what is a load on a tube amp?

[distortedrumble]

the cabinet i bought says to never connect a tube amp without a load connected to it. I'm looking at the marshall avt150 and i dont want to destroy the thing when i get it. is the load already on it or is this something else i need to buy?

 

[faderbug]

when you turn on a tube amp (and older solid states ftm) it has to be connected to a speaker otherwise it goes up in smoke. presumably that's the load they're talking about.

and make sure the impedance levels match.

 

[juststartingout]

Yes, the speakers are the load they are refering to.

 

[distortedrumble]

what about Ohms? if the amp is 4 ohms and the cabinet is 16...is there a switch on the amp most of the time or is that not important?

 

[faderbug]

the impedance of your speakers must always be higher thn that of your amp.

 

[savageblues]

The general rule (atleast for Fender tube amps) is that a 50% mismatch is tolerable. If the output impedence of the amp is 8ohms, then either a 4 ohm cab or 16 ohm cab will work OK (with some loss of power and frequency response).

Too much of a mismatch is a problem, even if it is higher than the recommended load. For example a 16ohm cabinet is NOT recommended for a 2 ohm Super Reverb amp.

Marshall amps are much less tolerant of mismatches from what I hear, but often come with impedence selector switches. I would not try running a 4ohm Marshall with a 16ohm cabinet.

Good luck.

 

[juststartingout]

I think you will find that the AVT 150 has 3 different jacks for speakers, 4,8,16. Just hook the speakers up to the apropriate one.

 

[Scottgman]

If I'm not mistaken, aren't the Marshall AVTs actually the new Valvestates? Meaning they are hybrid SS/Tube amps with a SolidState power section and a tube pre-amp.

I used to have a Marshall Valvestate 100-watt combo and I would unplug the speaker so I could run direct into the mixer with no external sound coming from the amp. I did this many times with no apparent harm to the amp.

You might want to check with Marshall to verify if running an AVT without a load would be problematic.

 

[distortedrumble]

http://www.americanmusical.com/st/aspx/i-MAR+AVT150H/en/item.htm yeah i think your right...this is like tube pre and solidstate power

 

[bongolation]

The general rule (atleast for Fender tube amps) is that a 50% mismatch is tolerable. If the output impedence of the amp is 8ohms, then either a 4 ohm cab or 16 ohm cab will work OK (with some loss of power and frequency response).

A number of recent amps I've bought warn strenuously against use of a speaker of any lower impedance than the output. Slightly higher is OK. Not lower.