Can I run just two power tubes installed on a MKllc 60/100?

sharkinabus · Jun 9, 2007

Hi,

I only ever use my amp in the 60watt position, will I damage it if I run it with only two power tubes installed instead of four?

Is it the outside pair that operate on 60watts and the two inner ones that kick in in 100watt mode?

Cheers

Blueracer · Jun 9, 2007

I looked for a IIC schematic to no avail. I like to have backup when I answer a question. Every other Mark series amp that I looked at had a switch on the cathode of the inner two tubes to switch between high and low power. This would stop any current going through the inner tubes tubes effectively taking them out of the circuit when in low power. The only part of these two tubes that is actually functioning under these conditions is the filiment. So yes you should be able to remove the inner two tubes without any problem. Likewise in the low power mode it is the outer two tubes that are providing the power. Also from these schematics there actually would be no problem being in the high power mode without the inner two tubes being there. Of course you would only have low power but it should be conforting to know that accidentally switching to high power with the inner tubes missing will not hurt things. Hope this helps.

Gary

sharkinabus · Jun 9, 2007

Thanks for the fast reply!

Anyone able to confirm the no damage if accidentally switched to 100watt mode for the mkllc+?
I'm sure it's as per the other 60/100watt Mark series but better safe than sorry..

Cheers

strngbndr · Jun 9, 2007

What I did for awhile with my MKIIB, was to replace the On/Off 100/60 Watt toggle switch in my amp, with an On/On swith that allowed me to use either the 2 outside or the 2 inside tubes. I then used Groove Tube adaptors on the outside and a pair of 6L6s on this inside.

I have used the amp for years without any tubes in the inside 2 sockets, but cannot say for sure that the amp was in the 100W mode at the time.

Blueracer · Jun 9, 2007

sharkinabus said:
Thanks for the fast reply!

Anyone able to confirm the no damage if accidentally switched to 100watt mode for the mkllc+?
I'm sure it's as per the other 60/100watt Mark series but better safe than sorry..

Cheers

Ok in the interest of science I tried doing this with my IIC+. It is a simul-class as opposed to a 60/100 but I do believe that the switching between high and low power is the same. Ran with the inner tubes removed with the switch in both high and low positions and the amp couldn't have been happier.

Cheers,
Gary