Rolling KT150s in Primaluna hp integrated

They used the Wilson Watt/Puppy 8"s for this review.
This statement by the reviewer is wishful thinking.
" Although neither the Wilsons nor the Franco Serblin Accordo’s are particularly power-hungry"

Stereophile test on the WP8’s:
"However, and also like its predecessors, the WATT/Puppy 8’s impedance characteristic demands the use of an amplifier that can deliver generous amounts of current. There is a drop to 2.2 ohms at 77Hz where the most power is needed. (fig.1)"
https://www.stereophile.com/images/archivesart/607WILFIG01.jpg

Combine that 2.2ohm with the -phase angle, and it could go down even below 2ohms. And with the PL’s you’ve only got 2 tubes to drive each speaker.

Cheers George

1graber2111 posts03-10-2018 5:44am@georgehifi as you said, the bias can change the heat.

Ah no, I said the main source of heat from tube amps is from the heaters/filament it's circuit/transformer, the bias whatever it is, contributes a small amount compared to that.
Cheers George

1graber2
@georgehifi PrimaLuna emphasizes that they run their tubes about 1/2 -2/3 as hard as other manufacturers in order to NOT overrun the tubes, especially since PL encourages listeners to tube roll with expensive NOS tubes. I believe the amp also gets a more stable load and presumably lower distortion with not running the tubes so hard and hot.

Grabber, "running a tube hard or not" is just the bias setting for the tube. It has nothing to do with the heater/filament current which is the main producer of heat that comes from a tube amp.

Cheers George

Great idea George! I didn't think of that.

I would also mark them so they go back in the same position in the amp.

Cheers George  

In my case it very well may be that there was more miles on my original KT150s than I realized and that putting in fresh tubes made the difference and it had nothing to do with the cryogenic process.

The way to test this, is to send your healthy original used tubes away for cryo'ing (make make sure you get the same ones back by marking them). Then having a listen to them again.

Cheers George    

Can you guys share your experience on how hot the amp gets with those tubes?  Many thanks!

From the EL34's 6amp to the KT150's 8amps there will be substantial heater temperature dissipation, if the heater voltage stays at 6.3v and doesn't sag under the extra load that the 150's will put on the filament supply.

Cheers George  

as I'm not sure the cryo process is a good idea for tubes but that's maybe just me

It's not, all it does is weaken the tube and cause vacuum leakage.
When you freeze especially this cold, different materials, they contract at different rates, then expand back at different rates.
 
And in a tube you have glass, high temp plastic or bakelite if nos, metal pins, different metals inside nickel in nos all sorts of different materials.

Cheers George   

Thanks George. Primaluna endorses the use of KT150s.

That's good that you said, they say it's OK, because that's is then it's under warranty for owners to do it with peace of mind. 

Cheers George 

jbhiller
  Are you saying that you think it's a problem based on your personal review and expertise? I'm having trouble understanding your point.

I've had tube amps come to me for repairs on the heater circuit too many times because customers have put in more powerful tubes and not bothered to see/check if the heater has the same current draw as the tube it was designed for. They think if the tube is interchangable it must be fine. 

And in this case the KT150 can have 30% more heater current draw over the EL34, on the rectifiers and heater winding of the transformer. This sometimes doesn't show up as a fault till it's been used/cooked for a while.
Tell tail signs are the power transformer is quite a bit hotter or you can smell something that wasn't there with the EL34's 

In case you did know the hottest running section of a tube power amp is the heater circuit & filaments

Cheers George        

Had anyone who owns one of these bothered to check with the manufacture about heater current draw on the heater circuit of the amp?

As 4 x EL34's draw 6amps, but 4 x KT150's can draw 8amps, this is enough increase to cook and damage things over a period of time 6 to 12 months or so, or even shorter depending the headroom the heater circuit has. 

Cheers George