8 ohm speaker in a Twin

Louis Falardeau · Post by **Louis Falardeau** » 26 Feb 2009 7:21 am

I have a Twin that is the 135 watt ultralinear transformer type. I am wanting to use an 8 ohm speaker . Can I just put a shorting jack in the ext. speaker outlet to get on the 8 ohm tap. Thanks, Louis

Pete Burak · Post by **Pete Burak** » 26 Feb 2009 8:58 am

[edit]
Trust what Ken says!
~pb

Ken Fox · Post by **Ken Fox** » 26 Feb 2009 2:30 pm

Yes, that will work. the shorted 1/4" jack will be in series with the internal 4 ohm load and switch the output to the 8 ohm tap. Buy a darn good plug and short it well! An open circuit can and will result in a blown output transformer!!!

Louis Falardeau · Post by **Louis Falardeau** » 26 Feb 2009 3:07 pm

Thanks for the info , Louis

Jon Light · Post by **Jon Light** » 26 Feb 2009 3:25 pm

I am eternally confused by this issue. This arrangement is unique to the ultralinear circuits, yes?

Ken Fox · Post by **Ken Fox** » 26 Feb 2009 3:41 pm

Yes it is used on the UL amps and even some later amps use the Switchcraft switching jack for output tranformer tap changes (the Hot Rod Series of amps do that as well). Peavey did it as well with the old VT series of tube amps.

Jon Light · Post by **Jon Light** » 26 Feb 2009 3:54 pm

Thanks.

re: my confusion--I should have said "unique to the UL amps vs. the earlier BF & SF Fenders."

James Morehead · Post by **James Morehead** » 26 Feb 2009 8:09 pm

Ken, not to get confused over terminology, would a shorted jack be the same as a "dummy jack", open jack, or a dead plug? Dumb question from a dummy here.

Ken Fox · Post by **Ken Fox** » 26 Feb 2009 9:14 pm

A dummy jack could have the tip/ring shorted or open, depends on the need it has to serve.

James Morehead · Post by **James Morehead** » 26 Feb 2009 9:43 pm

Thanx Ken.