Prima Luna Prologue 3 rolled some tubes and...

My 2 channel system is pretty modest. The room upstairs is small and shaped entirely wrong. My budget is limited. I swap stuff regularly. A lot of it. When I coupled my Job 225 with a Prima Luna Prologue 3 something exciting happened. It was audio nirvana, a gorgeous balance of the Jobs lightning fast attack and high end sparkle coupled to the PL's laid back tube sound. My current speakers are LSA 1 Statements. The PL had new matched Gold Lions in it. As fate would have it, I bought a hand full of Amperex Bugle Boy 12ax7, 12au7 and some Telefunken 12ax7 tubes, along with some old equipment from an estate. I paid $200 for all of the equipment and the tubes. So my wee little brain thought, tube rolling? It might just work. Sure enough the tubes tested well and after about 5 minutes of warm up my jaw hit the floor. My oh my, what a change! After a day of swapping things around I settled on a pair of 12au7 Bugle Boys, a pair of 12ax7 Telefunkens and the Gold Lion GZ34s. The soundstage gained height, width and depth. The instruments and vocals had more air, but were also more focused in relationship to each other. Highs are clean and warm. Bass is solid and tight, but a tiny bit lean in the lower frequencies. My wife walked in and she asked what I had done to system.  In my mind, if I had spent $1k to get this much improvement it would have been a bargain.  So here are my questions...

1. How/why do tubes made in the 1950's (Amperex dated 1949 & 1950) sound better than my modern Gold Lions?

2. Is there a better combination out there?

3. Since swapped tubes make a huge difference what would happen if I swapped out capacitors, resistors etc?
Welcome to tubes. The difference is not subtle, is it? Combo looks good. Look at 5751 instead of 12AX7. Different theories on old tubes: simply better made with more attention to detail and tolerences (military spec), using materials that used processes not allowed today due to toxicity. Quality over profit maximization.
Yes, better passive components will bring benefits as long as you don’t change the voicing of the amp from the designer’s intentions.

Amperex and Telefunken are considered top shelf tubes.  There may be a better combination out there but I couldn't tell you what they would be.  Some other PrimaLuna owners will probably chime in. 

If you're willing to spend some money, call Kevin Deal at Upscale Audio.  He is the PrimaLuna importer and has a large stock of NOS tubes.  He is very knowledgeable about both.  You can check out the Upscale Audio website to see what kind of prices we're talking about.

I agree with trying 5751s.  I prefer the 5751 in most cases where the somewhat lower Mu is compatible with the other elements most people run. .  In your case I think it will work just fine.   I think your jaw may drop further with them, because I find them to have an even larger  and more imaging - soundstage.

The caveat is that 5751s produce about 70% Mu compared to a typical 12AX7. That means that they may not be sufficient to work with other parts of your system.  High gain  phono stages where the gain is critical,  such as in an MC stage.  

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I should mention these tubes were never used; they were back-ups for the the pair I had in my Primaluna Dialogue One, since SOLD to another very happy Audiogon member. Best, Rob

My Gold Lions came from Kevin. The PO had just bought them. I have had other tube equipment but always wished for just a shade more.... 
I also had the matching PL amplifier but did not enjoy that combination at all. I ran a AVA Transcendence with the PL amp for a bit but didn't like that either. It was the arrival of the Job that got me pointed down this road. I already owned the PL preamp, I just wasn't using it. The Job tempered by the PL, gave me that..... I was looking for. The NOS tubes sent this combo over the top. Way over the top. I used to sell audio back in the day. I have never seen such a change in sound, other than a significant upgrade in speakers. 

Caveat emptor. In another post I talk about my hearing loss and constant tinnitus. Others might think my set-up too, too, something or other.

I might swap to 5751 tubes but I will wait until I get the urge to roll again. Right now Patricia Barber is singing "Touch of Trash" and she is standing in the middle of my room.
try some better coupling caps. That amp will surprise you.

I have the PL Dialogue Premium integrated . I don't know how much of a difference that would make in the evaluation .

In place of the stock 12AU7's you might try some RCA clear tops . I liked these quite a bit for warmth , clarity , definition and musicality . If these RCA's are to your liking , then try some Amprex 7316's . They are like the RCA's on steroids but more expensive . The 7316's are what I settled on after trying most of the others .

Happy Tunes

try some better coupling caps. That amp will surprise you..

I have had a Prolouge P3 and P5 shelved for some time, with the intent of possibly changing the coupling caps.  Is the mod you recommend based on first hand experience or is it more of a general observation of better caps/components = better sound. Provided you personally had this or other mods done to PL equipment, would you please forward who performed the mods, and a means of contact. I would like to talk to them regarding modification of my equipment.

Thank You