how to reduce wattage on a 5150

[Wolfeman]

Isn't the whole point of getting an amp with 100 watts or more so you can have the headroom to retain a good tight end without too much sag, and so you don't have to induce unnecessary compression from the poweramp?
Correct me if I'm wrong, but I'm pretty sure that's like, half the reason why someone would buy a 5150, JSX, Dual/Triple Recto etc etc in the first place.

Yep. And to be incredible loud at band practice.

 

[TheWinterSnow]

Yep. And to be incredible loud at band practice.

we are guitarists, we believe in our own minds that we can never be loud enough, and in my reality, this is true

Isn't the whole point of getting an amp with 100 watts or more so you can have the headroom to retain a good tight end without too much sag, and so you don't have to induce unnecessary compression from the poweramp?
Correct me if I'm wrong, but I'm pretty sure that's like, half the reason why someone would buy a 5150, JSX, Dual/Triple Recto etc etc in the first place.

Its a double edged blade. When you want to record in your home and want that warmth of power tube saturation, but you don't want to wake your neighbors, what do you do? You make the power amp saturate at lower volumes by reducing your output power. On the other hand, when playing at band practice or a gig, you want to be loud and tight as possible.

 

[kaomao]

Isn't the whole point of getting an amp with 100 watts or more so you can have the headroom to retain a good tight end without too much sag, and so you don't have to induce unnecessary compression from the poweramp?
Correct me if I'm wrong, but I'm pretty sure that's like, half the reason why someone would buy a 5150, JSX, Dual/Triple Recto etc etc in the first place.

it's because you GOTTA KILL PEOPLE IN FRONT OF YOU

 

[Jarkko Mattheiszen]

have you ever messed around with the impedance switch with the same load to see how different the amp sounds? It makes a huge difference in tone, the lighter the load is, the more bright/brittle, lacking bass the tone will have. Quick explanation, as I couldn't find what you were talking about in the FAQ, but the tubes are connected in parallel with each other, which means they receive the same voltage drop and the total current is controlled by the number of parallel connections. Since you remove half of the tubes, you reduced the output current by half. The two tubes that are still in the amp will be conducting the same current each regardless of how many tubes are in the amp (this is an effect of parallel circuits). What happens is that your load will not give you the same current because the voltage does not change, you have to match the load so that the current on the secondary tap matches the current you want the tubes at, and since you do not rebias and you want the current the same, that means the load has to change, it has to double. To compensate, you can use the same load if you drop the voltage in half, producing the correct current (the dissipation will now be equal on both sides).

Now unless their is something that I am forgetting offhand regarding transformers, that is correct. This also means that, if using ohms law on the situation on a load circuit, if you remove two of the tubes and keep the load unchanged, since the tubes were in parallel, the remaining tubes will double their current to compensate as the amount of current they pull will be determined by the load. This means that a 100 watt amp with 4 tubes on 16 ohms will also dissipate 100 watts with 2 tubes at 16 ohms. I can also say that is why manufactures specs for solid state amps specify the power dissipated depending on what type of load you use (ex 250w @ 16ohms, 500w @ 8 ohms, 1000w @ 4 ohms, 2000w @ 2 ohms) because SS power amps do not have a transformer, they cannot be adjusted for, so their maximum output is determined by the load.

Makes sense, cheers for making it clear. I have messed with the impedance switch with tubes pulled, but on my Windsor it didn't seem to have that much of a dramatic difference. I was more worried if it's safe to either leave the impedance where it was or switch one step down

 

[TheWinterSnow]

If everything is in general safe zones you won't notice a difference. For example, when I have my 5150 hooked up to an 8 ohm load, switching the tap from 8 to 16 doesn't make any difference other than the 16 being a tad bit louder. You will find in electronics as almost everything in life that the theoretical operation never matches the real world operation. Still in terms of current/power its better safe than sorry even if it doesn't impact the tone, because all you will end up doing is shortening the life of your tubes.

But I am glad I could help out.

 

[bryan_kilco]

Then I'm calling you an idiot. The 5150 is loud as fuck at post 3-5 no matter what you do to it sans the suggestions your telling everyone to fuck off with.

I kinda felt the same way...

"hey, help me out but but dont tell me this or this..."

 

[SuperD]

Variac. Dial down the voltage. Post at 4-5 is no problem. No attenuator, same amp, same cab, bedroom volumes, full saturation.
Unfortunately there may be some other, less desirable effects on the internal components of your head, like the tubes and transformer.
Like, they'll eventually fail.
So, your call...

 

[TheWinterSnow]

Variac. Dial down the voltage. Post at 4-5 is no problem. No attenuator, same amp, same cab, bedroom volumes, full saturation.
Unfortunately there may be some other, less desirable effects on the internal components of your head, like the tubes and transformer.
Like, they'll eventually fail.
So, your call...

throwing a variac down will not go through tubes faster as you essentially are bringing the maximum output/amplifying voltage possible. This does effect the biasing of the amp however.

 

[Fragle]

wow....so much hate...

anyways, regarding power amp saturation at lower levels. to be honest, with modern "heavy" amps a large amount of the tone comes from the preamp section, unlike an older marshall for example which relies on power amp saturation to get "its" tone.
moreover, IMHO power amp saturation is rather saggy, which sometimes can be undesirable if you're shooting for a super tight "modern" tone.
what i'm trying to say is, attenuating the volume to get into the saturation zone earlier is not necessarily the ticket to a great tone.
what you need to do (once again imho) is turning the volume up to get some cabinet involvement and speaker excursion going on. speakers sound much different when driven hard, and most of the time different = better in that particular case.
and that's something no attenuator will give you, it's solely a matter of VOLUME.

btw, i'm not talking SUPER FUCKING INSANE loud here, just enough the get the speakers working nicely. on a 5150, that spot seems to sit around 3/10 post gain. imho

 

[Wolfeman]

btw, i'm not talking SUPER FUCKING INSANE loud here, just enough the get the speakers working nicely. on a 5150, that spot seems to sit around 3/10 post gain. imho

^ I agree with this statement.

 

[dani]

variac's are a really bad idea for tube amps, reducing the heater voltage even marginally will seriously shorten tube life.

thanks,