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Amp Impedance Question

Excalibur

Member
Joined
Jun 12, 2003
Messages
435
My Marshall '72 Super Bass has a stuck impedance selector and its stuck
on the 4 ohm setting,now i have two cabinets one is 8 ohm and the other
is 16 ohm,can i causae damage to the transformers by connecting my 4 ohm
amp head to those two cabinets or vice versa,damage to my speakers?
that of course until ill find someone qualified enough to fix that problem.
thanks.
 

Mikester

Member
Joined
Aug 26, 2005
Messages
868
My Marshall '72 Super Bass has a stuck impedance selector and its stuck
on the 4 ohm setting,now i have two cabinets one is 8 ohm and the other
is 16 ohm,can i causae damage to the transformers by connecting my 4 ohm
amp head to those two cabinets or vice versa,damage to my speakers?
that of course until ill find someone qualified enough to fix that problem.
thanks.

Short answer: No.

If you run both cabinets in parallel, that is about 6 ohms for speakers from a 4 ohm amp. No problem.

If you must run one cab, use the 8 ohm and you will still be OK.

You would run a risk of Xformer damage by running the 4 ohm amp thru the 16 ohm cab. But, I've run 4 ohm fender amps thru 16 ohm marshall cabs and never hurt the amps. (I kept the power output down on the amps.)

You can only hurt the speakers if the watts of the amp exceed the watts of a cab, and you crank the amp with lots o' distortion.
 

Excalibur

Member
Joined
Jun 12, 2003
Messages
435
Hi Mikester and thanks,i allways run half stacked and never crancking the amp
volume (i use the amp clean and get my distortion from a pedal)
what i was really worried about was the transformers rather than the cones..
the amp gets real hot,much more than my new 1959HW and i was wondering
if this is normal,thanks again.
 

JoeV

New member
Joined
Mar 14, 2006
Messages
598
What part of the amp gets hot? The OT transformer should not be too hot to keep your hand on (it will be warm, probably, from the output tubes' radiant heat). If it is, something is up. The tubes will get ultra hot in minutes, of course. PT will run pretty warm, but you should not be able to cook an egg on there, either.
 

Excalibur

Member
Joined
Jun 12, 2003
Messages
435
What part of the amp gets hot? The OT transformer should not be too hot to keep your hand on (it will be warm, probably, from the output tubes' radiant heat). If it is, something is up. The tubes will get ultra hot in minutes, of course. PT will run pretty warm, but you should not be able to cook an egg on there, either.

I really have no idea as for where the hit is coming from..can i touch the
transformers after unplugging the outlet with no life risk?..
maybe I'm just a little bit paranoid and it's a normal degree of temp
for an old amp as mine ('72) but it's sure hotter than my new 1959HW.
Thank you Joe.
 
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