I have at long last opened the back to measure the stock speaker (Celestion Tube 10, G10E-30, "8 Ohm") resistance. I measure 5.7 Ohm? That is a bit low for an 8 Ohm speaker? The external speaker socket says "8 to 16 Ohm". I have not tried the amplifier with a 16 Ohm speaker yet, bur if the stock speaker impedance is rated at 8 Ohm, it might not be worth it to even try. Opinions from the amp gurus?
What I find weird, is that the internet rarely discusses the stock speaker impedance, but I have read about owners claiming it to be 16 Ohm.
The "dark" character of the amplifier had me planning a speaker swop, I fitted a new Celestion G10 Vintage, hoping that it will brighten up the amp a bit. (The DCR is 7.4 Ohm.) The G10 Vintage might have a better efficiency rating than the OEM item as well, and yes, the amplifier does sound better. A bit bright with the Dimarzio PAF 36 Anniversary pickups in my Jem Jr, but very nice with the Squier Strat. Early days, only a few soft hours on the speaker as yet, might turn out to be nice with the Dimarzio's as well when it has accumulated more time.
Still is a nice amplifier for my low volume playing, really should have a hand-wired version with a full TMB tone stack. I also still need to take out the chassis to find and check the HUM and Bias pots. Just lazy, should have done that a long time ago.