Ooh, what does this "Class A" switch do...?!!

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fbloke

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I've had my 5:25 Express for about 6 months now and have been searching for the right "crunch" sound. Last week I discovered a switch on the front saying "Class A"! I switched it on and the whole tone changed considerably for the better.

What does the Class A switch do to bring about such a change?
 
Hi ,
I am not sure if it is a " true " class A . Class A is defined as one power tube only .
There may be a few rare exceptions . Class AB1 is what " push pull " is , and what we
most use . Class A is in some opinions better sounding , it is also less watts .
A fender champ has one or two preamp tubes but ONLY one power tube , usually
an el84 . Some use a few other tubes .That is true class A as I was taught .

ab= one tube is at the highest point 180 and the other in theory should be at the lowest point -180 .
A = one tube that does the whole loop and you can really overdrive them at low wattage .
 
fbloke said:
I've had my 5:25 Express for about 6 months now and have been searching for the right "crunch" sound. Last week I discovered a switch on the front saying "Class A"! I switched it on and the whole tone changed considerably for the better.

What does the Class A switch do to bring about such a change?
Click to expand...


Geeez blokey - have you never looked at your Manual.
It's not a switch either - it's a light.
It is a true Class A amp and here's a hint. It's got something to do with the 5w switch.
Have you ever looked on the back. You'll find a little switch there - makes the light go on and off
 
LerxstLee said:
Hi ,
I am not sure if it is a " true " class A . Class A is defined as one power tube only .
There may be a few rare exceptions . Class AB1 is what " push pull " is , and what we
most use . Class A is in some opinions better sounding , it is also less watts .
A fender champ has one or two preamp tubes but ONLY one power tube , usually
an el84 . Some use a few other tubes .That is true class A as I was taught .

ab= one tube is at the highest point 180 and the other in theory should be at the lowest point -180 .
A = one tube that does the whole loop and you can really overdrive them at low wattage .
Click to expand...
That's why the Express series have 2 output transformers; the Class A switch disconnects one of the power tubes from the output.
 
Thanks for the replies, I find that the Class A switch also works when I'm switched up to the 30 watt setting. What with this feature, Contour and the sensitivity of the pots, the Express has an incredible range of tones for such a small box. It's my first Mesa and I'm seriously impressed.
 
I do not believe the 5:25 will operate in class A at the 25 (30) watt setting. It is definitely a class AB push pull configuration. As pointed out switching to the 5 watt setting will cause the amp to use a different OPT and operate the amp on one tube in triode.
 
Just kidding....... I cant imagine getting any piece of gear and not reading the manual......except maybe for the pedals that I've been acquainted with for 30 years.
 
I figured that out after I posted :oops:

soundchaser59 said:
Just kidding....... I cant imagine getting any piece of gear and not reading the manual......except maybe for the pedals that I've been acquainted with for 30 years.
Click to expand...
 

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