Class A overdrive -- definition

[mordechai]

I have heard conflicting definitions for what constitutes a "class a" overdrive circuit.  I THINK it means that an initial gain stage is constantly running full bore and that gain variation occurs at subsequent stages.  Is this right?  And what are the benefits of a class A type of overdrive as opposed to other types, especially in pedal design?
 

[merlinb]

It usually means the circuit is entirely single-ended, and not push pull. The term is often misused. There are no special benefits, it's just a marketing thing. People think the letter 'A' is better than the other letters.

Class A has nothing special to do with overdrive. It simply means the device (whatever it may be) is conducting current during the full 360 degrees of audio cycle. A lot of overdrives rely on cut-off clipping to get their distortion, which means they're not actually operating in class A any more! (Class AB).

[earthtonesaudio]

JAMO, just another marketing oxymoron.   

[R.G.]

And what are the benefits of a class A type of overdrive as opposed to other types, especially in pedal design?

Solely that it looks cool in advertising copy to people who don't know what it means.

It's a little like

"DANGER!! 50,000 OHMS!"

[ayayay!]

And what are the benefits of a class A type of overdrive as opposed to other types, especially in pedal design?

Solely that it looks cool in advertising copy to people who don't know what it means.

It's a little like

"DANGER!! 50,000 OHMS!"

Haha!  I actually almost fell for that for a second.   

[Bill Mountain]

And what are the benefits of a class A type of overdrive as opposed to other types, especially in pedal design?

Solely that it looks cool in advertising copy to people who don't know what it means.

It's a little like

"DANGER!! 50,000 OHMS!"

Sig'd

[petemoore]

   Don't forget that Ohms can now be cloned !
  You want the 'original ohms', copies just don't hold a candle to the original.

[petemoore]

  Single ended tube amp output distortion...has nothing to do with anything really except exactly that [which raises the question 'exactly what is that?'...unless someone can sell it as having to do with something else...and a third party or parties buy into that or some other rediulous notion.
  "Class A Overdrive'' has a nice ring to it [like first class !].

[earthtonesaudio]

The brutal reality is that some of guitarist's favorite tones probably come from class b or even c operation.   

[defaced]

The brutal reality is that some of guitarist's favorite tones probably come from class b or even c operation.   

Logic or facts will not be tolerated in this discussion 

[DDD]

Maybe, "Class A Overdrive" means that the overdrive produces more even harmonics than the odd ones, like SE output stage does (?)

[bhill]

No, class A means a clean pp signal, no distortion. Look at the previous posts.

[R.G.]

In the immortal words of William Jefferson Clinton, it all depends on what your definition of 'is' is.

Much advertising is presented as the absolute truth, and achieves legal truth (which is different) by being content-free.

[fuzzy645]

In the end, it is up to consumers to be as close to "educated" as possible before shelling out hard earned bux.

There will always be someone looking to sell you a bridge, and not just in the musical product industry.   Its just that you find an awful lot of this kind of stuff in the music industry (IMHO) because there are plenty of takers.

In the defense of the manufacturers,  I would also add that if a company sells a great sounding amp or pedal, and they manage to get a consumers attention by mentioning that the amp is "Class A", I suppose more power to them, provided they aren't lying.  For example, Fulltone advertises their Fat Boost pedal to be Class-A and I don't think anyone would doubt their credibility/integrity.

[FiveseveN]

People have been trying to find an objective reasoning behind matters of taste since the beginning of recorded history.
About as long as they've been exploiting ignorance for financial gain.
I believe this is where memes like "Topology/device/vintage X sounds better" come from.

[JDoyle]

"Class A" means that the output device or devices, it doesn't matter how many, operate throughout the entire signal swing.

But the reality is this: If it is a circuit in a pedal running off of 9V, it's almost guarenteed to be class A. Class A is the cleanest, the least sensitive to bias arrangements and normally has less parts to possibly fail. The only reason to move out of class A is to limit power dissipation in the output devices. And at 9V and a couple of milliamps, dissipation is rarely a concern.

In my opinion, the prime example of a "Class A Overdrive" would be the Rangemaster.

Regards,

Jay Doyle

[darron]

i had a thought and if i told someone "class A overdrive" i probably mean that instead of clipping diodes etc. it's rather stacked transistors running really hot. i think the last stage of the BSIAB2 is like that for example? it might even suggest not a negative feedback setup like some fuzzes nor a microAmp setup.

[petemoore]

  For small signal devices...show me the schematic, ''whatever'' is my harumph to 'super precision components'' or ''1rst class" or any of that nensonse. I do fine with my regular capacitors and resistors and never really had a problem I couldn't solve with them.
   For amplif iers it's similar ''show me the schematic'' but I'd add ''show me Exactly [as in precisely...including references to what transformers etc.] what is in it.
  Any units may have ultra components and precision handiwork and anything else...but what does it actually 'do' besides tweek my lust for the useless language of desire Vs. actual quality ?
   ...it mainly boils down to 'what does it do?'...then, 'how well does it do it ?' all the other jargon falls away once the learning process is well on it's way to having been learnt.
   Either learn to read 'n cypher, or prepare to get burnt before you learnt.

[gmoon]

No, class A means a clean pp signal, no distortion. Look at the previous posts.

Not exactly no distortion, just no distortion via clipping. There can be other non-linear aspects that shape a waveform in Class A...

...and their importance is usually overstated for guitar amps.

[bhill]

That is pretty much what I meant. Especially your last line.