removing power tubes to reduce watts

[Anonymous]

help, can remove tubes from my model t

[AdmiralB]

Is this an old ('70s) amp or the recent reissue?  In either case the answer is yes, but there are a couple of things to consider.

First, you will need run a speaker load that is numerically twice what the output requires - i.e. if you pull two tubes, you would want to run an 8-ohm cab in the 4-ohm output, etc.

Second, the voltages inside will rise somewhat - this will affect the bias, though it probably won't be a big deal.

Finally, WHICH two you pull matters.  The rule of thumb is USUALLY that you pull either the two outer or inner pairs - in any case, you would pull EITHER tube 1 or 2 AND tube 3 or 4.  I don't know about the old Model T, but the big Sunn amps built on the 1200/2000 chassis are NOT set up this way, and you would pull 1 or 3 AND 2 or 4.

[Anonymous]

On 2002-03-26 07:37, Anonymous wrote:
help, can remove tubes from my model t

                                     ADMIRAL B THANK-YOU SO MUCH FOR THE INFORMATION.MY MODEL T IS A MID 70'S AS FAR AS I CAN TELL AND IT SOUNDS LIKE NO OTHER AMP I,VE EVER PLAYED.I LOVE THE TONE IT'S JUST ABIT TOO LOUD FOR MY PURPOSES.  THANK'S AGAIN FOR TAKING THE TIME TO REPLY. PEACE BROTHER.                

[hosebeast]

so I just got a red knob T and the furthest right (when looking at the amp from the front) tube is out. I'm thinking about doing this until my new tubes get here but I have no experience with this. The tubes are asymmetrical too so I wasn't sure if I should pull the tube right next to the burnt one, or the one furthest from it.

Basically just trying to find out what the tube configuration in these is as I can't find that info on google. Are they A BB A like most typical amps or are they AB AB? thanks in advance!

[Isaac]

Another thing to remember is that pulling two tubes is only going to reduce the power by half, and that's only a 3dB drop. It's really not much of a change.

About a year ago, my old Model T took a dive off the top of my bass stack while setting up for a show. Dented the grill and damaged one of the power tubes. But the show must go on, so I pulled the corresponding tube and played at half power. The next night, I brought another pair of tubes to get me back up to full power. The difference in volume was minimal, but there did seem to be a change in tone. I think the difference was due to pushing the amp into distortion on night one. Playing at about the same volume the next night, the power section wouldn't have been pushed as hard.

Anyway, the point is that you shouldn't expect the amp to be half as loud. It won't be.

[hosebeast]

Sigh

I know the difference between wattage and volume, thanks - I have a blown power tube and since I can't afford to replace them for a minute I just wanted to pull it and it's matched brother and if it's a little easier to push then so be it.

Simply trying to figure out how the tubes are paired - whether it's 1 2 2 1 or 1 2 1 2 - like should I pull the bad tube and the one next to it or the bad tube and the one on the other side of the one next to it.

[loudthud]

The tubes are paired 1 1 2 2. So remove one from the 1 group and one from the 2 group.

[Walt-Dogg]

1s in front 2s in back?

[hosebeast]

I thought you were supposed to remove both of one? So it's from left to right (looking from front of amp) it's 1 2 1 2? So I shouldn't remove my burnt one (furthest right from front of amp view) and the one furthest left, and instead should remove the burnt one and the one right next to it? Crap! Everything I've read says to do both 1s or both 2s.

Just trying to find a definitive answer before tomorrow.

[loudthud]

The tubes are viewed left to right. It doesn't matter if you are viewing from the front of the amp or the back. The tubes are paired 1 1 2 2. So remove one from the 1 group and one from the 2 group.

[hosebeast]

My questions might be worded badly, but I was only referencing the view because of which of my tubes is burnt and to make it easier for frame of reference. I appreciate that post though. I feel like I'm asking a really specific question though and not getting a really specific answer haha. I've never had to replace a tube in my life and never really had to deal with troubleshooting due to luck I guess so I'm anxious about certain perimeters of messing with the circuit.

I think I got it - just gonna take out the one all the way to the left along with the burnt one and if it screws up I'll chuck the amp in the river - thanks, loudthud!

[hosebeast]

well I did it, took out the two outside tubes. Couldn't honestly tell if I'd messed anything up, though it seemed to break up at pretty low volume.

Hope I'm not destroying my amp!

[Isaac]

Shouldn't. You did follow the impedance advice given above by AdmiralB, right?

[hosebeast]

sure did! ran into an 8ohm cab so i cut it to 4ohms.

i have a flanger hoax on my board and it was producing some weird, weird noise that i thought was the amp, but i think it's fine.

thanks dudes!