difference between buffer and booster?

[bent]

Hi everybody,

i really need some help to understand the difference , in really basic term ( my knowledge in electronic is limited) , between a buffer and a booster....i make a search but it's not clear to me....they talk about impedance and stuff like that , but i feel like homer simpson with all those term...   DOH !!!!

try to explain to me like if you explain to a 10 years old boy .... 

i really thank you for that....

bent

[Seljer]

buffer = generally has got unity gain, that means it doesn't make things louder or quieter.
Its purpose is to make differences in impedance not matter (generally has a high input impedance and a low imput impedance)
nice article describing impedance in pedals http://www.muzique.com/lab/imp.htm

booster = makes your signal louder, sometimes to overdrive a tube amp/whatever else you're running it into, other times just for more volume, can often double as a buffer...

[bent]

so if a understand well,

a buffer keep the signal to a same level....no more / no less than the original level....

and a booster rise the volume like a overdrive...

i just don't understand the end of your phrase  "can often double as a buffer"

bent

[zpyder]

i just don't understand the end of your phrase  "can often double as a buffer"

An amplifier (ie a booster) amplifies a signal... amplification is rated in gain (hFE) A gain of 2 means the signal is twice as loud.  A gain of .5 means the signal is half as loud.  A gain of 1 means the signal is the same volume.  This is sometimes refered to as unity gain.  A buffer essentially is a booster/amplifier with a gain of 1.  Within the circuitry of an amplifier/booster there is an opportunity (perhaps a requirement, not sure) to change the "impedence" of the signal.  Impedence is the stuff that's in the way that you have to push through to get to the other end.  And this is the main function of a buffer - it gives the signal enough "push" to get through that "stuff"

I asked pretty much the same question earlier at this thread: http://www.diystompboxes.com/smfforum/index.php?topic=48315.0
Might want to check out some of the answers I got there..

PLEASE LORD someone correct me if I am misleading this fella

cheers,
zpyder

[bent]

yahoooooooooooo.....

now i'm starting to understand....( after reading 8 times this posts  )

thank you very mutch SELJER and ZPYDER....it's getting more clear to me....

bent

long live the music

[Mark Hammer]

All stages/devices function appropriately to the extent that they are compatible with what comes before them and what comes after them.  The best dancer in the world will not look quite so graceful if their partner is a bad match for them in some manner, whether vastly different in weight or any of the three dimensions...or both. 

"Buffering" is the action or product of letting the "thing before" see what it likes/needs to see, and the "thing after" see what it likes/needs to see.  Before all this other fancy transistor/IC stuff, "buffering" or impedance matching would involve a passive matching transformer, that had one impedance on one side, and a different one on the other side.  So, the 1960's style transistor radio would have a matching transformer between the output stage and the speaker, that converted from what the transistor needed to see (generally something over 1k) to what the speaker needed to see (something that liked talking to 8ohm loads). 

Incidentally, buffering does not always involve going from high to low.  Sometimes it involves going the other way.  For instance, the old Les Paul recording guitars had fairly lo-impedance electronics, which were great for going into a console that expected to see 600-ohm microphones, but lousy for going into guitar amps that expected to see 5-10k guitar impedances.  So, the guitar included an lo-to-hi impedance matching transformer to provide an output that would make guitar amps happy.

Boosting simply involves any upwards change in signal level.  If the gain is set to x1, then obviously the output level is equivalent to the input level.  There MAY be an output impedance of the gain circuit that is different than its input impedance, but there doesn't NEED to be.  The same way you can have an interstage transformer that is exactly the same impedance on one side as the other (such as those Mouser 10k:10k transformers we use for octave fuzzes and the like). 

It often turns out that it is a simple matter for a circuit to have a much higher input impedance than it has output impedance.  In which case, a great many boosters end up being 2-for-the-price-of-1 because they not only provide boost but also provide some nice impedance matching.  Of course, one of the great ironies is that mismatched impedances end up in passive signal loss, so that even without deliberate boost being added, a unity-gain buffer will appear to add volume.

So, boosting and buffering are actions.  A "buffer" simply has a matching action.  A "booster" boosts.  Because of better matching, a buffer can sound like it adds gain (even though it simply loses less signal).  Because of how easy it is to build in the buffering/matching aspect, many boosters also function as buffers.  Because one can always reduce the amount of gain in a circuit, without having ANY impact on buffering/matching properties, by changing a single component, it is not uncommon for people to mentione preamps/buffer/booser in the same breath, figuring that the reader will know that all a booster often consists of is a buffer circuit with a small component change to get more than a gain of x1, or that all a buffer often consists of is a booster circuit with a small component change to drop the gain down to x1.

[zpyder]

Mark:

does a high input impedance "like to see" a low impedance introduced to it, and vice-versa?  i.e. is there a general rule of thumb that says "to drive the input of a high input impedance device, present it the output from a low output impedance device"?

zpyder

[oldrocker]

Already been through that.
http://www.diystompboxes.com/smfforum/index.php?topic=48230.msg357193#msg357193

[Satch12879]

Mark:

does a high input impedance "like to see" a low impedance introduced to it, and vice-versa?  i.e. is there a general rule of thumb that says "to drive the input of a high input impedance device, present it the output from a low output impedance device"?

zpyder

Do a search for "voltage dividers" and you'll have your answer to this...

Additionally, BOTH are amplifiers; one provides voltage gain, the other provides current gain.

[zpyder]

voltage dividers

Right... because the output impedance of one device plus the input impedance of the next device form a voltage regulator!  sweet... and we can calculate the output coltage of a voltage divider, and when we do we find that if the top half (1st device's output impedance) is relatively low and the bottom half (2nd device's input impedance) is relatively high, more of the voltage gets through....
bitchin'

as far as

Additionally, BOTH are amplifiers; one provides voltage gain, the other provides current gain.

I can see that this would be a requirement via ohm's law, but it's resulting effect on the circuit I am too naive to grasp... the voltage half I understand, since that is directly proportional to my signal's volume

cheers
zpyder

[Meanderthal]

 Simplest way I could put it: A buffer makes it sound clearer. A booster makes it louder, and maybe also clearer. Mark does a great job explaining how and why!
I like to think of a buffer as something like a tiny version of one of those electric company transformer stations that allow the juice to go on for miles and miles. I know it's not really the same thing at all, but the concept helped me understand what a buffer does...