Fender Showman

[cauger]

I'm blown away with the amp now how it is I'm sort of afraid to mess with it. I'm going to throw in the full quad tonight and get back to this thread if my house doesn't cave in on itself. 

[Professor Plum]

I'm blown away with the amp now how it is I'm sort of afraid to mess with it. I'm going to throw in the full quad tonight and get back to this thread if my house doesn't cave in on itself. 

thats the sprit! 

[cauger]

OK, I need help with something.

I swapped out the two tubes for four and played for a while. It sounded pretty good but I decided to go back to just running two tubes. I replaced the matched pair in their slots and plugged the guitar back in but got very low output. I realized that I had plugged into the Ext. Speaker (which is supposed to be unconnected) instead of the regular speaker jack. So I quickly shut the amp off and switched to the right speaker jack but still have the same problem of low output. I don't think it's the tubes since they just worked are in securely, did I do something by plugging into the (supposedly disconnected even though I heard sound) jack?

[cauger]

Hm... that's a tricky one.

Running the amp with no load will definitely put a strain on the output transformer if you do it for very long.  By running it with just two tubes, you were already creeping toward the edge of "safe" (though you were squarely in "safe" territory, still, provided the impedance of the cab matched).

How long was it running that way?  Did you smell any funny smells or did anything get really hot?

How about making sure it's all hooked up right and putting the quartet of tubes back in again?

Well I basically took all the tubes and put them back in and it's back to working. I think one of the preamp tubes was loose.

Now, the only cab I have is 16 ohms. My Showman has a Mercury Magnetics Twin transformer that's 4 ohms, so with two tubes the amp is working at 8 ohms, right? I usually run the amp 7-10, am I going to be "safe" doing this or am I pushing it?

[cestlamort]

maybe it's worth rewiring the cab to 8 ohms, if you can.

[cauger]

maybe it's worth rewiring the cab to 8 ohms, if you can.

Yeah, my decision is to go 2x12 or 2x15 in 4 or 8 ohms now.

I've heard some people describe the JBLs as 'ice picky', is that accurate?

[øøøøøøø]

I've heard some people describe the JBLs as 'ice picky', is that accurate?

Not to me.  I've never heard that before, either, frankly.

They do respond to frequencies above 4000 cycles, unlike most 15" speakers.  But I don't know if "icepicky" is the word I'd use to describe it.

[cauger]

Here's another question, it seems the Dual Showman has a reputation as a very loud amp. With this head the sound doesn't really come alive until it reaches 5-6 and below that it sounds pretty anemic. The sweep of the volume seems to really start at 5 and go to 10 whereas on my AC-30 it seems more linear. Is this normal or why would this be the case?

[øøøøøøø]

Here's another question, it seems the Dual Showman has a reputation as a very loud amp. With this head the sound doesn't really come alive until it reaches 5-6 and below that it sounds pretty anemic. The sweep of the volume seems to really start at 5 and go to 10 whereas on my AC-30 it seems more linear. Is this normal or why would this be the case?

That would be the case as a result of the impedance mismatch between the amp and the cab. 

In order to perform their best, an amp and its load (speakers) should be impedance-matched.

Oh, and I realized the 'best' adjective to describe JBL high-end relative to other guitar speakers... "glassy."  Not "ice pick," but "glassy" yes.  Make sense?