Rolling KT150s in Primaluna hp integrated

I’m a mere five hours into these.  This is an alive and kicking tube.  It’s like it had a double espresso before the music starts.  I’m hearing big and strong delivery, but that’s so overwhelming that I cannot focus on midrange.  It’s clear I need some time with these. 
I’m on day three of running these tubes constant.

The KT150’s power is unquestionably present. There’s more of everything while the speakers are controlled by the amplifier. Bass is more robust than any other power tube I’ve used. Highs soar. Midrange is big, BUT the midrange is not as thick and creamy as EL34s/7581s.

If someone were asking me what KT150s sound like in a Primaluna amp, I’d say that it’s definitely something worth and necessary to hear for yourself. The difference in sound (bass, highs, and control) with the KT150 is so stark it’s like listening to a different amplifier than I’m used to. There’s so much to like with this different setup.

I’m curious to see how these break in and how much I’ll miss that darker, syrupy midrange of the EL34 and variants--which I love and am very used to.

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   
Yes, georgehifi, Primaluna endorses the use of KT150s in this amp.  

Many folks run these in Primalunas without issue. 

Are you saying that you think it's a problem based on your personal review and expertise?  I'm having trouble understanding your point. 
  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        
Thanks George.  Primaluna endorses the use of KT150s.  With your background, you may be interested to see how they run their tubes and how sizable the power transformers are for the application.  
My KT150 got an endorsement from my wife. She said that they look like my speakers, Vivid Audio 1.5. 
Nice to know that they are a visual as well as audio match 🤣
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 
I prefer the sound of KT120s over 150s (I used 'em in both a push-pull and a single ended amp, the use of which was approved by the manufacturers of both amps) for reasons I can't explain as they're subtle, or I can't remember what they are. Something about the sound of the music when listening to it (take THAT pesky reviewers!). I like the "look" of 150s more…they're cool…however, another plus is that the 120s are relatively inexpensive these days.
That’s interesting Wolf. I’m thinking the 150s sound a bit more solid state—in good ways and bad. They seem to be a marvelous tube in their own right. 

Now you have me wanting to hear the 120s too. 
Jb I feel the KT 150 tube is about as ideal an output in a pp design for my purposes. I recently installed a matched quad of cryoed 150s in my quicksilver silver 88s for further refinement, such subtle nuances were further revealed. Don’t really know what is going on but I can’t imagine things getting much better. I hear no downside but then again tubeoholics have different goals and values in what their focus is. It is definitely not a "tubey" or unduly colored tube for those inclined toward that end. It just sounds more like real music to me.

I appreciate exactly what you are saying.  I think the KT150s are super musical. They are as close to neutral in coloration that I've heard in power tubes.  

Like I said…not sure why but in the amps I used them in (a factory upgraded Jolida 502P, and a Dennis Had "Inspire Fire Bottle" single ended thing) they were too similar to the 120s…since I sold the 150 quad with the Jolida amp I might still try a fresh pair of 150s at some point, but for the Had SEP amp I still have fresh Gold Lion KT88s, Sovtek KT88s (Which are sort of great sounding) and new KT120s…so I'm in no hurry I guess.
If you do go back to the 150s Wolf, try the cryoed, not too much more, less than 400.00 for a matched quad. Got them off a vendor on eBay. They biased very close, very nice tubes. I also have a matched quad of Russian Genelex Gold Lions I originally purchased for my MC-60 amps, few hours. Also tried in the Silver 88s. The uncryoed 150s had more everything, at least in those amps. The cryoed  150s caught me completely by surprise. I offered to lend to a friend to hear in his amps but changed my mind after I put them in mine first. He's getting the other ones.   
I'd love to be part of a "tube lending cabal" as I'm not sure the cryo process is a good idea for tubes but that's maybe just me…the good news is my "Fire Bottle HO" will accommodate a lot of different tubes and only needs 2 power tubes…anything from KT77s to paper towel cardboard, Fee Waybill, and Kelly Slater's wave machine.
Wolf, you are lucky and or smart. The primaluna’s 8 power tubes make cost of rolling prohibitive.  

I have tried


i really want to try 6550s, KT77s and KT120s someday. 
Wolf; if you’re bored and want to experiment on the cheap you should look at the 7581As.  Fantastic tube in my opinion. 
Oh and they glow warm blue. 
I have KT150’s in my PL Dialogue Premium HP monoblock and they are so musical. Get the KT150’s you won’t be disappointed 

Oh Wolf,  $45 from a seller I like.  Free ship for matched pair at that price, which is cheaper than a night out.
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   
George maybe you're right but then again maybe if the tube goes through the cryogenic process one may well end up with a better tube for having survived. This would be providing nothing before and after changes with regard to measurements and vacuum leakage. All I can say with any certainty is not so much about whether it works or not only that the cryoed tubes sounded better, CLEARLY. I have read some of the debate and controversy concerning this issue, seems more nay than yeah at least with regard to tubes. 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. I have to find out the parameters to test all the subjects (KT150s) on my Hickcock to see if this might be the reason or at least give me a clue. 
If your amp can run 6L6 tubes, it would be interesting to try some vintage tubes of this type.  While they don't deliver much power, I really like the sound of that type of tube.  I also like 350s, but at close to $1,000 a tube, that experiment probably will not get off the ground.
Larryi,  If only we were billionaires!  I'd finance that experiment now!

