Stupid question about W and

[Flow Of Time]

Soo.. I heard that if you plug, for example, a 100 W at 8Ω amp into a 16Ω cab, it shouldn't hurt the amp. But the output power will be reduced by 50%.
First of all: Is this even true?

And the second question:
If I'd set my 6505 to 4Ω, and then plug it into a 16Ω rated cab, would it reduce the output power by 75% (so 30W would remain) ?

I'm asking this, because atm I only have a 60W rated PPC 1x12 cab and can't use my 6505...

 

[~BURNY~]

Soo.. I heard that if you plug, for example, a 100 W at 8Ω amp into a 16Ω cab, it shouldn't hurt the amp. But the output power will be reduced by 50%.
First of all: Is this even true?

True: it won't hurt the amp

False: it won't reduce the power

And the second question:
If I'd set my 6505 to 4Ω, and then plug it into a 16Ω rated cab, would it reduce the output power by 75% (so 30W would remain) ?

I'm asking this, because atm I only have a 60W rated PPC 1x12 cab and can't use my 6505...

No, it won't reduce the power.




You can use your 6505 without problems as long as you don't push the master volume (post gain) too high. Don't go over 3, maybe 4 and you'll be fine and it will be plenty loud.

 

[Flow Of Time]

Awesome, thanks for explaining!
I probably won't even go as high as 1, since I can only use it in my bedroom right now..

Edit: Damn, if this method is really safe, I'd recommend it to every fuck who thinks he needs to have 6505 in his bedroom. This is the first time I got usable results at a non hurting level. The sound I got with my 2x12s back then weren't even close (at that volume of course)

Edit N°2: I had to record a short clip: https://copy.com/9Bm0hHS3ng2o
This is at a really moderate volume. You can hear the metronome and the strings pretty clearly

 

[TheWinterSnow]

Soo.. I heard that if you plug, for example, a 100 W at 8Ω amp into a 16Ω cab, it shouldn't hurt the amp. But the output power will be reduced by 50%.
First of all: Is this even true?

With tube amps, this isn't entirely true, but 99% true. Depending on the transformer design, no it won't hurt the amp as king as reasonable loads are used.

And the second question:
If I'd set my 6505 to 4Ω, and then plug it into a 16Ω rated cab, would it reduce the output power by 75% (so 30W would remain) ?

I'm asking this, because atm I only have a 60W rated PPC 1x12 cab and can't use my 6505...

Like I said, about 99% true, there are some things in the transformer that effect output power and whatnot but are usually pretty minor. Regardless putting a larger load will reduce power.

I won't go into a long write up on the topic but I did write this blog on the topic which may or may not help further.

http://corvusaudio.blogspot.com/

 

[Flow Of Time]

I read the post, it explained a lot So this method should be essentially safer than pluging it into the 60W cab at 16ohm, because I wouldn't risk pumping over 60W into the cab, since im running the amp at 30W... Right?^^

I don't get where the missing 1% is coming from, though.. Is the tube life beeing shortened here aswell?

 

[~BURNY~]

Well, Dwight isn't always 99% then.

 

[Flow Of Time]

 

[TheWinterSnow]

I read the post, it explained a lot So this method should be essentially safer than pluging it into the 60W cab at 16ohm, because I wouldn't risk pumping over 60W into the cab, since im running the amp at 30W... Right?^^

I don't get where the missing 1% is coming from, though.. Is the tube life beeing shortened here aswell?

The 1% isn't an exact number I was just using that to describe that there are some other factors in reduction of power when having a transformer, there are DC resistances that play a role in the total load to the tubes and as a result you don't get as much reduction as you would expect. Not necessarily a problem with Solid State amps, they really do have a linear reduction as you would expect. How much of a loss of reduction do you get? I do believe its the ratio of the DC resistance winding acting as a voltage drop over the AC resistance, could be anywhere from 34 watts to 47 watts instead of 30 watts. Very crude estimate as I am not 100% sure how to calculate it so don't quote me on it but that seems about right.

I also think that was what Burny was talking about.

Will is reduce the life of the tubes, no. The only to things that reduce tube life outside total abuse such as electrode arching (from over voltage and overdissipation) is higher dissipation or higher current and since you reduced both, well they will actually last longer.

 

[Flow Of Time]

Well, that's awesome! The exact ammount of reduction loss doesn't really matter that much anyway, as long as the end result is below 60W.
Just out of curiosity: Is this the way attenuators work?

 

[TheWinterSnow]

Just out of curiosity: Is this the way attenuators work?

No, attenuators operate differently. They run voltage dividers that when connected to a cabinet maintain a constant impedance to the amp, but the amount of power delivered to the cabinet is reduced and instead ran through a dummy load.

 

[CraigJohnsJr]

60% of the time, it works every time...