I thought that speakers with greater resistance then the amp minimum resistance were not a problem.
I thought it was only a problem if the speaker resistance was below the amp's minimum.
This "rule" pertains to SOLID STATE amps only. Tube amps should be matched to a speaker load (e.g. 8 ohm amp output to an 8 ohm speaker).
I plugged the 8 ohm speaker cab into the 4 ohm plugin. There was a loud hum and now nothing. The 8 ohm side still works with a low hum where silence once abounded. I think it might be a filter capaciter. Any opinions???
Most tube amps can deal with a mismatched load of 100 percent. I can't really see how a mismatched load like your example could cause a filter cap to go south - but that inability doesn't mean it didn't happen.
What am I missing? These statements seem contradictory to me. Please explain. I'm trying hard to understand this aspect because I have two different tube amps and a solid state amp that must share cabs, so it is important that I understand this correctly.
Solarus with 8 & 16 ohm outputs
2000S with 4 & 8 ohm outputs
Concert Bass with I think two 4 ohm outputs that will handle a 2 ohm load if you plug 4 into each output jack but I'm not really sure of this but have never put greater then a 4 ohm load on it anyway.
Sorry, it's not my intention to hi-jack your thread, Eotpr
Tube amps should be matched to their speaker load to deliver their rated output power. But they can withstand an output mismatch of 100 percent without destroying their output transformer.
Since tube amps can withstand a direct short across the secondary output winding better than they can withstand a total open, I prefer to mismatch downward if a mismatch is necessary. In other words, I would plug in a 4 ohm speaker load to a tube amp with an output impedance of 8 ohms before I would plug in a 16 ohm speaker load to the same amp.
Just keep in mind that a mismatch between the output impedance of a tube amp and the speaker load is not the most desirable situation. But if it needs to happen, you will either not produce the rated output power or you will shorten the life of the output tubes... or both.
Solid state amps are the opposite. They will easily withstand a complete open (i.e. no speaker plugged in) and depending upon the amp circuit - could be easily destroyed with a shorted speaker load.
Solid state devices do not like heat. The lower the speaker impedance, the higher the current that will be drawn by the output transistors. The higher the current drawn by the output transistors the greater the heat they will produce. The greater the heat produced by the output transistors the shorter their life.
As I have mentioned in other posts, I would never use a concert with stock 2N3055 output transistors to drive a 2 ohm load. 4 - 2N3055 transistors will produce too much heat for them to have a long and productive life. Six or more 2N3055's - sure not a problem, but with only four they will be operating outside of their safety range.