The Tung Sol 7581A is a very very good tube.  
FWIW, I briefly replaced the Tung-Sol KT120's in the CMII, and rolled in Genelex Gold Lion KT88's.  Perhaps they were slightly sweeter, but I missed the greater authoritativeness of the 120's.
I’m approaching 2 weeks into this tube roll and I have a better understanding of what the KT150s do.

The KT150s in the PL Dialogue Premium HP are a great match. It’s not easy to go back to other powertubes. I had to for a day as I dropped one when taking it out. In this amp (in my room, etc.) the KT150s just sound better. The power allows imaging and soundstage to be bigger and more controlled. The bass is without question more robust and controlled than I’ve ever heard with tubes or with 2 SS integrateds with my speakers. 

While I can’t say what others would like, I can certainly say that rolling KT150s in this amp create a big change. It’s really something owners should experience. I think the change could keep me out of the upgrade game for some time as it’s made such an improvement in sonics.

Using a combination of Mullards and Ciftes 12AU7s in the first four slots with the KT150s really dials things in to my liking.

What’s kind of surprising is the KT150s are not edgy, harsh, bright, etc. They just add more dynamics, control, authority, size and precision to imaging.

If anyone wants to buy a matched octet of Gold Lion KT88s, which I purchased from Upscale (not cyroed), PM me. They cannot have more than 300 hours on them as they are less than a year old and I ran them in rotation with 7581As, 2 types of EL34s, and now the KT150s. Such a great tube that I don’t think I’ll use with moving in the KT150s.
I totally get your excitement, I have been in the same boat with the PL HP Integrated and rolling the stock PL pre 12AU7s to NOS Mullards/NOS Brimars and the EL34--> KT88s. 

As you said, swapping out the first 2-4 pre tubes makes critical sound changes, for the better for sure. I have floor standing speakers, so my next move would be to move up to the KT120s and keep the Mullards in the first two inner pole positions of the pre tubes, followed by the Brimars, then the 2 stock tubes. Since the KT120s would spread out its energy toward the highs/low, the Mullards would fill in the mids nicely.

But alas, I live in a place without AC that gets so hot in the summer that tubes are now "temperature-prohibitive". I will be having to sell the HP integrated to go to Class D ... scary.

Same here.  I am planning to get a PL HP w/KT150 but my concern is the temperature.  Summer in Los Angeles can be as high as 107F.  Can you guys share your experience on how hot the amp gets with those tubes?  Many thanks!
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  
There is no issue with the load imposed by the 150s in this amp. The manufacturer endorses after it did significant testing before doing so.

The power transforners on this amp are massive. That’s why it weighs 60 plus lbs.

With respect to room heating, I live in Chicago so we see all sorts of temperatures from 10 below to 95 to 00 every year. Smaller EL 34 Tubes in their substitutes do not cause too much significant heating in the summer months. But it is definitely noticeable. I went the route of buying a class D amplifier last summer and moving the prima Luna to the basement.

Let me just say that after six months, I sold the class D amplifier and brought the prima Luna back up. I don’t know when I’m going to do this summer. The sound is to to die for so I’m just not sure. I might not care s out the heat. Or, I’ll buy a nice used integrated.

I didn’t have the opportunity to audition all different makes of class D amps. But the one that I did evaluate was not able to impress me long-term.

"The sound is to die for", different amp(s), same result, Jbhiller, I agree. The KT-150 tube is the difference. Temperature effect would depend on many factors, room size, amps, local, season, etc not withstanding George's technical considerations. 
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    
@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. 

@a25105 In the Sta Cruz Mtns, gets up to the high 90s and tops 100' as well. problem is, I live in an old barn converted into a home with cinder blocks under the wood siding. Absorbs heat like a mo-fo. No AC. I would come home from work and not be able to listen to my system! And no plans to move soon.
But the heat from the PL Integrated is from the tubes and the 3 Large Transformers hiding in the back under the metal cover .... 
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. Comparing test results through a Hickcock tube tester probably won't tell me all I need to know with regard to the effects of cryoing the original tubes and comparing directly.  
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  
I agree with almost everything in this review of KT150s and the PL Dialogue Premium HP.  The characteristics of the KT150 in this amp are accurately described in my view.
@georgehifi as you said, the bias can change the heat. that is why PrimaLuna has a "self-bias" to not run the tubes as hot. we can argue over specifics, but it is the essentially the same concept, of ultimately, how hard the tubes are run. The bias of any amp will effect the tube heat, not just PL. it is the manufacturers call for self-biased units, but the owners call if manually biased. In any case, it is true that tubes will live different number of hours, eg 5k vs10k, depending on the supportive electronics/bias adjustments.

@tubegroover @georgehifi . sending your USED tubes in to be cryo'ed may not show clear difference in sound. this is b/c "cryo'ing" tubes essentially hardens some metal structures of the tubes. these structures, metal pieces, etc will harden over time anyway with use. 

So there would be a bigger difference b/w 2 NEW sets of tubes, one Cryoed and one NON-cryoed. But if you are sending in used tubes for cryo'ing, I would ask:
how many hours do they have on them? what is their expected life span in the particular amp you are using? eg, if a used tube has 4000 hours on it, and the life expectancy is 5000 hours, then it will already have been "broken in", in terms of the metal structures hardening. Sending it in to be crayoned with 4k hours would not make a significant difference IMO. 
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
Guys, FYI, Christiaan Punter did a review of fitting KT150s to a PrimaLuna and then compared it to other amplifiers including the ARC Ref 75SE.  Interesting outcome.

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)"

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