EL34 / KT66 SET

pre65 · Post by **pre65** » Thu Jun 17, 2010 9:59 pm

There is always the option to try KT66 in ultralinear mode if I need to, just needs a small wiring change. There is an UL tap on my Hammonds.

cressy · Post by **cressy** » Thu Jun 17, 2010 10:42 pm

ive still got mr Is 5881s if you want to try them too phil, they dropped straight in on mine. also try kt77s, i thought they were much better than the el34s or the kt66s i tried. my favourite ones were a pair of el37s though. gorgeous sound was got from those

Mike H · Post by **Mike H** » Thu Jun 17, 2010 10:57 pm

Them's would only be NOS I'm guessing, where'd you get 'em?

pre65 · Post by **pre65** » Thu Jun 17, 2010 11:13 pm

Can anyone remind me about ultra linear ?

Do I still keep the G2 resistor (currently 120R 5W) in place when connecting G2 to the UL tap instead of anode ?

cressy · Post by **cressy** » Thu Jun 17, 2010 11:14 pm

Mike H wrote:Them's would only be NOS I'm guessing, where'd you get 'em?

they were mi old mans, i think they came from langrex

Mike H · Post by **Mike H** » Fri Jun 18, 2010 12:11 am

The Aladdin's cave!

pre65 wrote:Can anyone remind me about ultra linear ?

Do I still keep the G2 resistor (currently 120R 5W) in place when connecting G2 to the UL tap instead of anode ?

I would say so.

It's purpose is to make sure screen Volts is slightly under anode Volts.

Dave the bass · Post by **Dave the bass** » Fri Jun 18, 2010 8:25 am

Mike H wrote: I would say so.

It's purpose is to make sure screen Volts is slightly under anode Volts.

Oh. Isn't there enough resistance in the TX winding to provide the same Mike or is the addition of the resistor a belt and braces option.

Just curious.

DTB

Post by **Nick** » Fri Jun 18, 2010 9:01 am

No, because there is even more of the tx winding between b+ and the anode.

Dave the bass · Post by **Dave the bass** » Fri Jun 18, 2010 10:54 am

Nick wrote:No, because there is even more of the tx winding between b+ and the anode.

Doh. Yup, of course. I see what you mean.

As you were class!

DTB

pre65 · Post by **pre65** » Fri Jun 18, 2010 11:32 am

I've used a couple of 4mm plugs and sockets to make a jumper for normal use. For UL the jumper is removed and the blue socket goes to a blue socket on the OPT.

Only just fired it up in UL and it seems to have just a tiny smidge more "weight", but will give it a few more discs before a proper opinion.

Mike H · Post by **Mike H** » Fri Jun 18, 2010 1:11 pm

This thing about the screen resistor is a bit strange, fine as a theoretical basis but, as someone pointed out on another forum anode Volts is going to be way over screen Volts on the positive half cycles!

Ditto if screen were fixed to B+. I think the conclusion was it depends how robust the valve is. In other words has to be designed with that eventuality in mind. For this reason I think power pentode screens tend not to be able to pass high current, or else the wire must be able to withstand a high temperature.

Summink like that

Mike H · Post by **Mike H** » Fri Jun 18, 2010 1:12 pm

Forgot to mention, very pretty colours Phil!

pre65 · Post by **pre65** » Fri Jun 18, 2010 1:14 pm

Mike H wrote:Forgot to mention, very pretty colours Phil!

I have used loads of those high voltage plugs / sockets and the different colours just make it easier to connect things up in the correct manner - which is nice.

Mike H · Post by **Mike H** » Fri Jun 18, 2010 1:33 pm

Yes of course, just that it's different to boring red and black. I have also used alternative colours, just to relieve the monotony

Also cos often you can't get red or black cos everyone else has bought 'em!

pre65 · Post by **pre65** » Mon Jun 21, 2010 12:54 am

It's still running with KT66 in UL mode and I like it a lot.

Perhaps tomorrow (or later today

) I will put the EL34 back in and try them in UL.

audio-talk

EL34 / KT66 SET

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