KT66s in Simulclass amp

[Squigglefunk]

any problem with running KT66 tubes in the outside "class A" slot of my boogie mk IIB simulclass?

 

[RussB]

Will they fit?

 

[Squigglefunk]

Will they fit?

yes ... barely

 

[Boogiebabies]

I tried a #6 GT KT66HP in the Simul sockets and they drew 70ma at idle.
Way too high for a 25 watt tube. GT may say its a 30, but it cannot handle it. You would have to find a cold pair. I bias them in my SLO 100 as a 25 watt tube. If you try them at 30 watts the plates will start to go glow orange.

 

[Squigglefunk]

I tried a #6 GT KT66HP in the Simul sockets and they drew 70ma at idle.
Way too high for a 25 watt tube. GT may say its a 30, but it cannot handle it. You would have to find a cold pair. I bias them in my SLO 100 as a 25 watt tube. If you try them at 30 watts the plates will start to go glow orange.

I have #5 GT KT66HPs in the outside socket. No red plating or weird glowing. I've been using them this way for quite some time... is there any risk of harm to the amp? I would be sad if I burned up $50 tubes but not as sad as if I burned up my boogie.

 

[Boogiebabies]

Without a probe it would be hard to tell. If they are not glowing, you may have a set that is running allright with the bias of the amp. I popped them in a IIC and saw the ma were way up and immediatly hit the standby switch. I have three Quads, all in a # 6, so I would like to help but cannot.

 

[Squigglefunk]

Without a probe it would be hard to tell. If they are not glowing, you may have a set that is running allright with the bias of the amp. I popped them in a IIC and saw the ma were way up and immediatly hit the standby switch. I have three Quads, all in a # 6, so I would like to help but cannot.

thanks, I greatly appreciate the feedback.

All I can say is I checked the tubes regularly when I first installed them and never saw any sign of red plating or anything... in "class A" mode I cranked the amp on the clean channel to about 7 on the master and it was nice and crunchy. These GT KT66 tubes are some of my favorite "new production" tubes. Like I said though, I'm more worried about hurting the amp than the tubes.

 

[MesieBooga]

Is something wrong if my tubes are glowing? It sure looks like the outer ones (IIC+) run hotter. I've been moving tubes around a lot, but is there something I should know or watch for?

 

[RussB]

When the plates (big, flat parts in the tube) turn cherry red, that is bad. It means the tubes are running way too hot, and will shortly fail.

This is good glow. A bit of blue around the glass, and the heaters burning orange

 

[AMG1]

When some tubes seem to be glowing more than others does that mean somethings wrong? By glowing I mean like in the pics.

Let me add your tubes are glowing evenly. I'm refering to the type of glow your pics show.

 

[Boogiebabies]

When the plates (big, flat parts in the tube) turn cherry red, that is bad. It means the tubes are running way too hot, and will shortly fail.

This is good glow. A bit of blue around the glass, and the heaters burning orange

Better than any dirty mag.


If you bias the KT66 wrong they will look like the gray plates turn orange and they get hot as hell. I actuall blew a screen grid resistor on a SLO 100 with one of those KT66HP's. It went orange within 5 minutes and popped. The screen grid dropped from 470 ohms to 250.

 

[axwielding1]

Those are some damned sexy pics.....
ax. :twisted: