Bare Knuckle Pickups Forum

Forum Ringside => Guitars, Amps and Effects => Topic started by: puma_21 on September 01, 2012, 12:59:14 PM

Title: Pulling 2 power tubes
Post by: puma_21 on September 01, 2012, 12:59:14 PM
Does pulling two tubes from the power section actually do anything besides earlier breakup and a tad less volume and headroom? Does anyone else find it changes the tonal quality?
Title: Re: Pulling 2 power tubes
Post by: HTH AMPS on September 01, 2012, 02:06:00 PM
You'll need to knock the impedance on the amp down a notch too to retain the correct primary Z.

The tone does change a little, depends on the amp - some more than others.
Title: Re: Pulling 2 power tubes
Post by: Toe-Knee on September 01, 2012, 02:33:09 PM
HTH is correct.

I find the pulling two valves to be quite redundant though. You don't really get any benefits volumewise.

The only time I ever do it is if I have some valves and one goes bad and then its only until replacements arrive.
Title: Re: Pulling 2 power tubes
Post by: richard on September 01, 2012, 02:36:22 PM
I remember reading a very convincing article about why this is not a good idea and doesn't actually accomplish what it's supposed to. Something to do with the transformer being designed to work with a specific tube complement. But no harm in trying it - let is know what you think.
Title: Re: Pulling 2 power tubes
Post by: Toe-Knee on September 01, 2012, 02:37:52 PM
If you adjust the amps impedance it works fine as HTH said the primary Z is then correct.

Oh yeah don't ever do it on a bugera.

A friend did it and it took his OT out in less than half an hour.
Title: Re: Pulling 2 power tubes
Post by: Frank on September 01, 2012, 02:45:06 PM
The really important specification for the output transformer is the impedance ratio. Your OT doesn't particularly care if it's connected to two EL34's or four 6L6's or sixteen EL84's on the primary - as long as the speaker load on the secondary multiplied by the impedance ratio of the transformer roughly equals the required load for the output tubes then it's all the same from the point of view of those pesky little electrons.

EDIT: except in a Bugera, apparently!