Doug's tubes and 4xKT77 with Mark IV?

[disassembled]

It is well known that the simul class amps can handle a pair of EL34's/KT77's in the outer sockets. What you need to find out is if the amp will be fine if you add two more to the middle sockets. With the size of the power tranny I would say yes. I haven't done the math to see if the amp can take about 1.2 more amps of current draw but it doesn't look like it would be overkill.



OT: So are you keeping this one or are you still deciding?


Greg

 

[Paul Secondino]

After reading the following description of KT77 on http://www.dougstubes.com, I emailed Doug as well as eurotubes.com asking about the possibility and safety of running 4xKT77 in a Mark IV. I'll post responses as soon as I get them. stay tuned...


I finally got a chance to really listen to
this new tube from JJ Electronics based on the original from M.O. Valve
Company, and really like it. For the most part these will bias up like the
EL34/6CA7, but looks like around 10% of them have high enough natural
current draw to replace a 6L6 or 6550(Check with your amp tech to see if your
particular amp's 6L6 transformers can handle the additional filament
current). I installed a pair in the center sockets of my Roccaforte Custom
30 amp, and let them rip. Expect to hear crystal clear 3-D cleans,
extended lows and highs, and very thick articulate breakup.

For the most part, the EL34 and KT 77 should have more filament current needs than a 6l6. A 6l6 draws more plate current however.

So generally, you can run El34's in the inner sockets but they will run very cold . So there's no point in doing it since they will sound like crap there.