Buffers Talk

[HOTTUBES]

Noob questions here ......

Whats the reason for using IN & OUT buffers ?
Whats the pro's & cons of both ?
What makes up a good buffer ?

[R.G.]

Whats the reason for using IN & OUT buffers ?

They serve two different purposes.

Whats the pro's & cons of both ?

Cons of both:
- You have to pay for a buffer circuit.
- You have to do a good job of designing the buffer; you can't slop it up and get good results. Generally, this gets a posting at The Gear Page that says "all buffers are crap".
- You can't stuff any signal, no matter how big, into a buffer and get good results. Buffers are designed to work with a certain maximum signal size, generally somewhat to much less than their power supply. Go outside that and many buffers, especially inexpensive ones, misbehave. This is not really a con of the buffer per se; it's more a limitation of the intellectual size of the user. Generally, this gets a posting at The Gear Page that says "all buffers are crap".

Cons of input buffer:
- in certain highly specific circuits of which the Fuzz Face is the prototypical example, an input buffer can make distortion too harsh. Generally, this gets a posting at The Gear Page that says "all buffers are crap".

Cons of output buffer:
- an uninformed user might use an output-buffered effect before a Fuzz Face or similar, then wonder what happened. Generally, this gets a posting at The Gear Page that says "all buffers are crap".

Pros of input buffers:
- you can run a raw guitar input into them, and if they are well designed, you reduce treble loss ("tone sucking") to only what the cable from guitar to buffer causes. This can masquerade as a "con" if the user liked the "brown sound" (AKA "tone sucking" - they're the same thing) of a long cord and loss of treble. But most users think it's a pure  pro
- you can drive whatever the input of your amazing new effect circuit is without worrying about loading the guitar.

Pros of output buffers:
- you can load the #@$*# out of them with splitters, long cables and other junk and they still work fine.
- the prevent any effect downstream of them from loading the guitar's signal.

What makes up a good buffer ?

- high input impedance, generally in excess of 1M over the whole audio spectrum
- low output impedance, less than 1/10 of whatever you'll hang on the output, over the whole audio spectrum;
- immunity to short circuits on the output
- low distortion, both THD and IM
- as wide an output swing as you can afford so big signals from users sporting Dynamic MegaBoosters powered from 48V car batteries don't overload it.
- as wide an input range as you can afford so that big signals from users sporting Dynamic MegaBoosters powered from 48V car batteries don't overload it.
- for well designed buffers, some thought about what happens when a user plugs a speaker output from a 5kW PA amplifier into its input and wonders whether this will sound great, or when the same user plugs the output through and adapter cable into a 240VAC wall socket to see if it can reverse drive the power grid.
- gain is generally unity, but does not have to be. Sometimes buffers have a little gain, but it's unusual to have it be large.

[brett]

for well designed buffers, some thought about what happens when a user plugs a speaker output from a 5kW PA amplifier into its input and wonders whether this will sound great, or when the same user plugs the output through and adapter cable into a 240VAC wall socket to see if it can reverse drive the power grid.

 

[R.G.]

You might wonder - was R.G. just engaging in creative hyperbole or has he run into real incidents that make him say things like that.

You guess which. 

[HOTTUBES]

Thanks RG for the info on Buffer's ...great info as always !!!

[boogietone]

Yeah. Bu bu bu but, All Buffers Are Crap.