Pulling Power tube Q's

Michael Murphy · March 21st, 2003, 05:22 PM

I have a 45w speaker in an enclosure that I need to test, and the only amp I have available at the moment is an old Dual Showman.

I want to see how it does with an amp with compatible power output running at or close to full power.

I can pull two of the Showman's power tubes and be in the ballpark, can't I? It's my understanding that either the outside pair or inside pair should be pulled, and that will give me about half of the normal power output w/o damaging the amp.

Is that correct? Or do I just need to wait until I have the correct amp at hand?

Don't wanna blow nuttin' up....

Thanks in advance,

-Michael
Charter Member S. Texas He-man emoticon-haters Local #316

jazzguitar · March 22nd, 2003, 03:21 PM

even with only two power tubes there may be more than 45 watts.

Michael Murphy · March 22nd, 2003, 06:54 PM

The amp is only rated at 85 watts- so I figure that would put me in the ballpark, power-wise.

My main concern is damaging the amp. I just wanted to know if this procedure is OK for it, and which pair I should remove (or if that matters).

Anybody know?

Thanks,

-Michael
Charter Member S. Texas He-man emoticon-haters Local #316

Silverface · March 22nd, 2003, 07:40 PM

If it's an 8 ohm or 4 ohm speaker you should be fine for test purposes. I'd suggest rebiasing when you do it though just to be safe. If you n

The amp is "rated" at 85 watts - but even cranked up you won't get more than about 35 watts or so out of two tubes. Vintage amp wattage ratings are almost always exaggerated...based on max power dissipation, which you can get - if you want to have your tubes last for 30 seconds or so.

If it's a vintage speaker chances are it wouldn't handle 45 watts without a recone anyway.

Michael Murphy · March 22nd, 2003, 07:53 PM

Hmmm. Guess I'll wait a few days.

Thanks for the info.....

-Michael
Charter Member S. Texas He-man emoticon-haters Local #316

March 21st, 2003, 05:22 PM	#1 (permalink)
Michael Murphy Tele-Afflicted Join Date: Mar 2003 Location: I can hit the Pacific Ocean and/or Canada with a rock from here... Age: 61 Posts: 1,068	Pulling Power tube Q's I have a 45w speaker in an enclosure that I need to test, and the only amp I have available at the moment is an old Dual Showman. I want to see how it does with an amp with compatible power output running at or close to full power. I can pull two of the Showman's power tubes and be in the ballpark, can't I? It's my understanding that either the outside pair or inside pair should be pulled, and that will give me about half of the normal power output w/o damaging the amp. Is that correct? Or do I just need to wait until I have the correct amp at hand? Don't wanna blow nuttin' up.... Thanks in advance, -Michael Charter Member S. Texas He-man emoticon-haters Local #316 __________________ *Just an analog boy in a digital world...*

March 22nd, 2003, 03:21 PM	#2 (permalink)
jazzguitar Tele-Meister Join Date: Mar 2003 Location: Germany Posts: 280	I think you can do that, but even with only two power tubes there may be more than 45 watts.

March 22nd, 2003, 06:54 PM	#3 (permalink)
Michael Murphy Tele-Afflicted Join Date: Mar 2003 Location: I can hit the Pacific Ocean and/or Canada with a rock from here... Age: 61 Posts: 1,068	The amp is only rated at 85 watts- so I figure that would put me in the ballpark, power-wise. My main concern is damaging the amp. I just wanted to know if this procedure is OK for it, and which pair I should remove (or if that matters). Anybody know? Thanks, -Michael Charter Member S. Texas He-man emoticon-haters Local #316 __________________ *Just an analog boy in a digital world...*

March 22nd, 2003, 07:40 PM	#4 (permalink)
Silverface Tele-Afflicted Join Date: Mar 2003 Location: Hermosa Beach CA Age: 56 Posts: 1,830	depends If it's an 8 ohm or 4 ohm speaker you should be fine for test purposes. I'd suggest rebiasing when you do it though just to be safe. If you n The amp is "rated" at 85 watts - but even cranked up you won't get more than about 35 watts or so out of two tubes. Vintage amp wattage ratings are almost always exaggerated...based on max power dissipation, which you can get - if you want to have your tubes last for 30 seconds or so. If it's a vintage speaker chances are it wouldn't handle 45 watts without a recone anyway. __________________ “No Chops – Great Tone” ©

March 22nd, 2003, 07:53 PM	#5 (permalink)
Michael Murphy Tele-Afflicted Join Date: Mar 2003 Location: I can hit the Pacific Ocean and/or Canada with a rock from here... Age: 61 Posts: 1,068	Hmmm. Guess I'll wait a few days. Thanks for the info..... -Michael Charter Member S. Texas He-man emoticon-haters Local #316 __________________ *Just an analog boy in a digital world...*