Hello Everyone!
Apr 5, 2013 at 8:33 AM Thread Starter Post #1 of 2

hedfonewb

New Head-Fier
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My name is Brandon and I'm new to the forum. In fact, I'm 19 and new to just about everything!
 
I never really much liked the music I grew up with and, like most people my age, whatever I heard was coming from iPods and MP3 players, mostly. Recently, my uncle got me into listening to his music on a killer "old time" stereo system (like, from the 90's) and I got completely hooked!
 
Since then I have been trying to learn about how stereos work and want to put together something for my room. I would mostly be listening to headphones for now but want to plan for the future when I get my own place. I was hoping that maybe you guys here could give me a sort of "Stereo 101" intro. Here's what I (think) I know:
 
The source takes the information from the media. If it is digital, it has to go to a DAC to convert it to analog. This signal goes to a preamp to step up the signal enough to go to a power amplifier. The power amp increases the signal power so that it can move the speakers to create sound waves we can hear. Is this about right?
 
Here's what I don't get: when you are using a preamp and a power amp and headphones, the headphones plug into the preamp. How does the signal from the power amp get back to the preamp and the headphones?
 
Thanks, Brandon
 
Apr 5, 2013 at 1:52 PM Post #2 of 2

kramer5150

Headphoneus Supremus
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Welcome to HF... sorry about your wallet.
 
You've got the basics.  Its all really about signal conversion, attenuation, amplification from one stage through the next.  The sonic information originates from a grove pressed into vinyl, magnetic particle on tape, or digital bits put together in a stream.  Its all a big conversion process, the final result is oscillating air pressure waves picked up by our eardrums.
 
I try to think of things in terms of dedicated PROCESSES, as opposed to dedicated components.  Data originates in a stream from CD, or storage drive.  The source outputs the data stream via USB, toslink or Coax.  It next gets converted from digital stream to an analog AC signal.  That in itself (usually) is a preamp level signal, ready for amplification gain-stage.  However that preamp level signal is usually altered, switched, colored or split via a dedicated preamp stage.  From there the signal gain is increased/attenuated in an amplification stage.  From there the the resulting boosted/attenuated AC is converted to oscillating sound pressure waves that can be heard by our ears.
 
In terms of traditional dynamic headphones (for the most part) the entire signal chain is "preamp level" signaling.  Typical dynamic headphones only need a fraction of the wattage required by speakers, so in head-fi-ville the entire signal chain (post DAC process) is in the realm of a preamp level.
 
So thats a VERY basic, general way to look at it.  In reality though its not that cut and dry.  Most high end headphones benefit greatly from reserve amplification.... IE extra buffered current, and extra voltage swing capacity.  I am not sure why this is the case... it just is.
 
To further complicate things there are multi-function components that serve multi-process functions.  Most DAC components have headphone amplifier outputs, as well as preamp output and digital input source switching.  Many headphone amps have headphone level outputs as well as preamp level outputs, which in reality can be very similar in overall wattage output capacity... but vary in terms of output impedance.
 
On that note, impedance matching is probably the most miss-understood element of system synergy, between the various processing stages.  
 

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