Pulling tubes

[jestaudio]

Its a question i've been asked by a mate which i can't give a difinitive answer, the amp in question is a 4 tube marshall, he wants to pull 2 tubes for smaller venues, will he need to change which speaker output he uses's, my inclination is to say yes but i'm not sure which way it works

[Gibsonman63]

The short answer is yes. If I remember correctly, the output inpedance will double.

Pulling two tubes will only drop the volume down 3dB, which is not very significant. An attenuator even on a moderate setting would be much more useful.

[cbass]

nevermind

[jestaudio]

The short answer is yes. If I remember correctly, the output inpedance will double.

Pulling two tubes will only drop the volume down 3dB, which is not very significant. An attenuator even on a moderate setting would be much more useful.

your preaching to the converted, i use a THD with my mesa to get the power tubes cooking but my mate ain't got much money
back on subject the 8 ohm will then become 16 ohm, the 4 will shift to 8 etc

[tribi9]

The easy way to remember is if you pull half the output tubes all the numbers on your impedance selector will need to be doubled.

[dass101]

Removing 2 of the four tubes means you need to double the load in the secondary winding. Obviously you won't change the cab, so you need to connect the cab to the impedance that is the half of its rating. 8 ohm cab connects to a 4 ohm tap, and so on.
The difference in output volume is minimal though in this case. If you don't change the output tap you will also get a mismatch which will get you some significant volume reduction. You will also get a different tone, but that might be acceptable if the volume reduction is more important.

[Gibsonman63]

Low cost alternative 2 - Go down to hardware store and pick up a piece of plexiglass and build a screen to block the direct sound coming from the speakers. Angle it to throttle the sound hitting the audience, then on the third set when the audience has had a few beverages, kick it over, jump into a solo and dance spastically around the stage like a madman.

In all seriousness, certain speakers can be very directionally focused.

[jestaudio]

Low cost alternative 2 - Go down to hardware store and pick up a piece of plexiglass and build a screen to block the direct sound coming from the speakers. Angle it to throttle the sound hitting the audience, then on the third set when the audience has had a few beverages, kick it over, jump into a solo and dance spastically around the stage like a madman.

In all seriousness, certain speakers can be very directionally focused.

Totally agree, i tend to stand off axis when i play anyway but with a 4x12 you've got no chance give me a small 50 watt combo anyday, stacks look good but cripple your back and deafen your ear drums

[TUBEDUDE]

When my back was stronger i used a Super Reverb exclusively. It was way too loud in small venues and those tens would beam highs stong enough to shave hair. To remedy this, i would face the amp to the rear of the stage and rear it back on the legs. The sound would bounce off the upper rear wall to the ceiling then out to the audience. At that point the highs would be diffused and distribute evenly thru the room. i could hear myself better also.

[Cantplay]

Can't you just use the 4 ohm taps with 8 or 16 ohm load to draw less power?

John

[jestaudio]

Can't you just use the 4 ohm taps with 8 or 16 ohm load to draw less power?

John

interesting point, i'm never sure what a safe mismatch is on a valve amp, 8ohm speaker on a 4 ohm output is fine on solid state, not so sure about the same on a valve amp