I know on my dual rec its safe to take out the 2 center powretubes, is it the same way on a 6505+?
6505+ 60watt what tubes do I take out?
- Thread starter SwambA
- Start date
::XeS::
Member
It's useless. You don't get 60w if you take out 2 tubes.
Take note that your amp never reaches 120W because of bias (and volume, that's never maxed). It should be at 80W maybe
Take note that your amp never reaches 120W because of bias (and volume, that's never maxed). It should be at 80W maybe
Cheesebone
Member
- Jan 30, 2011
- 174
- 0
- 16
But, to answer the question, yes, on a 5150/6505 (II/+) you can yank either the two center tubes, or the two outer tubes. Only suggestion would be that, if you do, make sure you adjust the impedance/ohm setting on the amp accordingly. (So if you normally play a 16 ohm cab with all 4 tubes, you'll want to switch to the 8 ohm setting on the amp. Basically, cut it in half.)
You will notice an immediate change in tone, but honestly,even with only two tubes you still have to turn these things up to ungodly levels to really achieve audible power tube distortion. And if that's what you're looking for, then you're really just better off with a Hotplate or something similar.
I tried it for a while with mine and just decided I like the way it sounds with all 4 power tubes in there.
You will notice an immediate change in tone, but honestly,even with only two tubes you still have to turn these things up to ungodly levels to really achieve audible power tube distortion. And if that's what you're looking for, then you're really just better off with a Hotplate or something similar.
I tried it for a while with mine and just decided I like the way it sounds with all 4 power tubes in there.
TheWinterSnow
Den Mørke Natt
lol wut?
The amp ratting (120w) is the maximum power that the amp can send to the load measured in RMS (and that value is determined by the output transformer). Again I said RMS which means in reality a 120w tube amp will supply 170w peak before clipping will begin to take place.
On the other hand, the 80 watts you mentioned is the appropriate bias for a typical class AB amp.
Pulling two of the tubes out, you have to trick the tubes so that they think the transformer has twice the primary impedance than it really doesn't. You do that by halving the impedance selector switch relative to the cabinet you are using (the amp should have 8 ohms selected for a 16 ohm cabinet). This reduces the current in half which in turn reduces maximum peak power to the load to 85W (60Wrms) and idles at 42W.
The big benefit is that the amp will begin to saturate sooner, I have said before that the amp begins to get compressive at rehearsal volumes so running at 60W will begin power saturation about 3dB sooner and because there is less current being drawn the power supply will be stiffer resulting in a tighter less bassy tone (not a fan myself, I felt the amp as too sterile at practice volumes.
::XeS::
Member
MetalJonesy
more metal, more booze!!!
cheers for the info on that dude! always been too scared at pulling two tubes outta mine incase i blow something!!
I pulled out 2 tubes and a/b it against my 6505+ 1/12 combo, both the head and combo running into a mesa retco 2/12 and to tell you the truth the combo sounded better, less fizzy. I notice this when it was running at 120 watts, so I wanted to bring it down to the same wattage to see if the had someting to do with it.
The combo will still sound different, even if you match the wattage, since it is a different amp altogether.
And just so people know, you can pull 'any' tube from 'either' side. Doesn't have to be the 2 outer or 2 inner tubes per say, but it's just easier that way. As long as there is at least one tube for each side of the push pull scheme, you are good to go. Also, you won't hurt the amp at all by not halving the impedance, but it is the 'correct' way to do it. You may notice you like the tone better with the impedance mismatch. I know everyone preaches not to mismatch impedance with tube amps, but it really is ok to a point. But if it worries you, just halve it
And just so people know, you can pull 'any' tube from 'either' side. Doesn't have to be the 2 outer or 2 inner tubes per say, but it's just easier that way. As long as there is at least one tube for each side of the push pull scheme, you are good to go. Also, you won't hurt the amp at all by not halving the impedance, but it is the 'correct' way to do it. You may notice you like the tone better with the impedance mismatch. I know everyone preaches not to mismatch impedance with tube amps, but it really is ok to a point. But if it worries you, just halve it
Cheesebone
Member
- Jan 30, 2011
- 174
- 0
- 16
The combo's sound better than the heads in stock form also because the power tubes are biased much hotter in the combos, for whatever reason. When my 6505+ was stock, I measured the bias at about 17mA from the factory. That's COLD, lol. The combos (from what I read) generally sit closer to 27mA.
After a resistor swap and a little tittie-twisting on the bias control knob, I have mine pulling about 40mA right now and it sounded MUCH better than before, a lot of that hissy shit completely vanished.
(What you're hearing is an absence of crossover distortion, which is why it sounds more clear)
As for "You can pull any tube you want" - the point is that, when you see how it's wired, you learn that the two left tubes and the two right tubes are fed through independent circuits. When one "side" has an "upward" swing in amplitude, the opposite side has a "downward" swing, and it's partially the job of the Phase Inverter to maintain that balance. When you yank both left tubes out, that whole process stops and the tone will change, likely for the worse. (At least from what I understand)
*EDIT* upon rereading, I realized you said 'any tube on either side as long as you have one one on each side', lol sorry. *facepalm*
After a resistor swap and a little tittie-twisting on the bias control knob, I have mine pulling about 40mA right now and it sounded MUCH better than before, a lot of that hissy shit completely vanished.
(What you're hearing is an absence of crossover distortion, which is why it sounds more clear)
As for "You can pull any tube you want" - the point is that, when you see how it's wired, you learn that the two left tubes and the two right tubes are fed through independent circuits. When one "side" has an "upward" swing in amplitude, the opposite side has a "downward" swing, and it's partially the job of the Phase Inverter to maintain that balance. When you yank both left tubes out, that whole process stops and the tone will change, likely for the worse. (At least from what I understand)
*EDIT* upon rereading, I realized you said 'any tube on either side as long as you have one one on each side', lol sorry. *facepalm*
