Crucial TUBE question

@czarivey -  Are you stating the use of any tube in a generic way , meaning if you were doing say a dyi build that you could design the circuit to accommodate any tube as a rectifier? Otherwise, I remain hard to convince that you can arbitrarily swap any tube as a rectifier into a manufacturers circuit that was designed with specific rectifiers  in mind. In the Op's case apparently the folks at Upscale, whose owner has a long standing hands on relationship with Prima Luna ,didn't give the all's okay to swap in KT150s.  I'm not being argumentative I'm just trying to better understand your position.

I did indeed use 2 KTs in the 2 available rectifier slots. The pins actually did fit in the available holes. I had robust, deep bass and sparkling highs for the brief time I had them in. No exaggeration, the soundstage doubled, the sound was tactile. But after all of this great feedback (very positive I might add, and I thank you), I realize I just had impossible dumb luck in not blowing up my preamp. I truly appreciate all your educated ideas to help me understand the “why” of it all. I now have new 5r4gy’s in. Sounds good, but not any way near as good as what those power tubes produced. Thanks all!

@audiodidact 

@mulveling has confirmed my read that the heater would not be hooked up.  (needs both pins to have a circuit).  So KT150 would not light up and would not produce any current. 

At this point I don't think we need someone with tube knowlegde, we need someone with a primaluna schematic to figure this out.  

We all agree you should not have done any damage.  We don't understand why you got music.  

One other thing to check, follow your cables and make sure the preamp is actually in the signal path.  I assume it is as you must be using it for volume control if nothing else, but you could be using your DAC or Roon.

Jerry

@carlsbad2

I know! But everything checks out: the PL is in the signal path alright, volume control for all sources, turn off the PL = no sound and vice-versa. The KT 150s lit up as well (mostly at their tops, because KT105s don’t glow much because of how they are constructed). I’ll say this, not as an excuse, because i should still have checked further: but Upscale promoted the KT 150 as being compatible with “all” of their Prima Lunas. There is no where on there tube info dictating to NEVER place a KT150 into a PL preamp. But, in fairness to them, they probably assume no one’s that stupid. What made me stop to ask them when everything was going great as far as I knew? I couldn’t find any posts, reviews, reports, ANYWHERE about using the KTs the way I did, only with integrateds and amps. It spooked me, so I wrote Upscale about it. Glad I did,and glad I posted about here too. All of you are being super helpful. But, still don’t know how come it worked.

Are you sure you aren't using the Home Theater bypass inputs?

But looking at the underside photo on the web site, it actually *is* possible that the KT150 worked.  There's a zener or diode wired from pin 8 to pin 7 on the rectifier sockets, and that's where the B+ is taken from. Maybe the the KT150 was acting as a half-wave rectifier, with the screen as the plate?  It wouldn't be elegant but it might work.

I will say, I have to hand it to PrimaLuna for designing a preamp that's fool-proof enough that dropping a totally inappropriate tube into the rectifier slot doesn't result in a catastrophy. ;-)  No knock on you, audiodidact.  It happens.  Much worse damage can occur when an octal tube's key is broken and the tube gets inserted in ways that can cause some serious damage.  It's possible the KT150s could have continued to operate that way, but it wouldn't be wise.  Sorry you lost the magic, but best to stick with a true rectifier tube.

But speaking of magic, you might want to try a pair of Mullard GZ32's.  Should not cause any problems, and that's a really magical rectifier, IMO.