1959 Plexi clone sounds harsh after blowing the HT fuse

[Chuck H]

Well he IS using an attenuator and mentioned that the master vol on the amp was never above three quarters

[bob p]

Yeah, I read all that. But speakers don't break by themselves. There's something going on, more than meets the eye.

What kind of real power is the amp putting out? We don't have a clue. Depending on the taper of the MV pot on his kit amp, 3/4 could be a pretty strong signal with a 1959. The power that the amp is producing is relevant. Let's get a number.

And how do we know that his new attenuator works as intended? It's brand new, he just hooked it up and now he's reporting problems at the speaker.

If I had this problem I'd be taking power measurements everywhere in the signal chain. I'd probably end up sweeping a signal into the speaker to determine what sort of conditions make the speaker sound bad.

I'd rather have some solid numbers to hang my hat on, rather than relying on "the master was only up to 3/4" and "I'm using a brand new attenuator."

[Chuck H]

The vagueness of my indicators was the reason for the wink emoji. Indeed, earlier when I mentioned that a 1959 could put out over 200W peak when clipping was when Mrk200 mentioned that the master was only up three quarters. Also a reason for the wink emoji because if the preamp is cranked up it's possible the power tubes could be clipping at that master setting. Meaning full power. The master volume is a GAIN control, not a power control. With this in mind the only way to know what happened to make the fuse blow is to take measurements. The fuse CERTAINLY wouldn't blow at three quarters POWER into a 100% low load so I have to assume that the amp was indeed making full power, and more due to clipping. Since that could mean greater than 200W peak into the Two Notes I have to wonder if the fuse blowing wasn't the result of something shorting in the attenuator, worsening the load mismatch and causing the harsh tone. Since these are the analogous events. Perhaps the amps and the cabinet are fine and it's the two notes that is broken. That's why I suggested trying everything out as it was BEFORE the two notes unit was added. But, of course, no one would ever want to believe that their new, cool thing is a problem. Or even worse, that they may have broken it!