KT 88's in Mark IV ?

[Metalheart]

I am thinking about buying MK IV and need to know if anyone knows if I could use the KT 88 tubes? I need 2 1/4'' from center to center of the tube socket. The KT 88's are 2 1/8 in diameter.
That could make some noise with some JJ KT 88s in MK IV!

 

[adrenaline junkie]

There really isn't enough room. I just tried to stick a KT-88 in my Mk IV, and it wouldn't even go in straight because the side of the tube was hitting the fan.

 

[jamme61]

If you have the combo they fit. i have two JJ's that i was going to try in my MKIV but I'm worried I might blow something because they drain more heater voltage then 6l6's or el34'. I'm afraid after a while they could burn out the transformer. I could be wrong about this, but I didn't want to take a chance.

 

[Metalheart]

Bob at Eurotubes says that on a large box head MKIV ,it will hold two 88's
in the two middle sockets. What is a large box head MKIV ? That is what I am looking for. You need to look on his site and read some off his stuff on what tubes can be used on MESA amps. The guy knows his stuff!

 

[jamme61]

the large box head is just wider. Like the wide body combo vs the standard size. Bob is a great guy and knows his stuff, but I'm still a little worried about running KT88's in a MKIV. The other problem is getting them to bias right in the MKIV. I have used KT'88 in marshalls and a 5150 and have noticed more bass and more headroom.

 

[Metalheart]

Bob says even Boogie amps could use bias ajustment. First take amp to be modded by installing trim pots. All MESA's are bias a little cold and coud benifit from this. What he says makes sense,or does it?

 

[jamme61]

The bias thing gets tricky. If your running kt 88's on the outside and 6l6's on the inside, you have to try and bias everything to be within it's own safe bias range. Then you throw in class A or tweed power, and it gets even tougher. It's a real pain in the ARSE. In the end it's always a compromise, which is the way Boogie made it.