What is the power output of my guitar amp?

jonislost · 31 Jul 2009 at 14:18

I've just got my first guitar head and cab and I'm just trying to cure my own curiosity (and google is failing me!)

The head has a 125 Watt output
The Cab has 200 Watt output

What is the output when I play through this? 200 watt or 125 watt? :confused:

Does the head limit the cab?

I could be barking up the completely wrong tree either way, and it's way more than loud enough (nice neighbours!)

Cheers!

MikeHunt79 · 31 Jul 2009 at 14:18

125 watt

jonislost · 31 Jul 2009 at 14:20

MikeHunt79 said:
125 watt

That was fast! Thanks!

So, do you know what the point is in having a full stack rated at 400 watts when even the highest price heads only output 100 - 125watts? Is it just image or what

? Am i understanding power vs sound output incorrectly?

just Scott · 31 Jul 2009 at 17:05

What amp and cab do you have?

SexyGreyFox · 31 Jul 2009 at 19:46

And then throw into the equation the difference in volume between valve & digital.
My lead guitarists 60 watt Marshall valve is way louder than my 150 watt Marshall digital.

jonislost · 31 Jul 2009 at 23:44

Amp head is a Bugera 6262 120watt valve
Cab is Bugera 412H-BK 200 watt (4x12inch)

Haven't had it past volume 2, so I don't even know where the sweet spot is yet, will be able to push it further on Sunday in the practice room.

Coming from playing a Line 6 Spider II 75 watt combo, this is like heaven to play through, even at these low volumes

jak731 · 1 Aug 2009 at 00:14

The amp used in a system is always the limiting factor in terms of power output. The power rating of the cab is useful because it is usually a thermal rating, ie at which point the voice coils will overheat, not necessarily the point at which the bass speakers will smash themselves apart beyond their maximum excursion at low frequencies. So a higher rated cab is more assuring that it will continue to work fine at the maximum output of your head. The maximum sound pressure is determined by the sensitivity of the cab and power output of the head. For instance if the sensitivity of the cab is 96db @ 1W @ 1m and the power output of the head is 100W the maximum volume will be 116db, off the top of my head i think this is worked out by sensitivity + 10log(power max). This means the sensitivity of the cab is far more important in terms of maximum volume than the power output of the head, as an increase in 10db of sensitivity is the same as going from a 100W to a 1000W amp.

Obviously at the end of the day quality is far more important than max spl, as anything over 90db is potentially doing damage to your hearing anyway, so if you have a sensitive cab you don't really want to be outputting more than 1W in a home environment anyway.

That's one reason horn loaded cabs are so popular in venues, they can add 10db of sensitivity when using the same driver compared with a sealed unit, and ported subs tend to be loud at one boomy frequency so lack quality.

Sorry for the long post.