switching from 100 to 50 watt mode
- Thread starter mwalluk
- Start date
mwalluk
New member
Re: switching from 100 to 50 watt mode
Even though the ends are lit up, is there minimal current drawing from them (compared to middle ones?).
Or is same current drawing from all, but just half?
How does it work?
Even though the ends are lit up, is there minimal current drawing from them (compared to middle ones?).
Or is same current drawing from all, but just half?
How does it work?
Re: switching from 100 to 50 watt mode
Not sure what amp you have, but I looked at a Legacy schematic and as far as I can tell, when in 1/2 power mode, the cathodes of the outside tubes are disconnected from their ground, so they cannot conduct. There will be voltage sitting on the plates, but the tubes won't have any current running through them.
Not sure what amp you have, but I looked at a Legacy schematic and as far as I can tell, when in 1/2 power mode, the cathodes of the outside tubes are disconnected from their ground, so they cannot conduct. There will be voltage sitting on the plates, but the tubes won't have any current running through them.
Chickenwings
Alnico 6/8
Re: switching from 100 to 50 watt mode
they will all be lit cos of the tube heaters at the very least, but fwiw, a lot of amps dont switch off two tubes, they keep all four running but change them to triode mode so nothing will look much different to regular operation
they will all be lit cos of the tube heaters at the very least, but fwiw, a lot of amps dont switch off two tubes, they keep all four running but change them to triode mode so nothing will look much different to regular operation
jon the art guy
Nerdy Nerd
Re: switching from 100 to 50 watt mode
Can you pull two tubes?
Can you pull two tubes?
mwalluk
New member
Re: switching from 100 to 50 watt mode
Honestly I'm not sure.... but I do like the option of having them in there if either a tube goes bad or I need 100 Watts...
Honestly I'm not sure.... but I do like the option of having them in there if either a tube goes bad or I need 100 Watts...
mwalluk
New member
Re: switching from 100 to 50 watt mode
Not sure, I always switched it when it was on standby or off.
Not sure, I always switched it when it was on standby or off.
dystrust
Well-known member
Re: switching from 100 to 50 watt mode
Marshall Jubilees are the latter; half-power mode runs the power tubes in triode mode.
Switching power level on the Jubilee produces a rather loud pop, so I always switch it on standby.
Marshall Jubilees are the latter; half-power mode runs the power tubes in triode mode.
Switching power level on the Jubilee produces a rather loud pop, so I always switch it on standby.
Re: switching from 100 to 50 watt mode
I used to have one of those. I believe the amp goes from pentode to triode when you make the 1/2 power switch.
I used to have one of those. I believe the amp goes from pentode to triode when you make the 1/2 power switch.
Edgecrusher
New member
Re: switching from 100 to 50 watt mode
Why do that? You have to drop your ohms when you do that. Just keep the tubes in and flick the switch.
Why do that? You have to drop your ohms when you do that. Just keep the tubes in and flick the switch.
Re: switching from 100 to 50 watt mode
I don't believe that is correct. Check the schematic, and you will see that when the 1/2 power switch is engaged, it disconnects the cathodes of the two outside tubes from ground. Now, current cannot flow through the tube. I guess you could say that this is similar to pulling the two outside tubes.
http://www.carvinservice.com/crg/schematics/VL100F.pdf
Now, if you look at a Marshall Silver Jubilee 2555, you will see that in half power mode connects the screens to the plates, so the tube is now running in triode mode.
http://www.drtube.com/schematics/marshall/2555amp.gif
I don't believe that is correct. Check the schematic, and you will see that when the 1/2 power switch is engaged, it disconnects the cathodes of the two outside tubes from ground. Now, current cannot flow through the tube. I guess you could say that this is similar to pulling the two outside tubes.
http://www.carvinservice.com/crg/schematics/VL100F.pdf
Now, if you look at a Marshall Silver Jubilee 2555, you will see that in half power mode connects the screens to the plates, so the tube is now running in triode mode.
http://www.drtube.com/schematics/marshall/2555amp.gif
GilmourD
Burritotoneologist
Re: switching from 100 to 50 watt mode
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They disconnect the ability for the tubes to conduct signal but the heater filaments are still glowing.
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