The argument for operating class-Quick and Dirty
Jun 2, 2006 20:41:02 GMT
Post by rickcr42 on Jun 2, 2006 20:41:02 GMT
I beleive most if not all audio circuits should operate in a pure Class-A topology but that is the most inefficient method of amplification there is with a good portion of the output power being no more than heat plus most stage cost going to casting off that heat and power supply design which if the circuit is single ended especially will make or break the amp.
The reason behind my choice is low level information.These are the little sounds that flesh out or complete the overall performance that while not essential to music enjoyment is the only way you can hear these low level signals as actual involving music rather than just sounds that bridge loud passages.
ever notice that as you lower the volume with either a speaker or headphone based sound system the "life" seems to get sucked out of the music as the volume lowers ?
that no longer is the performance organic but instead becomes lifeless sounds that demand you up the volume again ?
Class A means the respnse to music is instant because the amplifying device is always on all the time and thast at full power while every other topology means the amplifying device must respond to the signal which means recognize it then react to it losing the beginning of every signal so no matter how minute that loss still a loss.
Class-A always on ready to pass whatever is at the input but at a higher level
Class "everyhging else" sitting and waiting to respond
Because of the heat generated by pure class a operation and the sheer cost of this inneficiency engineers have wrestled with ways to get good performance vs. product cost so over the years we have seen most efforts aimed at getting more crammed into smaller spaces that run cool and with relaxed power supply requirements.
Great news for a cell phone or a portable player,great news to receiver manufacturers or budget audio manufacturers,and great for the DIYer who has no clue mostly and would be lost reading a data sheet then designing an amp from scratch but has relaxed expectations to a point where a "natural" sounding amp is now called dull while one that is seriously lacking will be called "detailed".Combine that with digitalis or worse,lossy compresssion and you have the sound of the new milenium in a nutshell-dry sterile non musical equipment each touting why theirs is the better choice with the end users asking questions like "what can i use to add some "warmth" to my system when what they really want is restoration of ALL the music presented in a way that is pleasing to humans.
adding warmth is a bandaid on an open wound and no cure.You do not spray perfume on a skink then declare the skunk scent free so rather than try and gloss over system limitaions by adding a veil it is maybe a smarter decision to begin without the viel then upgrade each stemic weak link until you have all the music all the time and that means you must have circuits that pass information not react to information !
Think of it like being mugged in a dark alley.You are walking past,someone snatches your ass into the alley then robs you and maybe even beats you then leaves.At that time you call the police who hopefully will catch that scumbag but even if they do YOU ARE STILL MUGGED !
Catching the POS will not change what has already transpired so the best you can hope for is the satisfaction that the person will be punished.
Music is like that.Once signal is lost you can never regain the notes only accept that you have and make the best out of what is left.
THAT is why Class-a operation is a superior method of amplifying an audio signal.Music flows and changes so if the circuitry is continuously in a catch up mode how accurate is the signal you are listening to ?
If there is a downside other than the before mentioned heat generation and added cost it would be ultimate headroom which if pure class-a is at ZERO !
There is no more power supply or amplification left and that means right to overload.This overload anything from nasty (SS) to notr so nasty (valves) but still there without very careful system matching for power output/transducer sensitivity
Lucily there is a "cheat" in there that allows us to both keep the cost and heat down and that is High bias Class-AB where for ALL low level signals operate in the linear A region with class AB reserves for the peak music event.
Being louder in actual volume than both the low level music signal and the majority of the music which resides in the middle any lost detail is not noticed anyway,especially if the passage is a complex one with multiple events (BUSY signals) so a nice way to have your cake AND eat it too
Translated over to power amps this would be Class-a at the front end and driver stages with a high bias Class-AB output stage as is done with most of the known opamp/discrete output headphone amps and why they mostly sound as they do
The reason behind my choice is low level information.These are the little sounds that flesh out or complete the overall performance that while not essential to music enjoyment is the only way you can hear these low level signals as actual involving music rather than just sounds that bridge loud passages.
ever notice that as you lower the volume with either a speaker or headphone based sound system the "life" seems to get sucked out of the music as the volume lowers ?
that no longer is the performance organic but instead becomes lifeless sounds that demand you up the volume again ?
Class A means the respnse to music is instant because the amplifying device is always on all the time and thast at full power while every other topology means the amplifying device must respond to the signal which means recognize it then react to it losing the beginning of every signal so no matter how minute that loss still a loss.
Class-A always on ready to pass whatever is at the input but at a higher level
Class "everyhging else" sitting and waiting to respond
Because of the heat generated by pure class a operation and the sheer cost of this inneficiency engineers have wrestled with ways to get good performance vs. product cost so over the years we have seen most efforts aimed at getting more crammed into smaller spaces that run cool and with relaxed power supply requirements.
Great news for a cell phone or a portable player,great news to receiver manufacturers or budget audio manufacturers,and great for the DIYer who has no clue mostly and would be lost reading a data sheet then designing an amp from scratch but has relaxed expectations to a point where a "natural" sounding amp is now called dull while one that is seriously lacking will be called "detailed".Combine that with digitalis or worse,lossy compresssion and you have the sound of the new milenium in a nutshell-dry sterile non musical equipment each touting why theirs is the better choice with the end users asking questions like "what can i use to add some "warmth" to my system when what they really want is restoration of ALL the music presented in a way that is pleasing to humans.
adding warmth is a bandaid on an open wound and no cure.You do not spray perfume on a skink then declare the skunk scent free so rather than try and gloss over system limitaions by adding a veil it is maybe a smarter decision to begin without the viel then upgrade each stemic weak link until you have all the music all the time and that means you must have circuits that pass information not react to information !
Think of it like being mugged in a dark alley.You are walking past,someone snatches your ass into the alley then robs you and maybe even beats you then leaves.At that time you call the police who hopefully will catch that scumbag but even if they do YOU ARE STILL MUGGED !
Catching the POS will not change what has already transpired so the best you can hope for is the satisfaction that the person will be punished.
Music is like that.Once signal is lost you can never regain the notes only accept that you have and make the best out of what is left.
THAT is why Class-a operation is a superior method of amplifying an audio signal.Music flows and changes so if the circuitry is continuously in a catch up mode how accurate is the signal you are listening to ?
If there is a downside other than the before mentioned heat generation and added cost it would be ultimate headroom which if pure class-a is at ZERO !
There is no more power supply or amplification left and that means right to overload.This overload anything from nasty (SS) to notr so nasty (valves) but still there without very careful system matching for power output/transducer sensitivity
Lucily there is a "cheat" in there that allows us to both keep the cost and heat down and that is High bias Class-AB where for ALL low level signals operate in the linear A region with class AB reserves for the peak music event.
Being louder in actual volume than both the low level music signal and the majority of the music which resides in the middle any lost detail is not noticed anyway,especially if the passage is a complex one with multiple events (BUSY signals) so a nice way to have your cake AND eat it too
Translated over to power amps this would be Class-a at the front end and driver stages with a high bias Class-AB output stage as is done with most of the known opamp/discrete output headphone amps and why they mostly sound as they do