser mic will be your input gain AKA Mic sensitivity. This is an adjustment of the ammount of current passed through the mic cable. There are different types of Microphones and each one requires a different amount of power sent through them. Too much power and your mic will not be able to resist enough of the power and the returning signal will overpower the preamp and will sound like crap. If you looked at the signal under an oscilloscope it will look like a straight line if it is picking up nothing. If you talk into the mic waves will be visible. You can see what I mean using WMP10s visualizers it will be under bars and scopes. you want scopes. The preamp takes the signal and allows you to amplify it more so that you can output it to a processor.
A Signal [processor] is what it sounds like it takes something and it it handles it in a certain way. So a signal processor takes the signal and adjusts it in many ways. There are lots of processors So you only need to know that it takes a signal and then does something with it. Some more common Processors are crossovers, gates, compressors, Equalizers, DACs and much more. Lates take the Crossover for instance. The crossover takes the signal from the preamp and it separates the signal a couple of times and adjusts the signals into frequency bands. The good thing about this is that it allows you to use purpose built speaker types to generate quality sound replication. The Processors I use often are BSS omnidrives
. If you follow that link to the picture you will see a display that show some little humps. Each hump is a frequency band They overlap so that you don't loose part of your signal when you send it to the amps. Each one is sent out of the processor to an amp or amps in this case. I can tell by looking at the display that it will be sending six separate signals and the signals complement each other nicely creating a nearly flat output when combined with all the other outputs. The signals next stop is the amps.
The Amplifiers [Amps] They do exactly what you think they do. The amplify the signal from the Processor and amplify it and send it on to the speakers.
Considering we are sending out six signals you know that we have to have six inputs total on all of our amps or we will miss out on part of the full sound that we are trying to reproduce. So the amp takes the small signal and puts more power behind it so that it can be sent down some copper speaker wire to the terminals on the speakers.
The speakers. Speakers are the part that make the noise that is sent down the line from the mic and creates the same sound at much higher volumes. From the amps I said that the amplified signal heads down copper wires to the terminals on the speakers. These terminals are connected to a copper wire which is coiled just like the Mics voice coil. This coil is also called a voice coil. The voice coil of a speaker is also surrounded by a strong magnet that is connected to a paper cone which is designed to move air and make sounds.
I figures since I said that we had six signals I would explain what you would do with six signals sent to six different amps. This will allow for you to have a very precise sound system that is very loud and includes all kinds of drivers to make up several speaker cabinets for larger concerts and other large venues that require massive yet clear clean sound.
Oh yeah How do I incorporate the Digital signal into the above.
Hmmm. Well You take you analog mic and plug it into a analog mixer/preamp.
From the preamp we will send it into a signal processor which will use a Digital to Analog Converter [DAC] To change the signal into a digital image of the original sound image. The DAC basically takes a digital picture of the analog wave signal and turns it into ones and zeros. Why would we want to do that? Well copper can pick up noise from all kinds of things. And sending a signal along a copper wire for 200ft will also add resistance to the signal. If you run the wire next to power wire or a transformer you may pick up some noise in the signal. This will come out on the other side. So your digital signal can be sent on a copper wire as an electrical signal. You can also send it using light if your Processor has the output for it. The digital signal sent over coper wire can withstand much more interference than a analog signal on the same copper wire. If the signal gets to the next stage it should still be readable as a digital signal and the DAC will ignore the interference it picked up. Fiber optics don't have to worry about interference. Now that our Digital signal has reached the next stage you may get confused. Our signal came from a processor and now is coming into another processor.
This processor is going to take the digital signals and rebuild the analog signal so that it doesn't sound like a squealing modem when you send it to the next item in line. Yep another DAC. So now we have what we started with at the mic preamp.
Now that it leaves the processor we are going to process it again. Like before we want to separate the sounds and send them to different amps again. What would be the point of keeping the signal clean if we didn't have the gear to reproduce it in its full glory?
From the crossover we send multiple signals to the amps again.
From the amps we go to all the drivers in the speakers
In the gigs I do we use tons of processors.
From the mic we will send it into the mixer We insert a few processors to control the signal to allow us to prevent a few bad things from happening.
Here are a few of the Processors we use and what they do
Equalizer [EQ]: Like the crossover it allows you to adjust the signal by increasing or reducing its volume at certain a certain frequency. There are two types of EQs that I use. Graphic and Parametric. Used to tune the sound to your listening preference.
Graphic EQs: These are the ones you have seen. They have a fader for each band that you can adjust. Typically I use a 31 band 1/3 octave EQ.
This means that I can adjust the frequency in 31 places each adjustible frequency is 1/3 of an octave away from the next adjustable frequency.
Parametric EQs are often called sweepable EQs. Instead of having a fader you have knobs. your frequency knob can sweep through the frequency band to exact spots much more accurately than the graphic EQ. Then you have other knobs that boost or cut the selected signal. You also have a Q which adjusts how the size of the peak or notch that you are adjusting.
Used to hunt down feedback and eliminate it.
Compressor/limiter: This is used to take your signal and manipulate it so that the signal stay within a set of parameters. The reason why is because if the signal goes outside of the parameters you will get distortion and noise other than what you are trying to reproduce. If someone a singer belts out a note at high volume it may cause the signal to go above our preamps limit and it will PEAK. which will result in a really bad sound. If you have a compressor you can set your preamps threshold level and anytime you yell in the mic it will compress an signal and stop it from peaking. The other side of the usable signal area is on the bottom and is referred to the noise floor put a signal below this level and you also get noise.
Gates: A device that is like a reverse compressor. Once the signal reaches a certain limit the gate opens and the signal gets through. If the signal doesn't reach that level you will not hear anything.
Effects: Makes you sound different. Echo, verb, delay, chorus , and more.
Feedback was mentioned above and in case you didn't know Feedback is what happens when the sound that a mic is sending gets amplified enough that it reaches the mic again and begins a feedback loop which will increase in volume until you stop it. It usually occurs at certain frequencies so a good EQ can be used to eliminate it.
I think that just about covers Both setups for digital and analog signals as I would use them in a professional stage setup.
I also covered a lot more than was asked but it is an interesting read for anyone who wondered what is in all those racks back stage at a concert.
Ok no more topics that relate to my work while I am at work.